Recent Progress in the Applications of Levilactobacillus brevis in Food Fermentation: A Review

Abstract

The rising global demand for functional, “clean-label” fermented foods has driven intense interest in versatile microbial starter cultures. Levilactobacillus brevis is an obligately heterofermentative lactic acid bacterium that is highly valued for its robust environmental adaptability and exceptional capacity to synthesize bioactive metabolites, notably γ-aminobutyric acid (GABA) and exopolysaccharides (EPS). This review comprehensively evaluates the recent progress in L. brevis applications across major food fermentations. In dairy systems, L. brevis is most effective in co-cultures, where partner starters compensate for limited proteolysis and acidification, enabling improved texture, aroma profiles, and GABA enrichment. In fermented meats, selected strains contribute to nitrite reduction, flavor formation, and bioprotection, supporting nitrite-reduced strategies while maintaining sensory quality. In fish and seafood fermentations, L. brevis shows promise for controlling spoilage indicators and biogenic amines (notably histamine) in high-salt environments, although strain compatibility in mixed cultures is product-dependent. In plant-based matrices, outcomes are strongly constrained by acidity and nitrogen limitation; however, optimized fermentation can enhance phenolic bioaccessibility, generate high GABA levels, and enable emerging precision-biofortification approaches. Despite these functional advantages, its industrial application is frequently constrained by strain-specific technological limitations, and its use often necessitates synergistic co-culture systems, particularly in challenging matrices. Ultimately, this review highlights current research gaps and proposes future directions, including multi-omics integration and targeted strain evolution, to overcome sensory trade-offs and fully harness the biotechnological potential of L. brevis in next-generation functional foods and agricultural byproduct valorization.

1. Introduction

Fermentation is one of the most effective strategies for improving the safety, shelf life, sensory quality, and nutritional functionality of foods through microbial biotransformation. The rising global demand for functional and health-promoting fermented foods has accelerated the search for versatile microbial starter cultures. In contemporary food systems, the renewed industrial and consumer interest in fermented foods is driven not only by preservation and flavor development but also by the demand for “clean-label” bioprotection and in situ formation of health-relevant metabolites, including organic acids, bioactive peptides, bacteriocins, exopolysaccharides (EPS), and γ-aminobutyric acid (GABA) [1,2,3]. Within this context, lactic acid bacteria (LAB) play a central role because they combine technological performance with long-standing use in traditional foods and expanding use in functional product design. A major challenge in synthesizing the LAB literature is the recent taxonomic reorganization of the former genus Lactobacillus, in which many species were reclassified into multiple new genera within the Lactobacillaceae family. Lactobacillus brevis is now classified as Levilactobacillus brevis (hereafter abbreviated as L. brevis) [4].

L. brevis is an obligately heterofermentative LAB naturally found in diverse ecological niches, spanning dairy, meat, seafood, plant, and cereal environments [5]. It is highly valued for its exceptional ability to synthesize bioactive metabolites, most notably GABA, an inhibitory neurotransmitter with well-documented anti-anxiety and hypotensive effects [6]. Furthermore, its robust halotolerance, capacity to produce EPS, and ability to degrade toxic compounds, such as nitrites and biogenic amines, make it an ideal candidate for improving the safety and rheological properties of fermented foods [7]. More recently, “precision fermentation” applications have extended L. brevis beyond classical preservation toward biofortification, such as vitamin B₁₂ enrichment in fruit juices under controlled supplementation strategies [8]. As modern food microbiology increasingly prioritizes sustainable food systems and the biotechnological valorization of agricultural byproducts, L. brevis provides a resilient metabolic platform capable of thriving in complex nutrient-limited matrices [9].

Although the functional benefits of L. brevis are widely recognized, its industrial applications present diverging hypotheses and technological challenges. The technological performance of L. brevis is highly strain-specific and strictly governed by the food matrices. In dairy applications, for instance, its inherently weak proteolytic activity and slow acidification kinetics often necessitate its use in co-culture systems alongside traditional starters to achieve the desired product characteristics [6]. Moreover, researchers have highlighted a complex trade-off between maximizing bioactive yields and maintaining consumer-acceptable sensory profiles, and conditions favoring maximum GABA production can sometimes lead to excessive acidity or the development of undesirable off-flavors [10].

However, safety remains a primary concern. Although the European Food Safety Authority (EFSA) includes L. brevis in its Qualified Presumption of Safety (QPS) list, reflecting its long history of use, this status does not negate the need for rigorous strain-level validation [11]. In practical applications, particularly for strains isolated from traditional or environmental sources, it is essential to verify the absence of clinically relevant acquired antimicrobial resistance determinants and biogenic amine formation potential. This is especially critical in matrices such as meat, fish, and seafood, where amine accumulation is a recognized hazard. Accordingly, modern starter development increasingly integrates genomic and phenotypic screening for safety, technological robustness, and targeted functions (e.g., antimicrobial activity, biofilm/EPS-related performance, and stability during processing and storage) [12,13].

The primary aim of this review is to comprehensively evaluate the recent progress in the application of L. brevis in diverse food fermentation sectors. By critically analyzing both single and co-culture fermentation strategies, this review elucidates the metabolic synergies, functional contributions, and current technological limitations of this species. This review highlights existing research gaps and proposes future directions, such as the integration of multi-omics approaches and targeted strain evolution, to fully harness the potential of L. brevis in the development of next-generation functional foods.

2. Physiological and Metabolic Traits of L. brevis

The technological versatility of L. brevis in food fermentation is fundamentally rooted in its distinct physiological and metabolic machinery, which allows it to transition from rich dairy matrices to complex nutrient-limited environments. As an obligately heterofermentative lactic acid bacterium naturally found in diverse ecological niches [5], it lacks the complete Embden-Meyerhof-Parnas pathway and relies exclusively on the phosphoketolase pathway for carbohydrate catabolism [14]. Through this pathway, hexoses and pentoses are metabolized into a mixture of lactic acid, acetic acid or ethanol, and carbon dioxide [5,14]. The generation of acetic acid and ethanol is highly significant in food fermentation, as these compounds act as critical flavor precursors and contribute significantly to the antimicrobial bio-preservation of the final product [15]. Furthermore, its robust ability to utilize a broad spectrum of sugars positions L. brevis as a resilient metabolic platform capable of thriving in complex matrices, making it highly effective for the biotechnological valorization of agricultural byproducts [9].

One of the most industrially valued metabolic features of L. brevis is its exceptional ability to synthesize bioactive metabolites, most notably GABA, an inhibitory neurotransmitter with well-documented health benefits [6]. The biosynthesis of GABA is driven by the glutamate decarboxylase (GAD) system, which typically comprises a glutamate decarboxylase enzyme and a membrane-bound glutamate/GABA antiporter [16]. Biologically, the GAD system functions as a primary defense mechanism against severe acid stress [17,18]. The irreversible α-decarboxylation of L-glutamate into the more alkaline GABA consumes an intracellular proton, effectively buffering the cytoplasm and maintaining a favorable transmembrane pH gradient during active fermentation [18]. Although this physiological trait is exploited to develop GABA-enriched functional foods, L. brevis strains generally lack comprehensive de novo amino acid biosynthesis pathways, often requiring external supplementation with complex nitrogen sources or protein-rich substrates to support this intense metabolic demand [6].

Food fermentation matrices expose starter cultures to multiple environmental stressors, including low pH, high osmotic pressure, and oxidative stress. The profound influence of abiotic factors, particularly temperature variations, salinity, and oxygen exposure, on the growth kinetics and antimicrobial efficacy of LAB has been well documented in strains isolated from traditional dairy products [19]. L. brevis exhibits remarkable environmental adaptability, including robust halotolerance, with recent transcriptomic analyses revealing that exposure to acidic and oxidative stress triggers rapid metabolic reprogramming and the upregulation of molecular chaperones, DNA repair enzymes, and cell wall biosynthesis proteins [20]. Additionally, the capacity of L. brevis to produce EPS plays a dual role in its physiological survival and technological applications. In addition to improving the rheological properties, such as texture, hardness, and mouthfeel, of fermented foods [10], EPS acts as a protective cellular envelope [20]. This structure shields the bacteria from harsh environmental conditions, competitive microbiota, and bile salts, thereby enhancing both viability and bio-protective efficacy throughout fermentation and gastrointestinal transit.

3. Applications of L. brevis in Dairy Fermentation

3.1. Cheese

L. brevis has emerged as a significant contributor to cheese fermentation, functioning both as an autochthonous component of traditional artisanal cheeses and as a deliberately added starter or adjunct culture in industrial applications. This species has been identified in diverse traditional cheese varieties worldwide, including Zlatar cheese from Serbia [21], Graviera Kritis PDO from Greece [22], Karst ewe’s cheese from Slovenia [23], and Cotija cheese from Mexico [24]. This exploration of artisanal dairy microbiomes mirrors broader global efforts to isolate and characterize indigenous LAB from traditional products, such as Indonesian Dangke cheese, to discover novel strains with unique functional and bioprotective properties [25]. Recent industrial applications have focused on exploiting specific L. brevis strains as functional starter cultures to enhance the nutritional quality, produce bioactive compounds, and improve the technological properties of cheese products (Table 1).

The technological contributions of L. brevis to cheese production encompass multiple functional pathways, with strain-specific variations determining their practical utility. The L. brevis B1 strain, originally isolated from traditional Polish Bundz cheese, has demonstrated significant potential as a starter culture in acid-rennet cheeses, achieving lactic acid bacteria counts above 8 log₁₀ CFU/g throughout storage and significantly improving lipid quality indices, including reduced cholesterol content and elevated polyunsaturated fatty acid levels compared to conventional buttermilk-based controls [26]. In contrast, L. brevis DSM 32386, isolated from Italian mountain cheese, has been exploited for its capacity to produce GABA when used as an adjunct culture in co-fermentation with Streptococcus thermophilus, achieving GABA concentrations up to 91 ± 28 mg/kg in experimental raw milk mini-cheeses after 20 days of ripening, compared with 11 ± 10 mg/kg in the control cheese [27]. Proteolytic activity varies considerably between strains. For instance, L. brevis M4 isolated from Iranian Motal cheese exhibited the highest proteolytic activity among the tested isolates, with a 30 mm clear halo on skim milk agar, alongside exopolysaccharide production and acid resistance at pH 3.0–4.0 [28]. The strain SRX20, identified as autochthonous in Feta cheese, demonstrates multi-functional properties, including contributions to organoleptic characteristics and anti-Listeria activity [29], while strain M2 (KX572376) used as an adjunct in ultrafiltered Feta cheese produced the highest antioxidant activity with DPPH scavenging of 31.45% and Fe²⁺ chelating capacity of 61.42% at day 14 of ripening [30].

The sensory and quality impacts of L. brevis on cheese are complex and highly dependent on the specific dairy matrix, with technological benefits not always translating to enhanced sensory profiles. In an industrial-scale study of acid-rennet cheeses using L. brevis B1, no statistically significant differences in overall sensory quality were observed compared to control cheeses during three months of storage, despite substantial improvements in nutritional parameters. However, textural modifications were evident, with B1 cheeses exhibiting lower hardness, chewiness, and gumminess than the controls, potentially attributable to enhanced proteolytic activity during ripening [26]. In goat milk acid-rennet cheeses, L. brevis B1 contributed to an intense mature cheese odor characteristic of heterofermentative metabolism [31]. The application of L. brevis in traditional cheese production demonstrates its capacity to completely ferment lactose to below 0.5 mg/100 g, effectively lowering pH and contributing to microbiological stability [32]. Autochthonous L. brevis strains from Graviera Kritis PDO cheese exhibited good acidification capacity with pH reductions to 4.5–5.0 and demonstrated proteolytic and lipolytic activities essential for flavor development during ripening [22].

Despite these promising applications, several critical challenges and research gaps remain in the utilization of L. brevis in cheese production. The strain-specific nature of technological and functional properties necessitates the comprehensive characterization of individual isolates before industrial application; however, many studies lack detailed genetic confirmation of strain persistence throughout fermentation and ripening. The disconnect between improved nutritional profiles and neutral or inconsistent sensory impacts represents a significant challenge for commercial adoption, particularly in markets where consumer acceptance is crucial. Safety considerations remain inadequately addressed, especially for strains isolated from raw milk cheeses, with limited data on potential pathogenic bacterial interactions and toxicological safety of novel products. Additionally, although the probiotic potential of L. brevis strains in cheese matrices has been suggested by in vitro studies, it lacks robust in vivo validation in human intervention trials [26].

Table 1. Summary of L. brevis applications in cheese fermentation.

Strain	Matrix Type	Key Findings and Outcomes	References
L. brevis B1	Cow acid-rennet	Improved lipid quality indices (lower cholesterol, higher PUFA) during 3-month storage. No negative impact on sensory quality was observed.	[26]
L. brevis B1	Organic cow acid-rennet	Maintained typical pH and acidity. Produced softer, moister cheese with intense creamy aroma.	[32]
L. brevis B1	Goat organic acid-rennet	High viability (~8 log10 CFU/g). Improved lipid profile and cheese consistency (softer and more elastic). Good sensory quality.	[31]
L. brevis KX572376 (M2)	Ultrafiltered Feta	Enhanced antioxidant activity (highest DPPH and Fe-chelating activity). Increased peptide content > 10 kDa. Neutral sensory impact.	[30]
L. brevis DSM 32386	Raw-milk cheese	Increased GABA concentration during ripening (up to 91 ± 28 mg/kg in co-culture). Maintained optimal pH < 5.5.	[27]

Table 1. Summary of L. brevis applications in cheese fermentation.

Strain	Matrix Type	Key Findings and Outcomes	References
L. brevis B1	Cow acid-rennet	Improved lipid quality indices (lower cholesterol, higher PUFA) during 3-month storage. No negative impact on sensory quality was observed.	[26]
L. brevis B1	Organic cow acid-rennet	Maintained typical pH and acidity. Produced softer, moister cheese with intense creamy aroma.	[32]
L. brevis B1	Goat organic acid-rennet	High viability (~8 log10 CFU/g). Improved lipid profile and cheese consistency (softer and more elastic). Good sensory quality.	[31]
L. brevis KX572376 (M2)	Ultrafiltered Feta	Enhanced antioxidant activity (highest DPPH and Fe-chelating activity). Increased peptide content > 10 kDa. Neutral sensory impact.	[30]
L. brevis DSM 32386	Raw-milk cheese	Increased GABA concentration during ripening (up to 91 ± 28 mg/kg in co-culture). Maintained optimal pH < 5.5.	[27]

3.2. Yogurt

L. brevis has been used as a promising functional starter culture in yogurt production, primarily valued for its exceptional capacity to produce GABA and other bioactive compounds. While traditional yogurt fermentation relies on the symbiotic action of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, the incorporation of L. brevis as a supplementary or co-culture strain has gained considerable attention for the development of functional dairy products with enhanced health benefits. The application of L. brevis in yogurt involves both single- and co-culture scenarios, each with distinct technological advantages and challenges (Table 2). Single-culture applications, although less common due to the nonproteolytic nature of most L. brevis strains, have been successfully demonstrated in plant-based yogurt alternatives, where proteolytic activity is less critical [33]. However, most research has focused on co-culture systems in which L. brevis is combined with traditional yogurt starters, leveraging synergistic interactions that enhance both technological performance and functional properties. This co-culture approach addresses the inherent limitation of L. brevis, its inability to efficiently hydrolyze milk proteins, while capitalizing on its unique metabolic capabilities, particularly GABA biosynthesis via glutamate decarboxylase (GAD) activity.

The technological contributions of L. brevis to yogurt fermentation extend beyond GABA production and encompass multiple functional attributes. Strain-specific performance varies considerably, with L. brevis CGMCC1.5954 demonstrating exceptional GABA production capacity, achieving 1473.6 mg/L in optimized co-culture with S. thermophilus and L. bulgaricus at a 3:1:1 ratio, a 317.06% increase over control yogurt and 52.54% higher than previous optimization attempts [10]. The L-glutamate conversion rate of this strain was approximately 4.5 times higher than that of traditional yogurt starters, underscoring its unique metabolic advantage. Similarly, L. brevis CGMCC 1306 achieved 75.3 mg/100 g GABA in mixed fermentation with S. thermophilus at a 0.5:1 ratio, representing a 2.2-fold increase over the unoptimized conditions [34]. The synergistic mechanism underlying these improvements involves S. thermophilus rapidly producing formic acid, folic acid, and carbon dioxide, creating an acidic environment that accelerates L. brevis growth and induces GAD expression. Concurrently, traditional dairy starters provide the necessary proteolytic activity to release peptides and amino acids that support the overall microbial network [6,34]. Beyond GABA, L. brevis strains contribute to EPS production, while acid production during co-culture promotes milk protein aggregation; together, these effects likely strengthen the yogurt gel network and improve texture through increased hardness, adhesiveness, cohesiveness, and gumminess, with L. brevis CGMCC1.5954 showing particularly pronounced effects on these rheological parameters [10]. Antioxidant capacity represents another critical functional attribute, with L. brevis PML1 in synbiotic yogurt exhibiting DPPH scavenging activity (69.18 ± 1.00%) comparable to that of the synthetic antioxidant BHA at 89.16 ± 2.00% [35]. These antioxidant effects may be linked to multiple fermentation-driven mechanisms, including organic acid production, biosynthesis of bioactive metabolites such as GABA and EPS, proteolysis-mediated release of antioxidant peptides, and improved phenolic compound extractability [36,37]. In plant-based applications, L. brevis KCTC 3320 fermentation of high-protein soy powder yogurt increased isoflavone aglycones (daidzein: 179.93 µg/g, glycitein: 44.10 µg/g, genistein: 126.24 µg/g) and enhanced DPPH, ABTS, and hydroxyl radical scavenging activities to 69.65%, 97.64%, and 70.90%, respectively, after 72 h [33]. However, comparative analysis reveals that L. brevis contributions to acidification are generally modest compared to traditional starters, with single-culture fermentation achieving a pH of 4.5 versus the typical yogurt range of 4.1–4.3. This necessitates the use of co-culture approaches for optimal acid development [34].

Sensory quality and viability during storage are critical parameters for commercial yogurt applications, and L. brevis performance in these domains presents both promise and challenges. Viability maintenance was generally excellent, with multiple strains exceeding the probiotic threshold of 10⁶ CFU/g throughout refrigerated storage. L. brevis PML1 maintained counts above 6 log CFU/g after 14 days at 4 °C when supplemented with 2.5% inulin, with viscosity increasing from initial values to 1636.6 ± 5.0 cps at 5% inulin concentration after 14 days [35]. Notably, biofilm-encapsulated L. brevis showed superior survival characteristics, with only a 0.25 log reduction compared to a 3.5 log reduction for planktonic cells over 21 days, while simultaneously improving texture and taste through enhanced EPS production [38]. The sensory evaluation results were generally favorable but strain- and formulation-dependent. L. brevis CGMCC1.5954 yogurt exhibited significantly improved aroma profiles, with volatile compounds 2-nonanone and 2-heptanone identified as key contributors to enhanced odor scores [10]. Consumer acceptance of GABA-enriched yogurt produced with L. brevis CGMCC 1306 scored 7.90 ± 0.24, which is comparable to commercial yogurts, although the odor was rated slightly lower than that of commercial products [34]. Synbiotic formulations combining L. brevis with prebiotics generally received positive sensory evaluations, with 2.5% inulin optimizing overall acceptability, whereas higher concentrations (5%) led to decreased scores owing to excessive hardness and altered flavor profiles [35]. However, certain applications face sensory challenges, particularly when L. brevis is combined with strongly flavored ingredients such as ginseng, where color and flavor characteristics negatively impact consumer acceptance despite enhanced functional properties [39].

A critical analysis of the current literature reveals several research gaps that warrant attention. First, while co-culture strategies effectively bypass the nonproteolytic limitations of the strain, optimal strain ratios and fermentation parameters vary considerably across studies, indicating that strict strain-specific optimization is essential [40,41]. Furthermore, a delicate trade-off exists in yogurt matrices between maximizing GABA yields (e.g., via extended fermentation or monosodium glutamate (MSG) supplementation) and maintaining sensory quality, as these conditions can inadvertently induce excessive acidification or off flavors. Second, comparative studies directly evaluating L. brevis performance against other GABA-producing LAB (e.g., L. plantarum) in identical yogurt systems are limited, hindering objective assessment of strain superiority. Third, the mechanisms underlying EPS production by L. brevis in yogurt remain poorly characterized at the molecular level, despite the clear evidence of texture improvement. Finally, long-term stability studies extending beyond 3–4 weeks are scarce, leaving questions regarding commercial shelf-life viability unanswered. Future research should prioritize the development of targeted L. brevis strains through adaptive evolution, conduct systematic multi-strain comparisons under standardized conditions, elucidate EPS biosynthesis pathways, and investigate consumer acceptance across diverse cultural contexts.

Table 2. Summary of L. brevis applications in yogurt fermentation.

Strain	Matrix Type	Key Findings and Outcomes	References
L. brevis CGMCC1.5954	GABA-enriched yogurt	High GABA yield (1473.6 mg/L). Significantly improved texture (hardness, cohesiveness) and aroma profiles (2-nonanone, 2-heptanone).	[10]
L. brevis CGMCC 1306	GABA-enriched yogurt	Achieved 75.3 mg/100 g GABA. Maintained high viability (>8 log10 CFU/mL), optimal viscosity, and sensory acceptance over 3 weeks.	[34]
L. brevis PML1	Synbiotic yogurt (inulin)	Maintained high viability (>6 log10 CFU/g). Enhanced antioxidant and antimicrobial capacities. 2.5% inulin optimized texture.	[35]
L. brevis KU200019	Synbiotic yogurt (FOS)	Increased ACE inhibition and ROS scavenging. Enhanced immunomodulatory activity. Sensory properties remained stable over 21 days.	[42]
L. brevis B7	Yogurt with ginseng	Exhibited highest antioxidant activity. Ginseng addition negatively impacted color and flavor acceptance despite functional gains.	[39]

Table 2. Summary of L. brevis applications in yogurt fermentation.

Strain	Matrix Type	Key Findings and Outcomes	References
L. brevis CGMCC1.5954	GABA-enriched yogurt	High GABA yield (1473.6 mg/L). Significantly improved texture (hardness, cohesiveness) and aroma profiles (2-nonanone, 2-heptanone).	[10]
L. brevis CGMCC 1306	GABA-enriched yogurt	Achieved 75.3 mg/100 g GABA. Maintained high viability (>8 log10 CFU/mL), optimal viscosity, and sensory acceptance over 3 weeks.	[34]
L. brevis PML1	Synbiotic yogurt (inulin)	Maintained high viability (>6 log10 CFU/g). Enhanced antioxidant and antimicrobial capacities. 2.5% inulin optimized texture.	[35]
L. brevis KU200019	Synbiotic yogurt (FOS)	Increased ACE inhibition and ROS scavenging. Enhanced immunomodulatory activity. Sensory properties remained stable over 21 days.	[42]
L. brevis B7	Yogurt with ginseng	Exhibited highest antioxidant activity. Ginseng addition negatively impacted color and flavor acceptance despite functional gains.	[39]

3.3. Fermented Milk

L. brevis has emerged as a versatile starter culture for functional fermented milk products beyond traditional yogurt and cheese applications, with documented use in probiotic milk, kefir-like beverages, and GABA-enriched functional dairy foods (Table 3). While some applications employ L. brevis as a single starter culture, most successful commercial-scale fermentations utilize co-culture systems where L. brevis is paired with traditional dairy starters such as S. thermophilus or L. acidophilus. Single-culture applications of L. brevis face significant technological challenges, particularly slow acidification kinetics and poor rheological property. For instance, L. brevis BGZLS10-17 as a sole starter resulted in very slow milk fermentation and unsatisfactory texture with lump formation, necessitating co-culture with S. thermophilus BGKMJ1-36 to achieve acceptable technological properties [18]. In contrast, co-culture systems leverage the unique metabolic capabilities of L. brevis, primarily GABA production and antioxidant activity, while relying on companion strains for rapid acidification and texture development. The non-yeast kefir-like fermented milk developed with L. acidophilus KCNU and L. brevis Bmb6 exemplifies this synergy, achieving fermentation completion within 12 h with 10⁸ CFU/mL viable cells and maintaining stability at 10¹⁰ CFU/g throughout 12 weeks of storage [43]. Similarly, L. brevis NPS-QW 145 co-cultured with S. thermophilus ASCC1275 demonstrated enhanced GABA production machinery, with S. thermophilus providing proteolytic activity and lactose hydrolysis, while L. brevis utilized the resulting peptides and glucose to induce GABA synthesis under acidic conditions [6].

The technological and health-related contributions of L. brevis in fermented milk are predominantly centered on bioactive compound production, with GABA synthesis being the most extensively documented functional property. Strain-specific GABA production varies considerably, with L. brevis J1 achieving high yields (241.30 ± 1.62 µg/mL) in adzuki bean sprout fermented milk co-cultured with typical dairy starters [44]. The GABA production mechanism in L. brevis is intrinsically linked to acid resistance, as glutamate decarboxylase (GAD) converts glutamate to the more alkaline GABA, enabling pH regulation and enhancing viability under acidic fermentation conditions [18]. Furthermore, the application of specific strains, such as L. brevis B13-2, has been shown to enhance the functional profile of fermented milk by providing robust antioxidant properties, including high DPPH and ABTS radical scavenging activities [45]. Overall, the effect of L. brevis on companion cultures appears to be matrix- and strain dependent. In dairy systems, synergistic interactions often support mutual growth and metabolic activity, whereas in some mixed fermentations, competitive or antagonistic effects may arise.

From a probiotic perspective, several formulations maintained viable counts at or above the levels commonly targeted for probiotic delivery during storage, while some products also supported survival under simulated gastric and bile conditions or after in vitro digestion, as reported for synbiotic yogurt with L. brevis PML1, skim milk with L. brevis KU200019, and fermented carob milk [35,42]. However, direct validation of probiotic functionality within finished products remains limited, and in many cases, the evidence still relies on strain-level assays rather than comprehensive product-based evaluations. Ultimately, relying on compatible co-cultures compensates for the strain’s technological limitations, allowing its biofunctional traits to be fully expressed, thereby enhancing the health-promoting profile of the product.

Table 3. Summary of L. brevis applications in fermented milk and beverage products.

Strain	Matrix Type	Key Findings and Outcomes	References
L. brevis BGZLS10-17	Milk beverage	Good technological applicability. Oral administration of product alleviated experimental autoimmune encephalomyelitis in in vivo models.	[18]
L. brevis KU200019	Skim milk (FOS)	High gastrointestinal tolerance. Enhanced antioxidant and antimicrobial activity. Maintained high viability (>8 log10 CFU/mL).	[46]
Indigenous L. brevis	Carob fermented milk	Maintained high cell counts post-digestion. Significantly increased bioaccessible phenolics and antioxidant capacity during storage.	[36]
L. brevis J1	Adzuki bean sprout milk	High GABA production (241.3 µg/mL). Good stress tolerance. Product alleviated depression-like symptoms in mice models.	[44]
L. brevis Bmb6	Kefir-like milk	Maintained high stability (~10 log10 CFU/g) over 12 weeks. Enhanced sourness. Improved colitis symptoms in in vivo models.	[45]
L. brevis NZ4	Traditional cow milk	Co-culture with yeast yielded superior sensory quality, increased organic acids, and free amino acids. Modulated yeast flavor pathways.	[47]
L. brevis NPS-QW 145	Milk fermentation	Cysteine supplementation improved GABA yield by addressing peptide availability limitations within the co-culture environment.	[48]
L. brevis NPS-QW 145	GABA-rich milk	Companion strain (S. thermophilus) provided necessary proteolysis and glucose, enabling robust GABA biosynthesis by L. brevis.	[6]

Table 3. Summary of L. brevis applications in fermented milk and beverage products.

Strain	Matrix Type	Key Findings and Outcomes	References
L. brevis BGZLS10-17	Milk beverage	Good technological applicability. Oral administration of product alleviated experimental autoimmune encephalomyelitis in in vivo models.	[18]
L. brevis KU200019	Skim milk (FOS)	High gastrointestinal tolerance. Enhanced antioxidant and antimicrobial activity. Maintained high viability (>8 log10 CFU/mL).	[46]
Indigenous L. brevis	Carob fermented milk	Maintained high cell counts post-digestion. Significantly increased bioaccessible phenolics and antioxidant capacity during storage.	[36]
L. brevis J1	Adzuki bean sprout milk	High GABA production (241.3 µg/mL). Good stress tolerance. Product alleviated depression-like symptoms in mice models.	[44]
L. brevis Bmb6	Kefir-like milk	Maintained high stability (~10 log10 CFU/g) over 12 weeks. Enhanced sourness. Improved colitis symptoms in in vivo models.	[45]
L. brevis NZ4	Traditional cow milk	Co-culture with yeast yielded superior sensory quality, increased organic acids, and free amino acids. Modulated yeast flavor pathways.	[47]
L. brevis NPS-QW 145	Milk fermentation	Cysteine supplementation improved GABA yield by addressing peptide availability limitations within the co-culture environment.	[48]
L. brevis NPS-QW 145	GABA-rich milk	Companion strain (S. thermophilus) provided necessary proteolysis and glucose, enabling robust GABA biosynthesis by L. brevis.	[6]

4. Applications of L. brevis in Meat Products

The technological contributions of L. brevis to meat fermentation encompass multiple functional roles that collectively determine product quality, safety, and shelf life. In single-culture applications, L. brevis CHOL1 demonstrated exceptional nitrite-degrading capacity, achieving 99.03% degradation in simulation systems and reducing residual nitrite levels from 3.34 mg/kg to 2.43 mg/kg in dry fermented sausages inoculated at 10⁷ CFU/g, while simultaneously promoting rapid acidification through lactic acid accumulation. This strain’s lipolytic activity was particularly noteworthy, promoting the hydrolysis of phosphatidylcholine (PC) 36:2 and PC 35:2 into lysophosphatidylcholine (LPC) 16:1 and LPC 15:1 while releasing free fatty acid (FA) 20:1, which served as precursors for key aroma compounds, including hexanoic acid and 1-octen-3-ol [49]. In co-culture applications with Pediococcus pentosaceus, L. brevis isolates from nem chua achieved optimal performance at 1:1 ratios with total inoculation levels of 6.0 × 10⁶ CFU/g meat paste, producing 10.47 g/kg lactic acid (80.14% of total acids) and reducing pH to 4.34 ± 0.07 at 96 h, while contributing to product firmness and cohesiveness [50]. Comparative analysis of L. brevis KL5 in mechanically separated poultry meat revealed strain-specific advantages in nitrite reduction, achieving the lowest residual sodium nitrite content (18.8 mg/kg after 7 days) and the lowest oxidation-reduction potential values among the tested Lactobacillus strains, while positively influencing nitrosyl pigment formation and redness (a* value) development [51]. However, critical evaluation reveals that L. brevis strains exhibit variable acidification capacity, with some isolates showing limited pH-reduction ability compared to homofermentative L. plantarum strains, potentially limiting their application as the sole acidifying agents in certain meat systems [52]. Furthermore, the heterofermentative metabolism of L. brevis may be constrained in low-sugar environments, such as mechanically separated poultry meat, potentially limiting metabolite production and functional performance [51].

The sensory and quality outcomes of L. brevis fermentation in meat products demonstrated significant improvements in flavor complexity, texture attributes, and consumer acceptance, although with some product-specific limitations. In dry fermented sausages, L. brevis CHOL1 inoculation enhanced the overall aroma profiles by increasing the alcohol, acid, and ester contents, with the unique detection of (E)-2-hepten-1-ol (fatty aroma), hexyl butanoate (fruity aroma), hexyl ethanoate (fruity aroma), and 5-methyl-2-furanmethanol (sweet aroma), while improving the hardness to levels comparable to or exceeding those of nitrite-containing controls. Consumer acceptance scores for CHOL1-inoculated sausages were comparable to nitrite controls across all criteria, with the higher inoculation level (10⁷ CFU/g) showing superior performance in aroma and taste scores, although a slight, non-significant inferiority in color acceptance was noted [49]. In Vietnamese nem chua, the L. brevis and P. pentosaceus co-culture (1:1, 6.0 × 10⁶ CFU/g) was most preferred by Vietnamese tasters for its sweet-and-sour flavor harmony, attractive pink color, and improved texture (firmness, cohesiveness), though L. brevis alone produced a highly pronounced acid taste that was less preferred [50]. Semi-dry fermented sausages containing L. brevis in various culture combinations achieved high consumer acceptance scores of 8–9 (like very much or like extremely) for color, flavor, texture, taste, and juiciness, with sensory attributes significantly enhanced by increasing fat content from 20% to 25%; however, refrigerated storage significantly decreased all sensory scores [53].

In addition to sensory enhancement, L. brevis contributes significantly to the in situ safety and bioprotection of meat matrices. Safety improvements were evident through reduced nitrite residues, minimizing carcinogenic nitrosamine formation potential, lower water activity values (0.89–0.91) inhibiting spoilage microorganism growth, and demonstrating antimicrobial activity against Escherichia coli, Salmonella Enteritidis, Listeria monocytogenes, and Pseudomonas fluorescens [49,51]. These antimicrobial effects are likely multifactorial, arising from rapid acidification and organic acid accumulation, which lowers pH and inhibits competing microorganisms, together with reduced water activity and, in some strains, bacteriocin-associated bioprotection [12,13]. Based on the studies reviewed here, L. brevis shows activity against both Gram-positive and Gram-negative bacteria; however, the current evidence does not support a general conclusion that one group is consistently more susceptible, because the outcome appears to depend strongly on strain, matrix, and fermentation conditions. The bioprotective application of L. brevis is highly relevant because these pathogens are notoriously difficult to eradicate from meat processing environments; for instance, Salmonella species can form resilient biofilms in poultry housing [54], and opportunistic bacteria like Pseudomonas recovered from poultry meat frequently exhibit multidrug-resistant (MDR) profiles [55].

However, critical gaps remain in understanding the long-term stability of L. brevis-derived flavor compounds during extended storage, the mechanisms underlying strain-specific differences in sensory contributions, and the potential for biogenic amine production under varying fermentation conditions. Notably, there is a complex relationship between the limited proteolytic activity of the strain and the accumulation of biogenic amines. Although the inherently weak proteolytic activity of L. brevis restricts its ability to generate free amino acid precursors required for biogenic amine synthesis, the presence of endogenous meat enzymes or proteolytic companion cultures can supply these precursors. Therefore, careful screening for amino acid decarboxylase-encoding genes is critical. Additionally, the slight color inferiority observed in some L. brevis applications suggests that optimizing nitrosyl pigment formation may require careful balancing of inoculation levels, residual nitrite concentrations, and fermentation parameters to achieve both safety objectives and consumer-acceptable color attributes in nitrite-reduced or nitrite-free meat products.

5. Applications of L. brevis in Fish and Seafood Products

L. brevis has demonstrated significant potential as a starter culture in various fermented fish products, including traditional Asian fermented fish (pla-ra, gajami-sikhae), fermented whole fish, and fish processing waste valorization. This species exhibits robust halotolerance and strong acidification capacity, and, unlike many of the dairy isolates discussed earlier, certain marine strains demonstrate the targeted proteolytic activity necessary for high-salt fish fermentation. In fermented large yellow croaker (Larimichthys crocea), L. brevis strain LB (10⁷ CFU/mL inoculum) as a single starter reduced histamine content by 86% compared to natural fermentation and lowered total volatile basic nitrogen (TVB-N) by approximately 30% after 8 d at 20 °C, demonstrating strong biopreservative effects against spoilage bacteria, including Aeromonas, Shewanella, and Morganella [56]. This species has also been applied to fish silage production from sea bass (Dicentrarchus labrax) processing waste, where L. brevis (10⁸ CFU/mL) achieved a pH reduction from 6.22 to 4.35 over 21 days at 27–28 °C, meeting the recommended pH 4.5 targets for safe silage production. In the spontaneous fermentation of gajami-sikhae (Korean fermented flatfish), L. brevis emerged as a dominant species at elevated temperatures (15–20 °C), showing strong positive correlations with both fermentation temperature (r = 0.523, p < 0.001) and acidity (r = 0.600, p < 0.001), reaching 100% relative abundance at 20 °C by 60 days [57].

Co-culture applications reveal both synergistic benefits and competitive dynamics that merit a critical evaluation. In pla-ra fermentation, L. brevis strain 10.5 was co-cultured with L. plantarum strain 5.25 at 5 log CFU/g inoculation levels, with both strains demonstrating halotolerance up to 15% NaCl and proteolytic activity [58]. Sensory evaluation after 6 months revealed that L. plantarum 5.25 alone achieved the highest acceptance scores for both uncooked (4.70/5.0) and cooked (4.80/5.0) pla-ra, while L. brevis 10.5 alone scored 4.60 and 4.70, respectively, and the co-culture scored lower (4.50 and 4.30), suggesting potential antagonistic interactions or suboptimal metabolite balance in mixed cultures. Histamine levels remained below the safety threshold of 50 mg/100 g for all treatments, with L. brevis 10.5 treatments ranging from 39.07 to 39.56 mg/100 g over 6 months, demonstrating effective histamine control. In contrast, co-culture of L. brevis LB with Saccharomyces cerevisiae in fermented large yellow croaker showed clear synergistic benefits: the co-culture exhibited 34% higher total acidity and 25% lower TVB-N than natural fermentation, with significantly higher lactic acid bacteria counts than L. brevis alone on days 6 and 8, and enhanced ester compound production, contributing to improved fruity and sweet aromas [56]. A similar precaution applies to fish and seafood applications, where autochthonous or wild L. brevis isolates should be verified to lack clinically relevant acquired resistance genes before industrial use as starter or protective cultures [11,12]. Future research should prioritize the comparative genomics of high-performing strains, mechanistic studies of histamine control and proteolysis, sensory-directed strain selection, and industrial-scale validation trials with techno-economic analysis. Finally, although several studies have demonstrated that selected L. brevis strains can reduce histamine accumulation, this benefit should not be generalized across species, and candidate starter cultures should still be screened for biogenic amine formation potential and other strain-specific safety traits before industrial use.

6. Applications of L. brevis in Plant-Based Fermentations

6.1. Fruit Fermentation

The application of L. brevis in fruit fermentation has progressed from simple liquid preservation to more complex metabolic engineering approaches; however, it remains highly matrix-dependent (Table 4). Similarly, the application of closely related heterofermentative species, such as Limosilactobacillus fermentum, in fruit and vegetable matrices has proven to be highly effective for targeted bioprotection and enhancement of bioactive profiles [59]. Unlike dairy substrates, fruit juices impose severe environmental stresses, such as high acidity and low levels of free amino nitrogen, which strictly govern bacterial behavior. L. brevis exhibits remarkable physiological adaptability to highly acidic conditions, achieving better adaptation after an initial decline in hostile matrices such as bog bilberry juice at pH values below 3.0 [60]. However, biochemical survival does not inherently ensure functional efficacy. For example, although L. brevis can persist in peach puree and perform malolactic fermentation, severe acid stress completely inhibits its ability to synthesize EPS, rendering it ineffective for rheological thickening [61]. Conversely, when applied in the solid-state fermentation of hawthorn fruit, L. brevis acts as an effective biological deacidification agent [62]. In a compound starter, it degraded up to 81.147% of the native citric acid while simultaneously disrupting the compact cellular ultrastructure of the fruit. This structural disintegration increases water-soluble pectin and improves overall juice yield by more than 23%, demonstrating that L. brevis in a compound starter can be strategically employed to overcome physical processing limitations in challenging raw materials [62].

The metabolic activity of L. brevis profoundly reshapes the nutritional and phytochemical profiles of plant matrices, leading to distinct biochemical trade-offs. Lactic fermentation fundamentally modifies phenolic compounds and may result in the degradation of native anthocyanins, as observed during bog bilberry fermentation [60]. In contrast, in an orange juice–milk beverage, L. brevis increased the total extractable polyphenol content and promoted the formation of novel bioactive phenolic acids [37]. Similar enhancements in antioxidant potential have been reported for substrates such as mulberry, litchi, and solid-state-fermented hawthorn fruit [62,63,64]. However, intensive microbial metabolism may pose critical safety and sensory challenges. In goji berry juice, the rapid growth of L. brevis markedly depletes essential branched-chain amino acids while simultaneously driving the accumulation of biogenic amines, raising significant food safety concerns [65]. Moreover, improper strain–matrix matching can severely compromise the sensory quality. The application of L. brevis to black grape juice resulted in undesirable acidic flavor notes and visual cloudiness, leading to consumer rejection compared to the unfermented control [66].

Despite these challenges, L. brevis remains unparalleled in its ability to accumulate secondary metabolites, most notably GABA. High-level GABA production requires external nutritional optimization because the intrinsic nutrient limitations of fruit juices cannot sustain the glutamate decarboxylase (GAD) pathway without supplementation [5]. The addition of complex nitrogen sources, such as yeast extract, bypasses the need for costly enzymatic pre-treatments and directly triggers early stage transcriptional activation of the gadB gene, enabling industrially relevant GABA concentrations in agricultural by-products, such as date processing residue [9,67]. The berry juice fermentation study [5] reported 262 mM GABA in fermented strawberry juice. Through targeted nutrient optimization, researchers have achieved industrially relevant GABA yields across diverse matrices, ranging from 3310 mg/L in mulberry juice [68] to as high as 7.48 g/L in other optimized fruit substrates [63]. While L. brevis produced substantial amounts of GABA in supplemented mulberry and strawberry juices, it exhibited very low conversion rates (~20.3 ppm) in black grape juice and markedly underperformed compared with L. plantarum [5,63,66].

Beyond basic bioconversion, L. brevis significantly enhances the functional safety, gastrointestinal delivery and therapeutic potential of fruit-based beverages. Strains selected for high gastrointestinal tolerance survive simulated gastric juice and bile salt conditions, ensuring that viable probiotics reach the intestine when delivered in matrices such as litchi, watermelon, or mango juices [64,69]. Following consumption, the bioactive compounds produced during fermentation exert systemic effects, including amelioration of TLR4-mediated intestinal inflammation in vivo [5]. L. brevis provides targeted bioprotection against food safety. It can eliminate enteric pathogens, such as Salmonella and Shigella, directly in mulberry juice [68], and its purified bacteriocin, brevicin, when immobilized on food-grade silica, effectively inactivates Listeria monocytogenes in pasteurized apple juice during ambient storage [70]. Recent advances have also positioned L. brevis as a promising tool for precision biofortification. By fortifying guava juice with cobalt precursors, L. brevis enabled the de novo biosynthesis of vitamin B₁₂ (up to 109.5 µg/L), a micronutrient naturally absent from plant-based diets [8]. This capability elevates L. brevis from a conventional fermentative microorganism to a highly versatile cell factory for the in situ production of essential mammalian micronutrients in vegan matrices.

Table 4. Summary of L. brevis applications in fruit fermentations.

Strain	Substrate/Matrix	Key Findings and Outcomes	References
L. brevis CRL2013	Strawberry and blueberry juices	Produced 262 mM GABA in strawberry juice; imparted anti-inflammatory (increased IL-10) effects to the juice.	[5]
L. brevis CICC 6239	Bog bilberry juice	Consumed sugars and decreased anthocyanins; inoculation maintained color stability during fermentation.	[60]
L. brevis NS01	Apple juice	Produced 3.2 kDa brevicin; silica-adsorbed brevicin acted as an effective biopreservative, maintaining stability across wide pH and temperature ranges.	[70]
L. brevis TMW 1.2112	Peach puree fermentate	10% fermentate addition increased viscosity 1.3-fold; preserved normal sugar and amino acid profiles without significant syneresis.	[61]
L. brevis JCM 1059T, 1061	Semi-dry date residue	Achieved 80–90% conversion of monosodium glutamate to GABA in the fermented residue.	[9]
L. brevis F064A	Mulberry juice (+MSG)	Produced 3310 ± 60 mg/L GABA; yielded high total phenolic content and antioxidant activity.	[68]
L. brevis S3	Mulberry juice (+yeast extract)	Reached 7.48 g/L GABA; increased DPPH radical scavenging 1.62-fold; maintained high final viability (~10 log10 CFU/mL).	[63]
L. brevis (LMG11437)	Watermelon and mango juices	Increased titratable acidity and enhanced red/yellow coloration; decreased total soluble solids.	[69]
L. brevis IBRC 10818	Black grape juice	Maintained ~6 log10 CFU/mL viability for 21 days; increased GABA levels; sustained acceptable sensory scores (4–5/5) for 28 days.	[66]
L. brevis (CICC 6239)	Goji berry juice	Demonstrated optimal growth and the slowest malic acid consumption among tested lactic acid bacteria.	[65]
L. brevis KU15152	Guava juice	Enabled de novo biosynthesis of active vitamin B12 (109.5 µg/L); increased lactic acid, phenolics, and antioxidant activity (DPPH 85.97%).	[8]

Table 4. Summary of L. brevis applications in fruit fermentations.

Strain	Substrate/Matrix	Key Findings and Outcomes	References
L. brevis CRL2013	Strawberry and blueberry juices	Produced 262 mM GABA in strawberry juice; imparted anti-inflammatory (increased IL-10) effects to the juice.	[5]
L. brevis CICC 6239	Bog bilberry juice	Consumed sugars and decreased anthocyanins; inoculation maintained color stability during fermentation.	[60]
L. brevis NS01	Apple juice	Produced 3.2 kDa brevicin; silica-adsorbed brevicin acted as an effective biopreservative, maintaining stability across wide pH and temperature ranges.	[70]
L. brevis TMW 1.2112	Peach puree fermentate	10% fermentate addition increased viscosity 1.3-fold; preserved normal sugar and amino acid profiles without significant syneresis.	[61]
L. brevis JCM 1059T, 1061	Semi-dry date residue	Achieved 80–90% conversion of monosodium glutamate to GABA in the fermented residue.	[9]
L. brevis F064A	Mulberry juice (+MSG)	Produced 3310 ± 60 mg/L GABA; yielded high total phenolic content and antioxidant activity.	[68]
L. brevis S3	Mulberry juice (+yeast extract)	Reached 7.48 g/L GABA; increased DPPH radical scavenging 1.62-fold; maintained high final viability (~10 log10 CFU/mL).	[63]
L. brevis (LMG11437)	Watermelon and mango juices	Increased titratable acidity and enhanced red/yellow coloration; decreased total soluble solids.	[69]
L. brevis IBRC 10818	Black grape juice	Maintained ~6 log10 CFU/mL viability for 21 days; increased GABA levels; sustained acceptable sensory scores (4–5/5) for 28 days.	[66]
L. brevis (CICC 6239)	Goji berry juice	Demonstrated optimal growth and the slowest malic acid consumption among tested lactic acid bacteria.	[65]
L. brevis KU15152	Guava juice	Enabled de novo biosynthesis of active vitamin B12 (109.5 µg/L); increased lactic acid, phenolics, and antioxidant activity (DPPH 85.97%).	[8]

6.2. Vegetable Fermentation

L. brevis has emerged as a versatile starter in vegetable fermentations, valued for enhancing health-promoting metabolites, improving safety by degrading nitrite/biogenic amines, and enriching sensory qualities. This functional enhancement aligns with broader trends in vegetable processing, such as in beetroot, where targeted microbial biotransformation is increasingly utilized to overcome the chemical instability and poor bioavailability of native health-promoting compounds [71]. Recent studies across various substrates (bamboo shoots, carrots, cabbages, pickles, etc.) demonstrate that inoculation with L. brevis (alone or with complementary LAB) can dramatically raise functional compounds like GABA and vitamins, sharply lower nitrite and amine levels, and boost flavors and textures [7,72] (Table 5).

L. brevis is often used to enhance functional metabolites. In solid matrices, co-fermentation of bamboo shoots with L. plantarum and L. brevis increased GABA content by approximately 4.5-fold compared to natural fermentation [72]. In liquid vegetable matrices, such as carrot juice, the combination of L. brevis with pectin hydrolysate prebiotics yielded massive GABA accumulations (25,000–46,000 mg/L) [73], while specific strains, such as YSJ3, have been utilized to simultaneously produce GABA and serotonin (5-HT) for targeted “sleep-enhancing” functional beverages [74].

A major advantage of L. brevis in vegetable fermentation is its ability to reduce nitrites and biogenic amines. For example, in traditional Chinese pickles, L. brevis AR123 alone rapidly reduced residual nitrite to 0.83 mg/kg (versus 17.9 mg/kg in spontaneous fermentation) [7]. This accelerated nitrite depletion has been consistently replicated across other fermented vegetable systems, including paocai [75] and carrot brines, where L. brevis inoculation significantly lowers the transient nitrite peak during early fermentation [76]. Furthermore, specific strains, such as L. brevis PK08, effectively mitigate biogenic amine hazards, reducing tyramine by approximately 66–82% in napa cabbage kimchi while simultaneously reducing histamine [77]. In essence, L. brevis starters often eliminate the nitrite peak and reduce toxic amines. This significantly improves safety without additional processing.

In addition to safety, L. brevis inoculation generally improves sensory attributes. Inoculation in sauerkraut, for instance, drives the development of higher levels of organic acids and aldehydes, leading to increased aroma and visual gloss [78]. Similarly, its application in radish paocai accelerates fermentation while yielding a crisper texture and brighter color [79], and dual-strain inoculations significantly increase ester and alcohol volatiles, enriching the overall flavor profile [75]. These flavor gains are attributed to the metabolism of sugars and amino acids into appetizing acids and alcohols by L. brevis. In addition, some trade-offs (e.g., very sharp acidity) may occur. Nonetheless, consistent reports of sensory improvement suggest that L. brevis is a valuable tool for enhancing vegetable fermentation quality.

Overall, the reviewed evidence confirms the strong role of L. brevis in improving fermented vegetables. Studies combine chemical, microbiological, and sensory analyses, lending to their robustness. However, most fermentations were performed under controlled laboratory conditions (fixed salt %, defined starter inoculum, and fixed temperature). Real-world fermentation may face variable product chemistry, mixed flora, and scale-up challenges. For instance, Chen et al. [72] found that bamboo-shoot findings may not directly transfer to other plant bases without retuning conditions. Similarly, the beneficial effects of L. brevis on nitrite levels in pickles and kimchi are clear but rely on careful inoculation and monitoring. Reproducibility may be compromised if wild flora re-emerges or if sanitation is suboptimal. Moreover, the long-term stability (shelf life) and consumer acceptance of new flavors or product textures have seldom been evaluated. Future studies should test L. brevis starters in pilot-scale fermentation and different recipes and compare starter-driven fermentations to industry norms.

Table 5. Summary of L. brevis applications in vegetable fermentations.

Strain	Substrate/Matrix	Key Findings and Outcomes	References
L. brevis	Carrot juice (+pectin hydrolysate)	Produced high GABA concentrations (45,890 mg/L) with 4% pectin hydrolysate supplementation; enhanced total phenolic content, antioxidant activity, and organic acids.	[73]
L. brevis PK08	Baechu kimchi (Napa cabbage)	Reduced tyramine content by 66.65%; successfully decreased histamine and putrescine; confirmed presence of the multicopper oxidase (MCO) gene for biogenic amine degradation.	[77]
L. brevis GDMCC 1.773	Carrot	Lowered transient nitrite peak accumulation to 11.88 mg/kg; achieved the highest sensory scores for quality, flavor, and texture among tested lactic acid bacteria.	[76]
L. brevis YSJ3 (CGMCC No. 23307)	Carrot juice (+sugar and MSG)	Significantly increased GABA and short-chain fatty acids; oral administration in in vivo models prolonged sleep duration, relieved anxiety, and beneficially modulated gut microbiota.	[74]
L. brevis CGMCC No. 28114	Northeastern sauerkraut	Reduced nitrite content to 0.14 mg/kg; inhibited spoilage bacteria; improved aroma, sourness, and visual gloss by increasing beneficial volatile compounds and reducing off-odors.	[78]
L. brevis AR123	Chinese pickle	Effectively degraded nitrite to 0.83 mg/kg within 72 h; exhibited high salt and nitrite tolerance; significantly enhanced overall sensory acceptability.	[7]
L. brevis PL6-1 (CGMCC19868)	Chinese radish paocai	Accelerated fermentation and improved texture (hardness, springiness); enriched flavor profile by increasing floral/sweet aroma compounds and reducing unpleasant pungent odors.	[79]

Table 5. Summary of L. brevis applications in vegetable fermentations.

Strain	Substrate/Matrix	Key Findings and Outcomes	References
L. brevis	Carrot juice (+pectin hydrolysate)	Produced high GABA concentrations (45,890 mg/L) with 4% pectin hydrolysate supplementation; enhanced total phenolic content, antioxidant activity, and organic acids.	[73]
L. brevis PK08	Baechu kimchi (Napa cabbage)	Reduced tyramine content by 66.65%; successfully decreased histamine and putrescine; confirmed presence of the multicopper oxidase (MCO) gene for biogenic amine degradation.	[77]
L. brevis GDMCC 1.773	Carrot	Lowered transient nitrite peak accumulation to 11.88 mg/kg; achieved the highest sensory scores for quality, flavor, and texture among tested lactic acid bacteria.	[76]
L. brevis YSJ3 (CGMCC No. 23307)	Carrot juice (+sugar and MSG)	Significantly increased GABA and short-chain fatty acids; oral administration in in vivo models prolonged sleep duration, relieved anxiety, and beneficially modulated gut microbiota.	[74]
L. brevis CGMCC No. 28114	Northeastern sauerkraut	Reduced nitrite content to 0.14 mg/kg; inhibited spoilage bacteria; improved aroma, sourness, and visual gloss by increasing beneficial volatile compounds and reducing off-odors.	[78]
L. brevis AR123	Chinese pickle	Effectively degraded nitrite to 0.83 mg/kg within 72 h; exhibited high salt and nitrite tolerance; significantly enhanced overall sensory acceptability.	[7]
L. brevis PL6-1 (CGMCC19868)	Chinese radish paocai	Accelerated fermentation and improved texture (hardness, springiness); enriched flavor profile by increasing floral/sweet aroma compounds and reducing unpleasant pungent odors.	[79]

7. Applications of L. brevis in Cereals and Bakery Products

7.1. Sourdough and Bakery Products

L. brevis has emerged as a versatile starter culture in bakery fermentation, with applications spanning traditional wheat sourdough, specialty breads, and gluten-free formulations. For example, its application in wheat flour-based bioingredients yields a robust and complex metabolite profile, including lactic, acetic, phenyllactic, and 4-hydroxy-phenyllactic acids [80]. The heterofermentative metabolism of this strain generates both lactic and acetic acids, with the latter contributing to enhanced antimicrobial activity and extended shelf life [15]. L. brevis ED25 in sourdough demonstrated synergistic effects, with the bacterium providing acidification (final pH 3.4 after 21 h at 30 °C), though the acidification rate of stored freeze-dried cultures was slower than fresh cultures during the first 9 h of fermentation [81]. The evolved strain L. brevis SPC 77-E3, developed through adaptive laboratory evolution for enhanced acid tolerance, maintained identical pH, total titratable acidity (TTA), and CO₂ production patterns to its parental strain SPC-SNU 70-2 in both sourdough and white pan bread, while producing higher abundances of volatile esters and acids in sourdough that contribute to fresh and sour taste profiles [82]. These findings underscore the importance of strain selection and culture management in optimizing L. brevis performance in diverse bakery applications.

The technological contributions of L. brevis in bakery fermentation extend beyond acidification and encompass multiple functional roles that directly impact dough rheology and bread quality. The Flora-Pan L-75 strain used as a 10% preferment in wheat dough lowered pH to 5.05–5.10 and increased TTA to 3.79–6.11 depending on flour type, significantly affecting dough development time and firmness while decreasing extensibility [83]. These rheological changes are likely driven mainly by fermentation acidification, which modifies gluten protein interactions and dough development. Furthermore, EPS-producing strains can significantly improve dough water retention, viscosity, crumb softness, and overall stability, although the specific EPS yields of L. brevis in these bakery systems remain critically underreported in the literature. The production of bioactive compounds has garnered increasing attention, particularly for GABA enrichment. L. brevis A7 in amaranth-wheat sourdough bread achieved GABA concentrations up to 39 mg/kg, demonstrating strain-specific glutamate decarboxylase activity [84]. Although phytase activity has been mentioned in several studies, it lacks comprehensive quantitative characterization in baked products, representing a notable research gap. The proteolytic activity of the strain contributes to dough extensibility and flavor development through peptide and amino acid release, with L. brevis AM7 producing antifungal peptides (ranging from 1240.7 to 2624.2 Da) during faba bean flour fermentation, which subsequently improved the shelf life of composite faba-wheat bread [85].

The quality and sensory effects of L. brevis fermentation reveal both advantages and challenges that merit critical evaluation. Texture improvements have been consistently reported, with L. brevis LMG P-25726 bioingredient enabling fiber-enriched wheat bran bread (20 g/100 g bran) to achieve specific volume and crumb softness comparable to bread without bran, effectively counteracting the typical negative effects of bran on bread structure [86]. Flora-Pan L-75 preferment significantly increased the specific volume and decreased the crumb hardness of wheat bread, with biological acidification proving more effective than chemical acidification with lactic acid [83]. However, black rice sourdough bread showed increased hardness and chewiness positively correlated with sourdough powder content (0–30%) and storage time, indicating that high inclusion rates may compromise texture in certain formulations [15]. Shelf-life extension through antifungal activity represents a major practical benefit, with L. brevis ITM18 bioingredient delaying Aspergillus niger growth by 1 d in pan bread and showing efficacy comparable to 0.3% calcium propionate, attributed to the synergistic effects of phenyllactic acids and proteinaceous compounds that remain thermally stable during baking [80]. Black rice sourdough bread with 30% sourdough powder delayed fungal growth by 2 days compared to controls, demonstrating dose-dependent antifungal effects [15]. However, while functional and shelf-life metrics often improve, the sensory outcomes can be highly variable. For instance, amaranth-wheat sourdough bread fermented with L. brevis A7 showed significantly lower general liking than the control bread despite enhanced GABA and phenolic content, indicating that nutritional improvements do not inherently translate to consumer acceptance [84]. Critical research gaps include limited comparative data on L. brevis performance versus other LAB species in identical bakery systems, insufficient mechanistic understanding of EPS structure-function relationships in dough, lack of standardized protocols for bioactive compound quantification across studies, and minimal investigation of L. brevis behavior in gluten-free matrices beyond pearl millet. Addressing this gap is essential, as the food industry currently faces significant challenges in formulating high-quality gluten-free bakery products from sustainable alternative crops such as maize, sorghum, and chickpeas [87]. The efficacy of L. brevis bioingredients was notably reduced in bran-containing formulations, with significant antimicrobial effects in white wheat bread but non-significant effects in wheat bran bread, suggesting a matrix-dependent performance that requires further investigation [86]. Additionally, the slower acidification kinetics of freeze-dried cultures compared to fresh cultures raises practical concerns for industrial applications, where consistent fermentation rates are essential for process control [81].

7.2. Other Cereal-Based Foods

L. brevis has demonstrated significant technological and functional versatility in cereal fermentation applications, ranging from traditional grain beverages to specialized functional ingredients. Single-culture applications have predominantly focused on GABA biosynthesis and grain modification, with strain-specific performance variations that reflect distinct metabolic capabilities. Rice-based fermentations have emerged as the most extensively studied cereal substrates, with L. brevis BJ20 achieving 87.9% GABA content of total free amino acids in fermented rice germ extract under optimized conditions (8% monosodium glutamate, 72 h at 37 °C), representing an 80% glutamate-to-GABA conversion efficiency [88]. Similarly, L. brevis VTCC-B397 fermentation of defatted rice bran extract yielded 7.69 g/L GABA at pH 5.12 and 34 °C with 0.56 M MSG supplementation, a 51.3-fold increase compared to unfermented rice bran (0.15 g/L) and a 23-fold enhancement over unoptimized fermentation conditions. These rice-based applications demonstrate the critical influence of pH control on GABA biosynthesis, with pH 5.0 maintaining optimal glutamate decarboxylase activity while preventing post-fermentation GABA degradation [89]. Barley malt applications have revealed distinct technological roles, with L. brevis R2Δ reducing malting losses by 31.8% (from 10.81% to 7.37%) while simultaneously increasing the extract yield by 3.1% through acidification-mediated rootlet growth inhibition and microbial modulation. Fermented wort treatment achieved 71.0 mmol/L titratable acidity, reduced Fusarium spp. contamination by >90%, and eliminated deoxynivalenol-3-glucoside mycotoxin to below the detection limit, demonstrating dual functionality in both process optimization and food safety enhancement. Importantly, comparisons between live cells and pasteurized ferments indicate that the metabolic products of L. brevis (such as organic acids, cyclic dipeptides, and phenolic compounds) contribute more significantly to these technological outcomes than the presence of viable cells [90]. Sorghum flour modification by L. brevis at 0.20% inoculation for 12 h resulted in the acidification-driven activation of endogenous grain enzymes. This facilitated the proteolytic and amylolytic degradation of starch granules, increasing the whiteness values and protein content, while reducing tannin levels by 31–35% and lowering the bulk density through structural compaction [91].

Co-culture applications of L. brevis in cereal fermentation remain significantly underrepresented in the literature, and systematic evaluations comparing its performance with that of other heterofermentative or homofermentative LAB species are notably absent. The absence of robust co-culture data represents a critical knowledge gap, particularly given the potential synergistic effects observed in dairy and vegetable fermentations where L. brevis co-cultures with L. plantarum or P. pentosaceus species have shown enhanced bioactive compound production and sensory profile improvements. Future research should prioritize systematic co-culture evaluations in cereal matrices by examining strain compatibility, metabolic interactions, and comparative performance metrics across diverse grain substrates to establish evidence-based starter culture formulations for cereal fermentation applications.

8. Conclusions

L. brevis has established itself as a highly versatile and valuable starter culture across diverse food fermentation sectors. Its robust environmental adaptability, particularly its halotolerance and ability to thrive in complex, nutrient-limited matrices, makes it a powerful biological tool for developing functional foods and valorizing agricultural by-products. This species is exceptional in its capacity to synthesize bioactive metabolites, most notably GABA, and produce exopolysaccharides that improve product rheology and viability during gastrointestinal transit. Furthermore, its intrinsic ability to degrade toxic compounds, such as nitrites and biogenic amines, significantly enhances the safety and bioprotective profiles of fermented meat, seafood, and vegetables. Despite these profound functional advantages, the broader industrial application of L. brevis is frequently limited by strain-specific technological constraints. In matrices such as dairy and certain plant-based systems, its inherently weak proteolytic activity and slow acidification kinetics generally necessitate its use in synergistic co-culture systems with traditional starter cultures. While co-culturing successfully overcomes these barriers and often leads to enhanced texture, flavor complexity, and bioactive yields, a persistent challenge remains in the delicate trade-off between maximizing functional benefits and maintaining optimal sensory quality. Conditions that favor high GABA accumulation or extended shelf life can sometimes result in excessive acidity or undesirable flavor profiles that negatively impact consumer acceptance. To fully unlock the biotechnological potential of L. brevis, future research must bridge the gap between controlled laboratory studies and real-world challenges. Priorities should include the integration of multi-omics approaches, specifically comparative genomics and transcriptomics, to elucidate strain-specific metabolic networks, identify genes associated with targeted functional traits, and accelerate rational strain selection. Systematic comparative evaluations of co-culture dynamics and targeted strain evolution are also critical for improving technological robustness. By addressing these research gaps, L. brevis can be more precisely integrated into industrial fermentation, fulfilling the growing global demand for clean-label, health-promoting, and sustainably produced next-generation foods.