Search Results (1,795)

The viable bacterial count is a crucial quality indicator for lactic acid bacteria (LAB) starters and fermented foods. Metabolic activity is an integral component of stress tolerance pathways. Lacticaseibacillus rhamnosus exhibits enhanced heat and oxidative stress tolerance in tryptone-free media. To investigate the stress tolerance mechanisms from a metabolic perspective, the heat and oxidative stress tolerance and transcriptomic changes in L. rhamnosus hsryfm 1301 and its ccpA deficient strain (ΔccpA) were analyzed under different nitrogen source conditions. Slower growth, decreased heat stress tolerance, and enhanced oxidative stress tolerance were observed in ΔccpA in MRS. Compared to the wild-type strain, 260 genes were upregulated and 55 genes were downregulated in ΔccpA, mainly including carbon source transport and metabolism genes, but no typical stress tolerance genes. The regulation of pfk, pyk, dnaK, and groEL was different from that in other lactic acid bacteria. The pathways related to acetate production were regulated solely by ccpA deletion, while dnaK, groEL, and de novo pyrimidine synthesis genes were only regulated by tryptone. Fatty acid and purine synthesis genes and glmS were co-regulated by ccpA and tryptone. The deletion of ccpA eliminated the nitrogen source-induced oxidative stress tolerance changes. It was found that ccpA in L. rhamnosus can affect both carbon and nitrogen source metabolism, altering stress tolerance. Full article

This study investigated the combined effects of lactic acid bacteria (LAB) fermentation and different milling methods (wet, semi-dry, and dry) on the physicochemical properties of glutinous rice flour (GRF) and the texture of the final product. A systematic analysis of rice samples treated with three LAB strains (Lactiplantibacillus plantarum CGMCC 1.12974, Limosilactobacillus fermentum CICC 22704, and Lactobacillus acidophilus CICC 22162) revealed that fermentation pretreatment created favorable conditions for subsequent physical milling by degrading the protein network and modifying the starch structure. The results demonstrated that fermentation combined with dry or semi-dry milling significantly improved the whiteness of GRF and the contents of γ-aminobutyric acid (GABA), total phenols, and total flavonoids, while reducing the contents of damaged starch (except in samples fermented with Lb. acidophilus) and protein by 2.91–12.43% and 17.80–32.09%, respectively. The functional properties of the GRF were also optimized: fermented flour exhibited higher peak viscosity, lower gelatinization temperature, and higher gelatinization enthalpy. Texture profile analysis revealed that glutinous dumplings prepared from fermented dry/semi-dry milled GRF, particularly those fermented with Lp. plantarum, showed significantly reduced hardness and chewiness, along with significantly improved cohesiveness and resilience. Consequently, their texture approximated that of high-standard wet-milled products. Correlation analysis based on the top ten discriminative features selected by random forest identified peak viscosity and breakdown viscosity as the most important positive factors associated with superior texture (high resilience, high cohesiveness, and low hardness), whereas damaged starch content and protein content were key negative correlates. In summary, this study confirms that the combination of fermentation and milling exerts a beneficial influence on the functional quality of GRF. Full article

Fructophilic lactic acid bacteria (FLAB), Apilactobacillus kunkeei strains AG8 and AG9 were selected in the current study for in-depth analysis. Cultivation on fructose yeast peptone (FYP) medium with varying fructose concentrations (1%, 10%, and 30%) revealed that higher fructose levels promoted acetate production over lactate, confirming a heterofermentative metabolic profile. Ethanol production was negligible, consistent with the absence of alcohol dehydrogenase (ADH) activity. Enzyme assays showed fructokinase activity doubled at 30% fructose, while acetate kinase activity increased and L-lactate dehydrogenase activity decreased. This shift in enzyme ratios from 1:1 at 1% fructose to 10:1 or 15:1 at higher concentrations explains the metabolic preference for acetate. Apb. kunkeei is an obligate FLAB, growing poorly on glucose unless supplemented with external electron acceptors like pyruvate or oxygen. It lacks ADH, but retains acetaldehyde dehydrogenase (ALDH), enabling acetate production and additional ATP generation, enhancing biomass yield. The absence of the adhE gene contributes to NAD+/NADH imbalance and favors acetate production. Gene expression studies targeting fructose transport enzymes showed elevated expression of ABC transporters and carbohydrate metabolism genes in response to fructose. ADH expression remained low across sugar concentrations. Fructokinase gene expression was shown to be strain specific. Neither strain expressed the ABC transporter ATP-binding protein gene on glucose, nor the bacteriocin ABC transporter gene, correlating with the absence of antibacterial activity. These findings underscore the metabolic specialization of Apb. kunkeei, its reliance on fructose, and the role of ABC transporters in optimizing fermentation. The strain-specific gene expression and metabolic flexibility highlight its potential as a probiotic and feed additive in apiculture and biotechnology. Full article

Background: Qu was the core starter of traditional Chinese fermentation and had long relied on artisan experience, which led to limited batch stability and standardization. This review organized the preparation processes, microbial diversity, and application patterns of qu in foods from experience to science perspective. Methods: This work summarized typical process parameters for daqu, xiaoqu, hongqu, wheat bran or jiangqu, douchi qu, and qu for mold curd blocks used for furu. Parameters covered raw material moisture, bed thickness, aeration or turning, drying, final moisture, and classification by peak temperature. Multi-omics evidence was used to analyze the coupling of temperature regime, community assembly, and functional differentiation. Indicators for pigment or enzyme production efficiency and safety control such as citrinin in hongqu were included. Results: Daqu showed low, medium, and high temperature regimes. Thermal history governed differences in communities and enzyme profiles and determined downstream fermentation fitness. Xiaoqu rapidly established a three-stage symbiotic network of Rhizopus, Saccharomyces, and lactic acid bacteria, which supported integrated saccharification and alcohol fermentation. Hongqu centered on Monascus and achieved coordinated pigment and aroma formation with toxin risk control through programmed control of temperature, humidity, and final moisture. Wheat bran or jiangqu served as an enzyme production engine for salt-tolerant fermentation, and the combined effects of heat and humidity during the qu period, aeration, and bed loading determined hydrolysis efficiency in salt. Douchi and furu mold curd blocks used thin-layer cultivation and near-saturated humidity to achieve stable mold growth and reproducible interfacial moisture. Conclusions: Parameterizing and online monitoring of key variables in qu making built a process fingerprint with peak temperature, heating rate, and moisture rebound curve at its core. Standardization and functional customization guided by temperature regime, community, and function were the key path for the transition of qu from workshop practice to industry and from experience to science. This approach provided replicable solutions for flavor consistency and safety in alcoholic beverages, sauces, vinegars, and soybean products. Full article

This review indicates that microalgae may serve as a sustainable supply of bioactive compounds and lipids over the long run. It also discusses the significance of lactic acid bacteria (LAB) and Saccharomyces cerevisiae in biotransformation processes. Microalgae contribute to food security and environmental sustainability due to their rapid growth and diverse applications, including food, feed, and biofuels. Fermentation with LAB and S. cerevisiae enhances the nutritional and functional properties of microalgal biomass, rendering it more digestible, bioactive, and palatable. This review discusses the metabolic characteristics of LAB and S. cerevisiae, their ability to modify microalgal components through enzymatic action, and the resultant products, including enhanced fatty acid profiles and bioactive compounds. Furthermore, the biotransformation of pigments during LAB fermentation is examined, revealing significant alterations in the hue and bioactivity of the pigments, hence enhancing the appeal of microalgal products. Future perspectives emphasize the necessity for further investigation to identify optimal fermentation conditions and to explore the synergistic interactions between LAB and S. cerevisiae in the production of novel beneficial components from microalgae using both microbes. Full article

Milk represents not only a source of essential nutrients but also a versatile matrix for the development of functional foods when combined with lactic acid bacteria (LAB) fermentation. While cow milk is the most widely consumed, alternative matrices such as goat and donkey milk possess distinctive compositional features that may influence the bioactivity of fermented products. In this work, fifteen different strains belonging to LAB and bifidobacteria were initially tested for their ability to ferment cow, goat, and donkey milk. Fermented samples showing the best acidification rate were further screened for total phenolic content (TPC), radical scavenging activity (RSA), and effects in human colon epithelial cells and Caco-2 adenocarcinoma cells. The results showed that fermentation modulated TPC in a strain- and matrix-dependent manner, with donkey milk showing the most consistent increases. RSA was significantly enhanced in fermented samples, particularly those inoculated with Lacticaseibacillus casei BGP93 and LC4P1 strains and Limosilactobacillus reuteri ATCC23272. Cell viability assays confirmed the absence of cytotoxicity, and fermented milk extracts reduced ROS under induced oxidative stress. Antimicrobial assay showed that Lactiplantibacillus plantarum LPAL selectively inhibited Listeria monocytogenes, with the strongest effect observed in donkey milk. These findings suggest that LAB-fermented milks from goats and donkeys may represent safe functional foods with improved antioxidant and antimicrobial activities. Full article

The aim of the study was to determine the effect of Swiss chard powder (SCP) as a natural nitrite source on the volatile compounds and other qualitative properties of heat-treated sucuk (HTS). Three formulations were created for the production of HTS: control (no nitrite addition), synthetic nitrite (SN, 150 mg/kg NaNO₂ addition), and natural nitrite from Swiss chard powder (SCPN) (SCP equivalent to 150 mg/kg NaNO₂). The HTS production was carried out under controlled conditions. Physicochemical and microbiological properties of the HTS were investigated during the production stages. The final product was analyzed for volatile compounds, residual nitrite, and sensory properties. A higher mean pH value was found in the SCPN group in comparison with other groups (p < 0.05). In all production stages, the lowest a_w values were observed in the presence of SCPN (p < 0.05). The highest mean L* value was determined in the group with SN (p < 0.05). Groups containing SN or SCPN exhibited higher a* values compared to the control during fermentation, heat treatment, and drying. The SN group had the lowest TBARS value during all these stages (p < 0.05). There was no significant difference in the amount of residual nitrite between the SCPN and SN groups (p > 0.05). In terms of sensory parameters, nitrite groups (SCPN and SN) had higher values than the control group (p < 0.05). Lactic acid bacteria exhibited good growth during fermentation in all groups. Although SCP positively affected many volatile compounds, this effect was not strong enough to alter the sensory properties of the product. Correlation analysis of volatile compounds revealed that the control group was significantly different from the groups using SN or SCPN. Additionally, similar characteristics in volatile compounds and sensory attributes were observed in the SN and SCPN groups. As a result, characteristics of the final products were not usually adversely affected by the use of SCP in HTS production. Full article

This study investigated the effects of three different lactic acid bacteria (LAB) strains (Limosilactobacillus fermentum 14, Limosilactobacillus reuteri 18, and Lactiplantibacillus plantarum CAU808) on the nutrient components, bioactivity, and flavor profiles of a medicinal and edible homologous (MEH) plant-based beverage (QJ). Results demonstrated that QJ served as an excellent substrate for LAB growth, with viable counts of all three LAB exceeding 8.5 log CFU/mL after fermentation. Fermentation significantly reduced soluble sugar contents while increasing organic acids levels. A slight enhancement in ABTS radical scavenging capacity was also observed. Electronic tongue (E-tongue) analysis revealed that LAB fermentation markedly decreased bitterness and enhanced sourness, sweetness, and umami, thereby improving the overall taste profile. Furthermore, electronic nose (E-nose) and HS-SPME-GC-MS analyses indicated distinct alterations in odor characteristics post-fermentation. A total of 87 volatile compounds were identified, with alcohols constituting the predominant group. Compared to the other two strains, Lactiplantibacillus plantarum CAU808 demonstrated superior fermentation performance and more favorable flavor characteristics. These findings provide a theoretical basis for utilizing LAB fermentation to optimize the flavor of MEH plant-based beverages. Full article

Fermented sausages are popular worldwide due to their sensory and nutritional characteristics, as well as their convenience for storage and consumption. The production and consumption of meat products are associated with negative impacts from the risks of high sodium intake, such as cardiovascular disease and hypertension. Salt (NaCl) plays an important role in the preservation, water loss during drying, reduction in water activity, and sensory characteristics of meat and other fermented food products. NaCl reduction is considered a challenge because it affects the sensory properties of meat and can compromise the safety and microbiological parameters related to the spoilage of the fermented meat product. The use of microorganisms, such as LAB, has been studied as an innovative way to substitute traditional preservatives. They produce various metabolites, including bioactive and antimicrobial substances that are actively involved in health benefits and guarantee the safety of meat products. These natural substances produced by bacteria extend shelf life by inhibiting spoilage and pathogenic microorganisms. This review discusses the potential application of lactic acid bacteria in the reformulation of fermented sausages, challenges, and beneficial effects on sensorial, safety, and health properties. Full article

This research evaluated the influence of lactic acid bacteria and cellulase, individually or in combination, on the quality of mixed amaranth and sweet potato vine silages. The experiment included four groups: control group with no additives addition (CG), added cellulase group (AS1), added lactic acid bacteria group (AS2) and combined supplementation group (AS3), with five replicates per group. The ensiling period lasted for 60 days. Parameters of silage, including chemical components, fermentation profile, aerobic stability, and in vitro nutrient digestibility, were determined. The results revealed that the quality of amaranth and sweet potato vine mixed silage was improved to a certain degree after addition of two additives individually. Combining these additives observably increased (p < 0.05) the lactic acid and crude protein contents and decreased the pH, ratio of ammonia nitrogen to total nitrogen and neutral detergent fiber content of mixed silage. Compared with the CG and AS1 groups, the number of lactic acid bacteria in the AS3 group increased significantly (p < 0.05), while aerobic bacteria and mold counts showed the opposite tendency. Also, the in vitro dry matter, crude protein and neutral detergent fiber digestibility of the AS3 group were higher (p < 0.05) than those of the CG group. Combined inoculation observably reduced (p < 0.05) the ammonia nitrogen concentration and increased (p < 0.05) the propionic and butyric acid concentrations of mixed silage under in vitro incubation. In summary, the inoculation of lactic acid bacteria and cellulase can enhance the fermentation profile and nutritional values of mixed silage made from amaranth and sweet potato vine, and the best improvement effects are obtained by the combined utilization of the two additives. Full article

This study deals with the influence of various oenological preparations on malolactic fermentation. The influence of chitosan, fumaric acid, a tannin-based (Estaan) oenological preparation and medium-chain fatty acids (MCFAs) was investigated, along with a new preparation based on a combination of selected hydroxycinnamic acids and MCFAs. Growth curves were obtained using Oenococcus oeni, Lactobacillus brevis and Lactobacillus plantarum bacteria. Experimental work was also carried out on microsamples of wine, where individual inhibitors were added to wine inoculated with O. oeni culture and an HPLC analysis was performed to measure malic acid levels. Fumaric acid had the strongest inhibitory effect on L. plantarum at a dose of 2.5 g∙L⁻¹, while chitosan had the strongest effect on O. oeni at a dose of 2.5 mg∙L⁻¹. P-coumaric acid in combination with MCFAs (0.4 g∙L⁻¹ of p-coumaric acid + 10 mg∙L⁻¹ MCFAs) and Mix (0.4 g∙L⁻¹ of p-coumaric acid + 0.4 g∙L⁻¹ of ferulic acid + 10 mg∙L⁻¹ MCFA) had the strongest inhibitory effects on O. oeni and L. brevis. Finally, MCFAs had the strongest inhibitory effect on L. brevis at a dose of 1000 mg∙L⁻¹, and Estaan had the strongest effect on L. plantarum at a dose of 25 g∙L⁻¹. Full article

This study aimed to investigate the effects of Levilactobacillus brevis, Lacticaseibacillus paracasei, and Lacticaseibacillus rhamnosus strains isolated from Mihalic cheese, also known as “weeping cheese”, on fermentation kinetics, microbial viability, and textural and aromatic properties of the butter matrix. The effects of the isolates were determined on acidification kinetics (V_max, T_vmax, pH_vmax), viability proportion index (VPI), textural parameters (firmness, work of shear, stickiness, work of adhesion), and volatile aroma compounds (GC-MS) formation. This study found that the BLR sample containing Lacticaseibacillus rhamnosus maintained its limited viability under acidic stress conditions despite its high fermentation rate and low pH_vmax values. The BLP sample containing Lacticaseibacillus paracasei exhibited high viability due to its low acidification rate and limited pH change. Determining the chemical classes to which the aroma compounds in the BLP sample belonged revealed a composition rich in fatty acids. The BLB sample containing Levilactobacillus brevis produced a high ΔpH value and an aroma profile rich in aldehyde compounds. Examination of the macro-structural properties of the butter samples revealed that the sample containing Lacticaseibacillus rhamnosus, similar to the control sample (BMC), was more compact and rigid during storage. In contrast, samples containing Lacticaseibacillus paracasei and Levilactobacillus brevis had a softer/spreadable texture. These findings demonstrate the potential of lactic acid bacteria isolates from the traditional Mihalic cheese microbiota as biological catalysts for the development/improvement of texture, aroma, and sensory quality in high-fat dairy products and for the industrial production of products modified to meet consumer preferences. Full article

The animal husbandry industry is a major source of agricultural greenhouse gas emissions, and methods to reduce methane production from livestock during rumen fermentation are an important research issue. Distillery spent wash (DSW) is a by-product of the brewing industry, and to our knowledge, its application in feed processing has rarely been reported. This work investigated the effect of using DSW as an additive on silage fermentation and in vitro methane production. A small-scale silage production system for whole-plant maize was applied, and maize was treated without (control) and with DSW (G2, 10 mL·kg⁻¹ fresh matter (FM); G4, 20 mL·kg⁻¹ fresh matter). After 60 days of ensiling, the pH value of G2- and G4-treated whole-plant maize was reduced (p < 0.05), while lactic acid production was significantly enhanced to 3.40% DM for G2 and to 3.43% DM for G4, effectively improving silage fermentation. In fact, the addition of DSW shifted the bacterial community structure in whole-plant maize silage, significantly increasing the dominance of Lactiplantibacillus from 10.1% (CK) to 74.1% (G2) and 62.5% (G4) and thereby decreasing the diversity indices of silage samples. However, DSW application increased the ammonia-N levels in silage by 135.29–147.06% compared with the control. Importantly, there was a reduction of 0.70 and 0.55 percentage units in CK for G2 and G4, respectively, which represent 57.6% and 44.0% reductions in the acetic acid concentration, respectively, which were accompanied by a trend of decreasing methane production and Methanobrevibacter abundance. In conclusion, DSW exhibits potential for enhancing lactic acid fermentation by increasing Lactiplantibacillus and for inhibiting in vitro rumen methane production by promoting Methanobrevibacter dominance. Full article

Sant’Agostino green table olives, traditionally processed in Apulia and flavoured with Foeniculum vulgare, represent a niche product whose microbial ecology remains largely unexplored. This study aimed to characterise the microbiota of the final product (both brine and fruit) after six months of storage with wild fennel. Four production batches were analysed using a combined culture-dependent and culture-independent approach. Microbiological counts revealed variable levels of aerobic mesophilic microorganisms, yeasts, lactic acid bacteria (LAB), and staphylococci, with yeasts and LAB being predominant. Ten LAB strains were identified, including Enterococcus faecium, Leuconostoc mesenteroides subsp. jonggajibkimchii, Leuconostoc mesenteroides subsp. cremoris, Leuconostoc pseudomesenteroides, Lactiplantibacillus plantarum, and Lactiplantibacillus pentosus. Yeast isolates belonged to Candida tropicalis, Torulaspora delbrueckii, and Saccharomyces cerevisiae. Amplicon sequencing (MiSeq Illumina) revealed distinct bacterial profiles between fruit and brine samples, with taxa from Actinobacteria, Bacteroidetes, Enterococcus, Lactobacillus, Leuconostoc, Alphaproteobacteria, Enterobacteriaceae, and other Gammaproteobacteria. Enterococcus and Leuconostoc were consistently detected, while Lactobacillus sensu lato appeared only in one fruit and one brine sample. These findings provide new insights into the microbial diversity of Sant’Agostino olives and contribute to the understanding of their fermentation ecology and potential for quality and safety enhancement. Full article

Background/Objectives: Within the spectrum of lactic acid bacteria, Lacticaseibacillus casei and Lactobacillus johnsonii are of particular technological and nutritional significance. Protein fortification of fermented dairy systems offers dual benefits: it improves product quality while enhancing probiotic resilience. Supplementary proteins supply bioavailable nitrogen and peptides that stimulate bacterial metabolism and contribute to a viscoelastic gel matrix that buffers cells against gastric acidity and bile salts. The aim of this study was to clarify the functional potential of such formulations by assessing probiotic survival under in vitro digestion simulating oral, gastric, and intestinal phases. Methods: Sheep milk was fermented with L. casei 431 or L. johnsonii LJ in the presence of whey protein isolate (WPI), soy protein isolate (SPI), or pea protein isolate (PPI) at concentrations of 1.5% and 3.0%. Physicochemical parameters (pH, titratable acidity, color, syneresis), organoleptic properties, and microbiological counts were evaluated. The viability of L. casei and L. johnsonii was determined at each digestion stage, and probiotic survival rates were calculated. Results: Samples with L. johnsonii consistently exhibited lower pH values compared to L. casei. Across both bacterial strains, the addition of 1.5% protein isolate more effectively limited syneresis than 3.0%, regardless of protein type. Samples fortified with WPI at 1.5% (JW1.5) and 3.0% (JW3.0) were rated highest by the panel, demonstrating smooth, homogeneous textures without grittiness. The greatest bacterial survival (>70%) was observed in WPI-fortified samples (JW1.5, JW3.0) and in SPI-fortified JS3. Conclusions: Protein isolates of diverse origins are suitable for the enrichment of fermented sheep milk, with 1.5% supplementation proving optimal. Such formulations maintained desirable fermentation dynamics and, in most cases, significantly improved the survival of L. casei and L. johnsonii under simulated gastrointestinal conditions, underscoring their potential in the development of functional probiotic dairy products. Full article