Search Results (363)

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the vertebrate central nervous system, known for its role in promoting sleep, reducing anxiety, regulating blood pressure, and modulating stress, cognition, and behavior. Microbial fermentation offers an effective method for GABA production, with certain lactic acid bacteria (LAB) strains recognized as efficient producers. This study assessed the GABA-producing potential of 31 LAB strains, including isolates from traditional Bulgarian foods and plants. The strains were cultivated in an MRS medium supplemented with 1% monosodium glutamate (MSG), and GABA production was quantified using HPLC after derivatization with dansyl chloride. Most strains produced between 200 and 300 mg/L of GABA. However, Levilactobacillus brevis NCTC 13768 showed much higher productivity, reaching 3830.7 mg/L. To further evaluate its capacity, L. brevis NCTC 13768 was cultivated for 168 h in MRS medium with and without MSG. Without MSG, GABA production peaked at 371.0 mg/L during the late exponential phase. In contrast with MSG, GABA levels steadily increased, reaching 3333.6 mg/L after 168 h. RT-qPCR analyses of the glutamic acid decarboxylase (GAD) system showed that the genes of glutamate decarboxylase (gadB), glutamate-GABA antiporter (gadC), and transcriptional regulator (gadR) are significantly overexpressed when the culture reaches the late stationary phase of growth (96 h after the beginning of cultivation). These results identify L. brevis NCTC 13768 as a high-yield GABA producer, with potential applications in the production of fermented functional foods and beverages. Full article

In order to develop a new environmentally friendly microbial herbicide for the field of weed control, this study used the metabolite butyl hydroxybenzoate (BP) of the HY-02 strain of Alternaria as the research object. The BP emulsion formula was determined to be a mixture of BP, methanol, and Tween-20 in a ratio of 1:1:2 g/mL. The seed germination inhibition effect, the phytotoxicity of living plants, crop safety, and the field effect of the emulsion were studied. Research has found that adding 0.75% BP emulsion to the seed culture medium inhibits the germination of weed seeds such as Amaranthus retroflexus L., Malva verticillata L. var., and Chenopodium album L. While Brassica campestris L. seeds were unaffected, Triticum aestivum L and Hordeum vulgare L. stem and leaf growth were inhibited. Cucumis sativus L., Lactuca sativa L. var. asparagina, Spinacia oleracea L., and Capsicum annuum L. seeds are significantly inhibited, with germination rates below 20%. We sprayed 0.75% BP emulsion onto live potted plants; among the weeds, the incidence of Amaranthus retroflexus L., Lepyrodiclis holosteoides, Thlaspi arvense L, Galium spurium L., Malva verticillata L. var. Crispa, Chenopodium album L., and Avena fatua L reached 100%. The Pisum sativum L. and Triticum aestivum L. crops were not affected (NS), and they had slight plant height inhibition and slight susceptibility (LS) to highland Hordeum vulgare L. and peppers. They were highly phytotoxicity to Cucumis sativus L. and Spinacia oleracea L. Some plant leaves became infected and died, with incidences of 85% and 82%, respectively. The field experiment showed that after diluting the BP emulsifiable concentrate, the seedling stage spray was inoculated into the Triticum aestivum L. field, and it was found that the BP emulsifiable concentrate at the concentration of 1.00%~0.75% had a herbicidal effect on weeds such as Chenopodium album L., Elsholtzia densa Benth, and Amaranthus retroflexus L. in the Triticum aestivum L. field, and it was safe for Triticum aestivum L. crops in the field. These results indicate that BP emulsion could be developed into a new environmentally friendly microbial herbicide for field application in grass (Triticum aestivum L. and Hordeum vulgare L.) crops. At the same time, BP’s excellent antibacterial, low-toxicity, hydrolysis, and other effects can promote diversification in herbicide development. Full article

Microalgae are promising candidates for renewable biofuel production and nutrient-rich animal feed. Cultivating microalgae using wastewater can lower production costs but often results in biomass contamination and increases downstream processing requirements. This study presents a novel system that integrates an algae cultivator (AC) with a single-chamber microbial fuel cell (MFC) equipped with photosynthetic and air-cathode functionalities, separated by a ceramic membrane. The system enables the generation of electricity and production of clean microalgae biomass concurrently, in both light and dark conditions, utilizing wastewater as a nutrient source and renewable energy. The MFC chamber was filled with simulated potato processing wastewater, while the AC chamber contained microalgae Chlorella vulgaris in a growth medium. The ceramic membrane allowed nutrient diffusion while preventing direct contact between algae and wastewater. This design effectively supported algal growth and produced uncontaminated, harvestable biomass. At the same time, larger particulates and undesirable substances were retained in the MFC. The system can be operated with synergy between the MFC and AC systems, reducing operational and pretreatment costs. Overall, this hybrid design highlights a sustainable pathway for integrating electricity generation, nutrient recovery, and algae-based biofuel feedstock production, with improved economic feasibility due to high-quality biomass cultivation and the ability to operate continuously under variable lighting conditions. Full article

This study aimed to develop a sustainable bioinput using Streptomyces sp. BEI-18A cultivated in an alternative culture medium (ACM) formulated with winery spent yeast and composting leachate. Actinomycetes were initially isolated from grape waste composting piles and screened for agricultural potential in vitro. Streptomyces sp. BEI-18A was selected for further bioinput development based on its high siderophore production. The ACM formulation was optimized in three steps: (I) determining the optimal concentration of winery spent yeast through mixture design; (II) assessing the effect of composting leachate addition on microbial growth; and (III) establishing the final composition of ACM components. The optimized ACM consisted of 3 g/L spent yeast, 2 g/L sucrose, 1 g/L soybean extract, and 10% (v/v) composting leachate. Cultivation of Streptomyces sp. BEI-18A in this medium resulted in a bioinput containing 7.80 × 10⁷ CFU/mL. Its agricultural potential was validated in pot experiments with wheat and soybean, where application of the bioinput promoted significant improvements in early plant growth, enhancing several phytometric parameters. The results highlight the feasibility of valorizing agro-industrial residues as low-cost substrates for microbial bioinput production. This approach represents a promising strategy to foster sustainability in agriculture while reducing environmental impacts. Full article

Better understanding of the fitness and flexibility of microbial platform organisms is central to biotechnological process development. Live-cell experiments uncover the phenotypic heterogeneity of living cells, emerging even within isogenic cell populations. However, how this observed heterogeneity in growth relates to the variability of intracellular processes that drive cell growth and division is less understood. We here approach the question, how the observed phenotypic variability in single-cell growth rates links to metabolic processes, specifically intracellular reaction rates (fluxes). To approach this question, we employ the Maximum Entropy (MaxEnt) principle that allows us to bring together the phenotypic solution space, derived from metabolic network models, to single-cell growth rates observed in live-cell experiments. We apply the computational machinery to first-of-its-kind data of the microorganism Corynebacterium glutamicum, grown on different substrates under continuous medium supply. We compare the MaxEnt-based estimates of metabolic fluxes with estimates obtained by assuming that the average cell operates at its maximum growth rate, which is the current predominant practice in biotechnology. Full article

This study evaluates the impact of biotic elicitors and hormone regimes on the in vitro establishment, shoot multiplication, and organogenesis of Solanum tuberosum L. cv. Fianna under controlled laboratory conditions. Explants derived from pre-treated tubers were cultured on Murashige and Skoog (MS) medium supplemented with vitamins and varying concentrations of growth regulators or elicitors. Aseptic establishment achieved a high success rate (~95%) using a 6% sodium hypochlorite disinfection protocol. Multiplication was significantly enhanced with a combination of 0.2 mg L⁻¹ naphthaleneacetic acid (NAA) and 0.5–1.0 mg L⁻¹ benzylaminopurine (BAP), producing the greatest number and length of shoots and roots. Direct organogenesis was stimulated by bio-elicitors Activane^®, Micobiol^®, and Stemicol^® in (MS) basal medium at mid-level concentrations (0.5 g or mL L⁻¹), improving shoot number, elongation, and root development. Activane^®, Micobiol^®, and Stemicol^® are commercial elicitors that stimulate plant defense pathways and morphogenesis through salicylic acid, microbial, and jasmonic acid signaling mechanisms, respectively. Indirect organogenesis showed significantly higher callus proliferation in Stemicol^® and Micobiol^® treatments compared to the control medium, resulting in the highest fresh weight, diameter, and friability of callus. The results demonstrate the potential of biotic elicitors as alternatives or enhancers to traditional plant growth regulators in potato tissue culture, supporting more efficient and cost-effective micropropagation strategies. Full article

Organic-waste-derived volatile fatty acids (VFAs) are promising substrates for fungal biomass cultivation, offering a nutrient-rich medium capable of meeting microbial growth requirements. However, the growth and biomass productivity are highly influenced by the VFAs’ composition and mode of operation. This study investigated the cultivation of Aspergillus oryzae fungal biomass using agro-industrial-derived VFA effluent, employing repeated-batch and fed-batch (stepwise and continuous-feeding) cultivation modes to evaluate fungal growth and biomass composition. The highest dry biomass yield of 0.41 dry biomass/gVFAs_fed (g/g) was achieved in fed-batch mode with continuous feeding, where the biomass exhibited pellet morphology, facilitating ease of harvesting. The crude protein content varied according to the cultivation strategy, reaching 45–53% in continuous-feeding fed-batch mode, while it was 34–42% in stepwise fed-batch mode. Additionally, the fungal biomass contained significant levels of essential macronutrients and trace elements, including Mg, Ca, K, Mn, and Fe, which are crucial if the biomass is intended to be used in animal feed formulations. This study highlights the effects of cultivation modes on biomass composition and the potential of VFA-derived fungal biomass as a sustainable feed ingredient. Full article

The increasing interest in natural preservatives has driven the search for effective microbial agents capable of controlling spoilage molds in cured meat products. In this study, the efficacy of Debaryomyces hansenii strains as biocontrol agents against spoilage molds in dry-cured meat products was evaluated through a dual experimental approach using both synthetic (PDA) and meat-derived media (LBM). While all D. hansenii strains demonstrated strong antifungal activity in nutrient-rich synthetic media, their performance in meat-like conditions was moderate to high, with significant differences depending on the mold species, the yeast strain, and their interaction with the culture medium. Our results highlight that antifungal efficacy is strongly influenced by the growth environment, underscoring the limitations of traditional in vitro assays that depend solely on synthetic media. Incorporating food-mimicking systems early in the screening process proved critical to identify strain–mold–medium combinations with the highest potential. These findings support the potential application of native D. hansenii strains as natural preservatives to enhance the safety and shelf life of dry-cured meats, emphasizing the importance of testing in conditions that closely resemble the target food environment to select the most effective biocontrol solutions. Full article

An emerging area of microbial biology focuses on oligonucleotides excised from functional RNAs and subsequently fulfilling an independent cellular role. Some of these products are subjected to modifications that may expand their functional inventory. Here, we applied a differential analysis of intra- and extracellular RNA fragments produced by wild-type Escherichia coli and its dps-null mutant and discovered leucine tRNA fragments with random 3′-terminal extensions among oligonucleotides with Dps-dependent secretion. We observed an exclusive intracellular enrichment of modified LeuT(VPQ) tRNA fragments compared to secretomes, with abundance level dependent on growth medium and the presence of competing bacteria. To assess the pervasiveness of this phenomenon, we developed a custom computational pipeline for detecting variable RNA termini in RNA-seq data. Beyond LeuT(VPQ) tRNA fragments, several other genomic loci yielded oligos with highly heterogeneous ends, indicating that terminal elongation, most prevalent in LeuT(VPQ), is not exclusive to these fragments. Ex vivo testing using synthetic LeuT(VPQ) analogs revealed their stimulatory effect on the persistence of multiple taxa in an artificial microbiome, which was attenuated by 3′-end elongation. We propose that non-template extensions may serve to broaden the spectrum of target molecules for elimination of unused mRNAs by an interference-like mechanism or to generate sequences absent from the E. coli genome as part of a primitive defense system. Full article

According to the International Diabetes Federation, approximately 537 million adults suffered from diabetes in 2021, a number that is projected to rise to 783 million by 2045. Insulin is a hormone produced by the pancreas that regulates blood glucose levels; for people suffering from diabetes, insulin activity may be reduced or absent, and therefore, administration of insulin may be necessary to maintain healthy blood glucose levels. Recombinant human insulin is commercially produced using a variety of host microorganisms, such as bacteria and yeast. Nevertheless, few studies have assessed the environmental impacts associated with different upstream medium formulations and their contribution to the overall environmental footprint of recombinant insulin production. Here, Life Cycle Assessment (LCA) is conducted on various upstream media used in insulin production—including pre-cultivation, growth, feed, and induction media—capturing the impacts associated with both their supply chains and their on-site preparation. Hotspots of environmental impacts are identified, and different alternatives for input materials and process conditions are compared in terms of impacts. The findings reported here can serve to guide process and sustainability optimization of the upstream production process from an operational process perspective. Finally, the identification of hotspots enables the implementation of impact reduction measures in bioprocess design, which have the potential to significantly improve the sustainability of insulin production. Full article

Cephus fumipennis, a significant pest of highland spring wheat, damages crops through larval boring and feeding within wheat stalks. This activity disrupts nutrient and water transport, causing severe yield reductions. To find microbial biocontrol agents targeting this pest, primary entomopathogenic microorganisms were isolated and identified from naturally infected, deceased C. fumipennis larvae. Morphological examination and ITS-based phylogenetic analysis tentatively identified the isolate as the entomopathogenic fungus Clonostachys sp. (strain CF01). Third-instar larvae of C. fumipennis were inoculated with conidial suspensions of the CF01 strain at concentrations of 1 × 10⁵, 1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ spores/mL. Spore suspensions of different concentrations demonstrated pathogenicity against third-instar larvae of C. fumipennis. The optimal growth conditions for strain CF01 were identified as follows: PPDA medium, 25 °C, fructose as the carbon source, and yeast extract as the nitrogen source. Photoperiod exhibited no significant effect on either mycelial growth or sporulation. These findings indicate that the CF01 strain possesses considerable potential for the biocontrol of C. fumipennis. Full article

Microbial-enhanced oil recovery (MEOR) is a promising technology for oilfield development. To improve MEOR efficiency, two functional strains—Bacillus mucilaginosus ZZ-8 and Bacillus amyloliquefaciens ZZ-11—were isolated and purified. The growth characteristics, biosurfactant production, and crude oil emulsification performance of these strains were systematically evaluated through single-strain cultures and a co-culture system (ZZ-8: ZZ-11 = 1:1). The results demonstrated that the co-culture system exhibited superior growth and functional performance compared to monocultures. The cell-free supernatant significantly reduced oil–water interfacial tension, decreasing the contact angle from 53.56 ± 1.3° to 28.78 ± 0.82°, thereby enhancing crude oil detachment from rock surfaces and improving oil displacement efficiency. Gas chromatography (GC) analysis further confirmed the co-culture system’s pronounced degradation of long-chain alkanes (C17–C35). In oil sand washing experiments, the 1:1 mixed-strain fermentation broth achieved a crude oil elution rate of 84.39%, representing an 89.80% increase over uninoculated medium. This study not only validates the synergistic effect of the B. mucilaginosus–B. amyloliquefaciens co-culture system in enhancing oil recovery but also provides a theoretical foundation and innovative strategy for its practical application in MEOR technology. Full article

Although epidermal growth factor (EGF) has potential wide applications in the cosmetic industry, it still has limitations, such as a costly purification process and low stability in the surrounding environment. To overcome these limitations, we developed genetically modified Pediococcus pentosaceus CBT SL4, which can secrete EGF protein in growth media, thereby producing probiotic-derived PP-EGF culture medium supernatant (PP-EGF-SUP). Even at low EGF concentrations, PP-EGF-SUP exhibited EGF activities, such as cell scratch wound healing, tyrosinase inhibition, and improvements in anti-wrinkle factors, similar to or stronger than those of recombinant human EGF (rhEGF), which was used as a positive control. PP-EGF-SUP exhibited strong additional biological activities, such as antioxidant, anti-inflammatory, and anti-microbial activities, even though rhEGF did not have such properties. PP-EGF-SUP could be easily transformed to PP-EGF-SUP dried powder (PP-EGF-DP) using the freeze-drying method, and it could also be well resolved in water up to 20 mg/mL; furthermore, it still maintained its bioactivity after the manufacturing process. To determine melasma improvement efficacy, a human application test was performed using melasma ampoules containing 1% or 5% PP-EGF-DP formulations for four weeks. When comparing the melasma values before and after treatment, it was found that the light melasma value statistically decreased by 3.38% and 3.79% and that the dark melasma value statistically decreased by 1.74% and 2.93% in the test groups applying the 1% and 5% PP-EGF-DP melasma ampoules, respectively. In addition, the melasma area also decreased by 21.21% and 29.1%, while the control group showed no statistical difference. During the study period, no significant adverse skin reactions were observed due to the application of the PP-EGF-DP melasma ampoule. In conclusion, PP-EGF-DP may offer unique advantages in the cosmetic ingredient market, such as safety (as a probiotic derivative), stability (postbiotics protect EGF activity), and diverse bioactivities (activity potentiation and postbiotic-derived biological activities). Full article

This study investigated the feasibility of using both the solid and the liquid fractions of waste from the anaerobic digestion process—the digestate—as a possible liquid growth medium for fungal production of chitosan. An enriched liquid phase (ELP), combining both fractions, and derived from mild acid hydrolysis treatment at 120 °C with 6% H₂SO₄ (w/v) for 70 min, was screened for its ability to support biomass and chitosan production by 17 fungal strains. The best results were obtained with Absidia blakesleeana NRRL 2696 and Rhizopus oryzae NRRL 1510 cultures, which yielded chitosan volumetric productions of 444 and 324 mg L⁻¹, respectively. The chitosan preparations of the former and the latter strain, characterized by infrared spectroscopy, elemental analysis, viscosimetry and thermogravimetric analysis, showed deacetylation degrees of 79% and 84.2%, respectively, and average viscosimetric molecular weights of around 20 and 5.4 kDa, respectively. Moreover, both fungal chitosan samples exerted significant antibacterial activity towards Gram-negative (i.e., Pseudomonas syringae and Escherichia coli) and Gram-positive (i.e., Bacillus subtilis) species. Full article

Various pretreatment methods for the valorization of sunflower husks (SHs) for H₂ gas generation through fermentation by Escherichia coli were investigated. We analyzed thermal treatment (TT), acid hydrolysis (AH), and alkaline hydrolysis (AlkH) at different substrate concentrations (50 g L⁻¹, 75 g L⁻¹, 100 g L⁻¹, and 150 g L⁻¹) and dilution levels (undiluted, 2× diluted, and 5× diluted). A concentration of 75 g L⁻¹ SH that was acid-hydrolyzed and dissolved twice in the medium yielded optimal microbial growth, reaching 0.3 ± 0.1 g cell dry weight (CDW) L⁻¹ biomass. The highest substrate level enabling effective fermentation was 100 g L⁻¹, producing 0.37 ± 0.13 (g CDW) × L⁻¹ biomass after complete fermentation, while 150 g L⁻¹ exhibited pronounced inhibitory effects. It is worth mentioning that the sole alkaline treatment was not optimal for growth and H₂ production. Co-fermentation with glycerol significantly enhanced both biomass formation (up to 0.42 ± 0.15 (g CDW) × L⁻¹)) and H₂ production. The highest H₂ yield was observed during batch growth at 50 g L⁻¹ SH hydrolysate with 5× dilution, reaching up to 5.7 mmol H₂ (g sugar)⁻¹ with glycerol supplementation. This study introduces a dual-waste valorization strategy that combines agricultural and biodiesel industry residues to enhance clean energy generation. The novelty lies in optimizing pretreatment and co-substrate fermentation conditions to maximize both biohydrogen yield and microbial biomass using E. coli, a widely studied and scalable host. Full article