Search Results (103)

This study aimed to isolate Bacillus strains producing poly-γ-glutamic acid (γ-PGA), a natural antioxidant biopolymer, from Cheonggukjang, optimize fermentation conditions, improve γ-PGA production in the food by applying the selected strain, and investigate its potential association with antioxidant activity. Among 157 isolates, Bacillus velezensis CH7P29 demonstrated the highest γ-PGA production (602.80 ± 6.55 μg/mL) and was selected for fermentation. Optimal in vitro conditions for γ-PGA production were determined as 40 °C and 0–2% NaCl. In Cheonggukjang fermentation under optimal conditions, the CH7P29-inoculated group exhibited a marked increase in γ-PGA content (16.02 mg/g on day 4), which was significantly higher than the uninoculated control (not detected) and reference strain groups (12.25 and 11.38 mg/g, respectively). Simultaneously, its DPPH radical scavenging activity exceeded 60%, and γ-PGA content strongly correlated with antioxidant activity (R = 0.95). Conversely, total polyphenol content remained stable, indicating that γ-PGA and microbial metabolites contributed primarily to antioxidant activity. Further analysis supported this by showing that γ-PGA accounted for 37.40% of the total DPPH radical scavenging activity in the CH7P29-inoculated group at the end of fermentation. These data emphasize that B. velezensis CH7P29 is a promising functional starter culture for enhancing the biofunctional properties of Cheonggukjang and fermented soybean food. Full article

Moderate electric field (MEF) fermentation was investigated as a nonthermal stress strategy to enhance the formation of extracellular polymeric substances (EPS; mucilage) by Bacillus subtilis HA in a Haematococcus-based medium. Response surface methodology (RSM), combined with a Box–Behnken design, was employed to optimize the fermentation medium composition and the MEF operating parameters. Under conventional fermentation (CF), the optimized medium (2.91% Haematococcus pluvialis, 3.10% glucose, and 13.42% L-glutamate) yielded 8.60 ± 0.25% mucilage, closely matching the predicted value (8.54%) and confirming model adequacy. The optimized MEF conditions (85.2 Hz, 0.29 A, and 40.90% duty cycle) increased mucilage formation to 13.59 ± 0.18%, corresponding to approximately 1.6-fold enhancement compared with CF. Statistical analysis indicated that frequency–current interactions and a nonlinear duty cycle response governed EPS accumulation. Substrate–metabolite analysis further showed that MEF significantly reduced residual L-glutamate (1.25 ± 0.03%) while increasing poly-γ-glutamic acid (γ-PGA) content (11.07 ± 0.16%), indicating enhanced conversion of L-glutamate into γ-PGA-rich mucilage. In comparative physicochemical stress experiments, 3% KCl supplementation produced the highest mucilage formation among non-MEF conditions. The MEF-treated system achieved the highest mucilage production, indicating that MEF is a tunable and effective strategy for promoting substrate-to-polymer conversion and regulating EPS production in Bacillus-based fermentation systems. Full article

The current study illustrates the modeling of a biocompatible poly γ-glutamic acid (PGA)–chitosan–rGO nanocomposite hydrogel scaffold, which showed a promising novel scaffold for stimulating central nerve regeneration that addresses the shortcomings of recent therapies and improves tissue engineering, controls inflammation, and restores lost functions after spinal cord injuries (SCIs). In the implementation part of the study, the COMSOL program’s top-notch modeling of a detailed investigation of how a scaffold’s in vivo diffusion affects injured neurons. Michaelis–Menten kinetics is used to characterize the enzyme process of releasing the outer covering shell of the scaffold, PGA, from a biomaterial matrix to the nerve cell. Results suggested that the injectable hydrogel scaffold theoretically reduces extracellular glutamate concentrations, presenting a potential mechanism to mitigate localized excitotoxicity. Future in vivo experimental validation is required to determine if this reduction prevents neural cell death Full article

Drought stress severely restricts agricultural productivity. Effective drought mitigation requires both improved rhizosphere water retention and enhanced nutrient availability. Poly-γ-glutamic acid (PGA) was expected to enhance water retention, while residue after evaporation (RAE) of 2-keto-L-gulonic acid fermentation was expected to supply labile carbon and promote nutrient mobilization. We hypothesized that their combined application would synergistically optimize the rhizosphere environment and enhance maize seedlings’ resistance to drought. A pot experiment was conducted to evaluate the growth of maize under simulated drought conditions, containing four treatments: control (C), RAE alone (R), PGA alone (P), and their combination (M). Results demonstrated that the M treatment synergistically promoted maize seedling growth, increasing the seedling growth index by 125% compared to the control. Co-application also synergistically enhanced the accumulation of osmotic adjustment substances (proline, soluble proteins, and soluble sugars) and ascorbic acid content, while reducing malondialdehyde (MDA) level. Furthermore, the M treatment markedly increased soil ammonium nitrogen and total organic carbon, thereby improving soil moisture and optimizing the rhizosphere conditions. Mantel analysis revealed that the M treatment restructured soil bacterial communities and enzyme activities by enhancing nutrient and organic carbon availability, which subsequently improved overall soil properties. These findings suggest that co-application of PGA and RAE improves maize seedling drought resilience and soil nutrient supply, offering a promising and economically viable strategy for sustainable agriculture in drought-prone regions by valorizing industrial by-products. Full article

Poly-γ-glutamic acid (γ-PGA) can regulate soil physicochemical properties and enhance crop yield. However, the effect of γ-PGA molecular weight (Mw) on plant growth remains unclear. In this study, we investigated the effects of γ-PGAs with low (70–100 kDa), high (700–1100 kDa), and ultra-high (>3000 kDa) Mws on lettuce growth and soil properties. The results showed that γ-PGA application reduced the infiltration rate of red soil. In pot experiments, γ-PGAs with different Mws at 0.1% promoted lettuce growth, and blade length and width increased with increasing Mw. However, the excessive application of ultra-high Mw γ-PGA inhibited lettuce growth. Soil chemical properties revealed that γ-PGA treatments significantly increased soil ammonium nitrogen and available potassium content. Furthermore, bacterial community structure analysis indicated that adding γ-PGA reduced bacterial diversity and richness, particularly under low and high Mw γ-PGA treatments, while increasing the relative abundance of beneficial plant-associated bacteria, including Proteobacteria and Acidobacteriota. Overall, ultra-high Mw γ-PGA exhibited the strongest effects on soil water retention and nutrient regulation, whereas low application rate was more favorable for plant growth. These findings can provide insights into the agricultural application of γ-PGA. Full article

Optimizing calcium metabolism is crucial for skeletal development and overall productivity in growing ruminants. Twenty-four Sunite lambs were randomly assigned to four groups and fed 0, 0.6, 1.2, or 2.4 g/(d·head) of γ-PGA for 60 days. Growth performance, serum parameters, duodenal morphology and calcium transporter expression, bone microarchitecture, and duodenal microbiota were analyzed. Supplementation with 1.2 g/(d·head) of γ-PGA (the M group) yielded optimal results, significantly improving final body weight and size. It enhanced duodenal health, evidenced by increased villus height, crypt depth, and microvilli density. Crucially, this dose significantly upregulated the expression of key duodenal calcium transporters (TRPV5/6, CaBPD9k, PMCA, VDR, claudin-12) and altered systemic calcium-regulating hormones (elevated calcitriol, PTH, FGF23). Bone micro-CT analysis revealed changes in trabecular architecture indicative of active remodeling. 16S rRNA sequencing and weighted OTU co-expression network analysis (WOCNA) revealed that γ-PGA reshaped the duodenal microbiota and identified core microbial modules strongly associated with host phenotypes. Genera such as [Eubacterium]_ruminantium_group, Fusicatenibacter, and Prevotella emerged as central hubs. In conclusion, dietary γ-PGA at 1.2 g/(d·head) enhances calcium absorption and bone metabolism in lambs through a coordinated modulation of intestinal integrity and calcium transport, systemic endocrine responses, and the duodenal microbial community, with specific microbiota identified as potential key mediators associated with these effects. Full article

Low-temperature stress significantly limits wheat growth and productivity. Poly-γ-glutamic acid (γ-PGA) is an environmentally friendly green molecular material that plays an important role in plant growth and regulation; however, its protective mechanisms against cold stress in wheat remain poorly understood. In this study, the effect of γ-PGA on both chilling (4 °C) and freezing (−18 °C) resistance in wheat seedlings and its underlying mechanisms were comparatively studied. The results showed that the γ-PGA-treated seedlings exhibited a 128.81% higher survival rate after freezing stress and maintained significantly greater biomass accumulation under both stress conditions (62.44% and 26.56% higher dry weight under chilling and freezing stress, respectively). A physiological analysis revealed that γ-PGA enhanced osmoprotectant (proline and soluble sugars) accumulation and activated key antioxidant enzymes (SOD, POD, and APX). Then, an RNA-seq analysis identified 11,401 and 7721 differentially expressed genes under chilling and freezing stress, respectively, with 3598 common genes constituting a core cold-response network. KEGG and GO analyses demonstrated significant enrichment in pathways related to carbon metabolism, glutathione metabolism, phenylpropanoid–flavonoid biosynthesis, fatty acid metabolism, and cell wall organization. Notably, γ-PGA strongly upregulated key genes in phenylpropanoid–flavonoid metabolism (TraesCS2B02G615000 and TraesCS2B02G624400), glutathione metabolism (TraesCS1B02G127900), and lipid metabolism (TraesCS1B02G018700). These results provide comprehensive molecular insights into γ-PGA-mediated cold tolerance and support its potential application in sustainable wheat production under low-temperature stress conditions. Full article

Soil salinization is a major threat to agricultural sustainability. Poly-gamma-glutamic acid (γ-PGA), a biopolymer produced by microbial fermentation, has received attention as a biostimulant due to its positive effects on crop performance. However, the function of γ-PGA in crop salt stress tolerance and its effect on the rhizosphere are unclear. This study explores the effects of γ-PGA application on rhizosphere soil nutrients and the soil–physical environment and examines the salt tolerance response of maize seedlings grown in saline–alkali soil under such an application regime. The results show a significant promotion of maize seedling growth and of nutrient accumulation with γ-PGA application under salt stress; plant dry weight, stem diameter, and plant height increased 121%, 39.5%, 18.4%, respectively, and shoot accumulation of nitrogen, phosphorus, potassium, and carbon increased by 1.38, 2.11, 1.50, and 1.36 times, respectively, under an optimal-concentration γ-PGA treatment (5.34 mg kg⁻¹ (12 kg ha⁻¹)) compared with the control. γ-PGA treatment significantly decreased rhizospheric pH and soil electrical conductivity and significantly increased nutrient availability in the rhizosphere, especially available nitrogen (AN) and available potassium (AK). Compared with the control, AN, available phosphorus (AP), and AK increased by 13.9%, 7.70%, and 17.7%, respectively, under an optimal concentration treatment with γ-PGA. γ-PGA application also significantly increased the activities of urease, acid phosphatase, alkaline phosphatase, dehydrogenase, and cellulose in rhizosphere soil by 35.5–39.3%, 35.4–39.3%, 5.59–8.85%, 18.9–19.8%, and 19.2–47.0%, respectively. γ-PGA application significantly decreased Na⁺ concentration and increased K⁺ concentration in shoots, resulting in a lowering of the Na⁺/K⁺ ratio by 30.5% and an increase in soluble sugar and soluble protein contents. Therefore, rhizosphere application of water-soluble and biodegradable γ-PGA facilitates the creation of an optimized rhizospheric environment for maize seedling and overcomes osmotic and ionic stresses, offering possibilities for future use in drip-irrigation systems in the cultivation of crops on saline-alkali land. Full article

Extracellular poly-γ-glutamic acid (γ-PGA) produced by Bacillus species demonstrates significant antibacterial properties, positioning it as a promising candidate for diverse biomedical and industrial applications. This study focused on molecular identification of Bacillus subtilis using Polymerase Chain Reaction (PCR) and evaluated the initial production of γ-PGA from a novel biological source of Bacillus subtilis. Shake flask fermentation was utilized for γ-PGA production, with three distinct growth media (Tryptic, MRS, and Mineral medium) assessed for their efficiency in polymer yield. Characterization of γ-PGA was conducted through FT-IR, HPLC, and GC-MS analyses. FT-IR spectroscopy confirmed the presence of characteristic functional groups such as carbonyl, amide, and hydroxyl groups. HPLC and GC-MS analyses provided insights into the polymer’s purity and molecular composition, highlighting components like methyl esters, hexanoic acid, and monomethyl esters. Furthermore, the study quantified γ-PGA production during a four-day shake flask fermentation period. These findings contribute significantly to bacterial characterization, optimization of fermentation processes, and the exploration of γ-PGA’s potential as an antibacterial agent. Future research directions include refining purification techniques to enhance γ-PGA’s antibacterial efficacy and expanding its applications across various fields. Full article

Background: Articular cartilage has limited self-repair capacity. While thermoresponsive poly N-isopropyl acrylamide (pNIPAAm)-based Cell Sheet Engineering (CSE) is a promising scaffold-free strategy, its inherent material properties pose limitations. This study developed and validated a novel, non-thermoresponsive CSE platform for functional cartilage regeneration. Methods: A culture platform was fabricated by grafting the biocompatible polymer poly gamma-glutamic acid (γ-PGA) and a disulfide-containing amino acid onto porous PET membranes. This design enables intact cell sheet detachment with its native extracellular matrix (ECM) via specific cleavage of the disulfide bonds by a mild reducing agent. Results: The hydrated substrate exhibited a biomimetic stiffness (~16.2 MPa) that closely mimics native cartilage. The platform showed superior biocompatibility and supported the cultivation of multi-layered rabbit chondrocyte sheets rich in Collagen II and Glycosaminoglycans. Critically, in a rabbit full-thickness defect model, transplanted autologous cell sheets successfully regenerated integrated, hyaline-like cartilage at 12 weeks, as confirmed by MRI, CT, and histological analyses. Conclusions: This novel CSE platform, featuring highly biomimetic stiffness and a gentle, chemically specific detachment mechanism, represents a highly promising clinical strategy for repairing articular cartilage defects. Full article

Poly-γ-glutamic acid (γ-PGA), also known as polyglutamate, is a naturally derived polymer produced by Bacillus species that has demonstrated antiviral properties. Growing evidence from preclinical and clinical studies supports its therapeutic potential against various viral infections, highlighting both effective antiviral activity and a favorable safety profile. This review emphasizes current findings on the antiviral mechanisms of γ-PGA, including its ability to interfere with viral entry and to activate serial immune signaling pathways, with additional insights from structural biology. Collectively, γ-PGA represents a promising biomaterial for the development of future broad-spectrum antiviral strategies and applications. Full article

This review overviews the efficient hydrophobization method of hydrophilic natural polymers, which has been developed by means of glucan phosphorylase (GP)-induced enzymatic grafting of unnatural heteropolysaccharides, that is, partially 2-deoxygenated (P2D)-amyloses. The enzymatic polymerization technique is well known as a useful approach to prepare polysaccharides with well-defined structures. The authors have found that the hydrophobicity of P2D-amylose, synthesized by the thermostable GP (from Aquifex aeolicus VF5)-induced enzymatic copolymerization of α-d-glucose 1-phosphate (Glc-1-P)/d-glucal as comonomers, started from maltooligosaccharide primers. Based on this finding, glycogen, a hydrophilic spherical natural polysaccharide, was hydrophobized by means of the thermostable GP-induced enzymatic functionalization of the P2D-amylose chains because glycogen acted as the polymeric primer for the GP catalysis. After introducing the maltooligosaccharide primers onto hydrophilic natural polymers with carboxylate groups—such as poly(γ-glutamic acid), carboxymethyl cellulose, and alginic acid—via chemical reactions, the thermostable GP-induced enzymatic copolymerization of Glc-1-P/d-glucal was carried out using the resulting polymeric primers, enabling their hydrophobization through the grafting of P2D-amylose chains (the chemoenzymatic approach). Moreover, the chemoenzymatic method has extensively been employed for hydrophobization of the surfaces on natural polysaccharide nanofibers, such as cellulose and chitin nanofibers. Full article

Background/Objectives: Nanogels (NGs) are promising carriers for drug delivery due to their tunable size, biocompatibility, and capability to encapsulate sensitive molecules. However, conventional batch synthesis often lacks control over key parameters, such as size distribution and encapsulation efficiency. This study aimed to develop a microfluidic platform for the reproducible synthesis of poly(α-glutamic acid) (PGA)-based NGs using strain-promoted azide–alkyne cycloaddition (SPAAC) click chemistry and to investigate the effects of flow parameters on the physicochemical properties of nanogels. Methods: Functionalized PGAs (with azide and DBCO) were co-injected into a microfluidic system within a flux of acetone to form NGs via SPAAC. Flow rate ratios (FRR) and total flow rates were systematically screened at 25 °C, with tests at 50 °C. We evaluated the particle size, polydispersity index (PDI), zeta potential, and encapsulation efficiency (EE%) of doxorubicin-loaded NGs. Results: NGs with tunable sizes ranging from ~50 nm to >170 nm and low PDI (<0.1 in optimal conditions) were obtained. Higher FRR and total flow rates yielded smaller and more uniform NGs. Doxorubicin loading did not affect the nanogel size and uniformity, and in some cases, it improved them. The EE% reached up to ~65%, and ~40% for the best formulations. Elevated temperature improved the characteristics of drug-loaded nanogels at intermediate solvent ratios. Compared to batch synthesis, the microfluidic process offers enhanced reproducibility and size control. Conclusions: Microfluidic SPAAC synthesis enables precise and scalable fabrication of PGA NGs with controllable size and drug loading. This platform supports future integration of on-chip purification and monitoring for clinical nanomedicine applications. Full article

Soil contamination with petroleum hydrocarbons is a serious environmental issue, necessitating the development of effective and environmentally friendly remediation methods that align with the principles of sustainable development. This study investigated the impact of selected biosurfactants on the efficiency of the biodegradation of total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) in contaminated soil. Six biosurfactants—poly-γ-glutamic acid (γ-PGA), rhamnolipid, surfactin, a mixture of γ-PGA, rhamnolipids, and surfactin (PSR), as well as two commercial formulations (JBR 425 and JBR 320)—were evaluated in combination with a bacterial consortium. Biodegradation experiments were conducted under laboratory conditions for a 90-day period. The effectiveness of the tested biosurfactants was assessed using respirometric analysis, the chromatographic determination of the residual hydrocarbon content, and toxicity assays. The results showed that the application of a bacterial consortium enriched with a mixture of biosurfactants PSR (a biosurfactant concentration in the inoculating mixture: 5 g/dm³) was the most effective approach, resulting in an oxygen uptake of 5164.8 mgO₂/dm³ after 90 days, with TPH and PAH degradation rates of 77.3% and 70.32%, respectively. Phytotoxicity values decreased significantly, with TU values ranging from 6.32 to 4.62 (growth inhibition) and 3.77 to 4.13 (germination). Toxicity also decreased in the ostracodtoxkit test (TU = 4.35) and the Microtox SPT test (TU = 4.91). Among the tested biosurfactants, surfactin showed the least improvement in its bioremediation efficiency. Under the same concentration as in the PSR mixture, the oxygen uptake was 3446.7 mgO₂/dm³, with TPH and PAH degradation rates of 60.64% and 52.64%, respectively. In the system inoculated with the bacterial consortium alone (without biosurfactants), the biodegradation efficiency reached 44.35% for TPH and 36.97% for PAHs. The results demonstrate that biosurfactants can significantly enhance the biodegradation of petroleum hydrocarbons in soil, supporting their potential application in sustainable bioremediation strategies. Full article

Whey protein isolate (WPI) hydrogel is a promising candidate as a biomaterial for tissue engineering. Previously, WPI hydrogels containing poly-γ-glutamic acid (γ-PGA) with a molecular weight (MW) of 440 kDa demonstrated potential as scaffolds for bone tissue engineering. Here, the study compares different γ-PGA preparations of differing MW. WPI-γ-PGA hydrogels containing 40% WPI and 0%, 2.5%, 5%, 7.5%, and 10% γ-PGA were synthesised. Three γ-PGA MWs were compared, namely 10 kDa, 700 kDa, and 1100 kDa. Evidence of successful γ-PGA incorporation was demonstrated by scanning electron microscopy and Fourier transform infrared spectroscopy. Increasing γ-PGA concentration significantly improved the swelling potential of the hydrogels, as demonstrated by ratio mass increases of between 85 and 90% for each 10% variable group. Results suggested that γ-PGA delayed enzymatic proteolysis, potentially decreasing the rate of degradation. The addition of γ-PGA significantly decreased the Young’s modulus and compressive strength of hydrogels. Dental pulp mesenchymal stem cells proliferated on all hydrogels. The highest cellular growth was observed for the WPI-700 kDa γ-PGA group. Additionally, superior cell attachment was observed on all WPI hydrogels containing γ-PGA compared to the WPI control. These results further suggest the potential of WPI hydrogels containing γ-PGA as biomaterials for bone tissue engineering. Full article