Search Results (96)

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

In this study, a Bacillus velezensis SDU strain capable of producing poly-γ-glutamate (γ-PGA) was newly identified from the rhizosphere soil of Baimiao taro. The strain is a glutamate-independent strain and can produce polyglutamic acid in a culture medium completely free of glutamate. The hydrolyzed product of the polyglutamic acid produced is D-glutamic acid. The molecular weight of γ-PGA, estimated via the Mark–Houwink equation, was 1390 kDa. Furthermore, the molecular weight measured by Waters gel permeation chromatography with multi-angle laser light scattering (GPC–MALLS) was 1167 kDa. The production of γ-PGA and its antioxidant and tyrosine inhibition properties were investigated. The γ-PGA production reached 23.1 g/L, and the productivity was 0.77 g L⁻¹ h⁻¹. Specifically, γ-PGA exhibited superoxide anion (·O₂⁻) radical scavenging activity and tyrosinase inhibitory activity. This study introduces a promising strain and a highly efficient application method for γ-PGA, which can be broadly utilized in the pharmaceutical, food, and cosmetic industries. Full article

Rapid industrialization has led to significant environmental challenges, particularly in wastewater treatment, where the removal of heavy metal ions and organic dyes is critical. This study presents the synthesis and characterization of a high-performance hydrogel adsorbent, (nanoclay)_x@poly-γ-glutamic acid (γ-PGA)/polyethyleneimine (PEI) hydrogel adsorbent (denoted as N_xPP, x = 0, 20, 40, 60, and 80), for the efficient removal of heavy metal ions (Cu²⁺, Fe³⁺, and Zn²⁺) and organic dyes (Methylene blue, as a typical example) from wastewater. The hydrogel was prepared using a one-pot method, combining γ-PGA and PEI with varying amounts of nanoclay. The N₈₀PP hydrogel demonstrated exceptional adsorption capacities, achieving 224.37 mg/g for Cu²⁺, 236.60 mg/g for Fe³⁺, and 151.95 mg/g for Zn²⁺ within 30 min, along with 88.18 mg/g for Methylene blue within 5 h. The incorporation of nanoclay significantly enhanced the mechanical properties, with compressive strength reaching 560.49 kPa. The hydrogel exhibited excellent reusability, maintaining high adsorption capacity after five cycles. The adsorption kinetics followed a pseudo-second-order model, and the isotherms fit the Freundlich model, indicating a multilayer adsorption mechanism. This study highlights the potential of N_xPP hydrogels as a versatile and sustainable solution for wastewater treatment. Full article

This review offers an in-depth analysis of microbial γ-poly-glutamic acid (γ-PGA), highlighting its production, biosynthetic pathways, unique properties, and extensive applications in the food and health industries. γ-PGA is a naturally occurring biopolymer synthesized by various microorganisms, particularly species of Bacillus. The report delves into the challenges and advancements in cost-effective production strategies, addressing the economic constraints associated with large-scale γ-PGA synthesis. Its biocompatibility, biodegradability, and non-toxic nature make it a promising candidate for diverse industrial applications. γ-PGA’s exceptional water-holding capacity and humectant properties are key to its utility in the food industry. These features enable it to enhance the stability, viscosity, and shelf life of food products, making it a valuable ingredient in processed foods. The review highlights its ability to improve the textural quality of baked goods, stabilize emulsions, and act as a protective agent against staling. Beyond food applications, γ-PGA’s role in health and pharmaceuticals is equally significant. Its use as a drug delivery carrier, vaccine adjuvant, and biofilm inhibitor underscores its potential in advanced healthcare solutions. Full article

Wound healing is a complex biological process involving inflammation, proliferation, and remodeling phases. Effective healing is essential for maintaining skin integrity, driving the need for advanced materials like hydrogels, known for their high water retention and tunable mechanical properties. In this study, we synthesized a biocompatible composite hydrogel composed of γ-polyglutamic acid (γ-PGA) and ε-polylysine (ε-PL) through a Schiff base reaction, forming a stable crosslinked network. Its physicochemical properties, including rheological behavior and swelling capacity, were systematically evaluated. Biocompatibility was assessed via in vitro hemolysis and cytotoxicity assays, and in vivo testing was performed using a full-thickness skin defect model in Sprague Dawley (SD) rats to evaluate wound-healing efficacy. The PGA-PL hydrogel demonstrated excellent physicochemical properties, with a maximum swelling ratio of 65.6%, and biocompatibility as evidenced by low hemolysis rates (<5%) and high cell viability (>80%). It promoted wound healing by inhibiting the inflammatory response, reducing levels of the inflammatory cytokine IL-6, enhancing angiogenesis, and accelerating collagen deposition. The hydrogel showed complete biodegradation within 21 days in vivo without inducing a significant inflammatory response and significantly accelerated wound healing, achieving an 86% healing rate within 7 days compared to 67% in the control group. The PGA-PL composite hydrogel exhibits excellent mechanical strength and biocompatibility, and its effective wound-healing capabilities lay the groundwork for future development and optimization in various tissue engineering applications. Full article

Alcoholic hepatic steatosis (AHS) is a common early-stage symptom of liver disease caused by alcohol consumption. Accordingly, several aspects of AHS have been studied as potential preventive and therapeutic targets. In this study, a novel strategy was employed to inhibit fatty liver accumulation and counteract AHS through the consumption of microorganism-fermented Protaetia brevitarsis larvae (FPBs). By using an AHS rat model, we assessed the efficacy of FPB by examining the lipid profile of liver/serum and liver function tests to evaluate lipid metabolism modulation. After FPB administration, the lipid profile—including high-density lipoprotein, total cholesterol, and total triglycerides—and histopathological characteristics exhibited improvement in the animal model. Interestingly, AHS amelioration via FPBs administration was potentially associated with poly-γ-glutamic acid (PγG), which is produced by Bacillus species during fermentation. These findings support the formulation of novel natural remedies for AHS through non-clinical animal studies, suggesting that PγG-enriched FPBs are a potentially valuable ingredient for functional foods, providing an ameliorative effect on AHS. Full article

A novel Bacillus subtilis HB-31 strain was isolated from Gotjawal Wetland in Jeju Island, Republic of Korea. A mucus substance produced by this strain was identified as high-molecular-weight poly-γ-glutamic acid (γ-PGA) using NMR, Fourier transform infrared spectroscopy, and size-exclusion chromatography/multi-angle light scattering analyses. We evaluated whether γ-PGA strengthened the skin barrier using keratinocytes and a reconstructed skin model. In keratinocytes, γ-PGA treatment dose-dependently increased the mRNA expression of skin barrier markers, including filaggrin, involucrin, loricrin, serine palmitoyl transferase, fatty acid synthase, and 3-hydroxy-3-methylglutaryl coenzyme A reductase. γ-PGA also enhanced hyaluronic acid synthesis by upregulating hyaluronic acid synthase-1, -2, and -3 mRNA levels and promoted aquaporin 3 expression, which is involved in skin hydration. In the reconstructed skin model, topical application of 1% γ-PGA elevated filaggrin, involucrin, CD44, and aquaporin 3 expression, compared to the control. These results suggest that the newly isolated HB-31 can be used as a commercial production system of high-molecular-weight γ-PGA, which can serve as an effective ingredient for strengthening the skin barrier and improving moisture retention. Further research is needed to explore the long-term effects of γ-PGA on skin health and its application in treating skin conditions. Full article

The presented work discusses the highly efficient esterification of poly (γ-glutamic acid) (γ-PGA) with alkyl halides at room temperature. The esterification reaction was completed within 3 h, and the prepared γ-PGA esters were obtained with excellent yields (98.6%) when 1,1,3,3-tetramethylguanidine (TMG) was used as a promoter. The influence of the amount of TMG, solvent, reaction conditions, and alkyl halides on the esterification reaction was examined. It was found that polar aprotic solvents, such as N-Methylpyrrolidone (NMP) and 1,3-Dimethyl-2-imidazolidinone (DMI), were favorable for the esterification. Non-polar or weakly polar solvents (i.e., dichloroethane, acetonitrile) were not favorable for the esterification. Water as a solvent had a negative effect on esterification. The reactivity of bromine halogenated compounds was higher than that of chlorine halogenated compounds but lower than that of iodine halogenated compounds. The structures of the prepared γ-PGA ester were confirmed by ¹H NMR and FT-IR spectroscopy. Thermal stability and hydrophobic properties of the resulting product were tested. The results showed that the prepared γ-PGA propyl ester had high thermal stability (up to 267 °C) and showed good hydrophobicity (contact angle 118.7°). Full article