Institute of Biotechnology, Vietnam Academy of Science and Technology, Hanoi, 100000, Vietnam.
Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, 100000, Vietnam.
World J Microbiol Biotechnol. 2022 Aug 3;38(10):173. doi: 10.1007/s11274-022-03364-8.
Poly-γ‑glutamic acid (γ‑PGA) produced by Bacillus species is a natural biopolymer, which is widely used in various fields including food, pharmaceuticals, and cosmetics. In this study, the screening of 19 Bacillus isolates derived from traditionally fermented foods revealed that Bacillus velezensis VCN56 was the most potent γ‑PGA producer. The maximum concentration of crude γ‑PGA was 32.9 ± 1.5 g/L in the PGA-3 medium containing glycerol, citric acid, sodium glutamate, NHCl, and starch. The resulting γ-PGA was purified and then characterized by HPLC, FTIR, and H-NMR analyses. Molecular weight of purified γ‑PGA was estimated to be 98 kDa with a polydisperse index of 2.04. Notably, the pure γ‑PGA showed significant in vitro antioxidant scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (72.0 ± 1.5%), hydroxyl (81.0 ± 0.6%), and superoxide (43.9 ± 0.8%) radicals at the concentration of 4 mg/mL. Using whole-genome sequencing, the genetic organization of pgs operon responsible for γ‑PGA biosynthesis in B. velezensis VCN56 differs from those in other Bacillus genomes. Further genome analysis revealed metabolic pathways for γ-PGA production and degradation. For the first time, the present study provides a better understanding of γ-PGA with a promising antioxidant activity produced by B. velezensis at the phenotypic, biochemical, and genomic levels, which hold potential applications in the foods, cosmetics, and pharmaceutical industries.
聚-γ-谷氨酸（γ-PGA）是一种由芽孢杆菌属产生的天然生物聚合物，广泛应用于食品、制药和化妆品等各个领域。在本研究中，对源自传统发酵食品的 19 株芽孢杆菌分离物进行筛选，结果表明，解淀粉芽孢杆菌 VCN56 是最具潜力的 γ-PGA 生产菌。在含有甘油、柠檬酸、谷氨酸钠、NH4Cl 和淀粉的 PGA-3 培养基中，该菌最大 γ-PGA 产量可达 32.9 ± 1.5 g/L。所得 γ-PGA 经纯化后，通过 HPLC、FTIR 和 H-NMR 分析进行鉴定。经测定，纯化 γ-PGA 的分子量约为 98 kDa，多分散指数为 2.04。值得注意的是，纯 γ-PGA 在 4 mg/mL 浓度下对 1,1-二苯基-2-苦基肼（72.0 ± 1.5%）、羟基（81.0 ± 0.6%）和超氧自由基（43.9 ± 0.8%）具有显著的体外抗氧化清除活性。通过全基因组测序，发现解淀粉芽孢杆菌 VCN56 中 pgs 操纵子的遗传组织与其他芽孢杆菌基因组中的操纵子不同，负责 γ-PGA 生物合成。进一步的基因组分析揭示了 γ-PGA 的生产和降解代谢途径。本研究首次从表型、生化和基因组水平全面解析了具有潜在抗氧化活性的解淀粉芽孢杆菌产生的 γ-PGA，为其在食品、化妆品和制药行业的应用提供了理论依据。
