Bacteria produce poly (γ‐glutamic acid) (γ‐PGA), a polymer of l‐ or d‐glutamic acid, as a defense response and have gained importance due to their applications in food and pharmaceutical industry. In the present investigation, production of γ‐PGA using cost‐effective carbon substrate, characterization of the produced polymer, and its application as cryoprotectant for selected freeze‐dried probiotic bacteria were investigated. Central composite rotatable design of response surface methodology was used to study the main and the interactive effects of medium components: rice bran and casein peptone concentration. Rice bran at 35% (w/v) and casein peptone at 7.5% (w/v) were found to be optimal at an initial pH of 7.5, and incubation temperature of 37°C for 48 H produced 8.2 g/L γ‐PGA on dry weight basis. The thermal properties such as melting temperature, heat of fusion, and thermal stability were also studied. Ten percent (w/v) of γ‐PGA with 10 percent of sodium alginate (w/v) protected viability of Bifidiobacterium bifidum NCDC 235 and B. adolescentis NCDC 236 during freeze drying at –80 ˚C for 48 H. The γ‐PGA synthesized by the reported bacterium with GRAS status is suitable for food and biomedical applications.

中文翻译：

---

利用地衣芽孢杆菌优化生产聚（γ-谷氨酸）（γ-PGA）及其作为益生菌的冷冻保护剂的应用。

细菌产生聚（γ-谷氨酸）（γ-PGA），是l或d的聚合物谷氨酸作为防御反应，由于其在食品和制药行业中的应用而变得越来越重要。在本研究中，研究了使用具有成本效益的碳底物生产γ-PGA，表征所生产的聚合物及其在选定的冻干益生菌中作为冷冻保护剂的应用。使用响应面方法的中央复合可旋转设计研究了米糠和酪蛋白p浓度等主要成分的交互作用。发现35％（w / v）的米糠和7.5％（w / v）的酪蛋白p在初始pH值为7.5时是最佳的，37°C的孵育温度48 H产生8.2 g / Lγ- PGA以干重计。还研究了熔融温度，熔融热和热稳定性等热性能。双歧杆菌双歧杆菌NCDC 235和青春双歧杆菌NCDC 236在–80˚C下冷冻干燥48H 。据报道，该细菌以GRAS状态合成的γ-PGA适用于食品和生物医学应用。