枯草芽孢杆菌 PG-001 发酵生产 γ-PGA 及其葡萄糖反馈控制 pH -stat 策略。
γ-PGA Fermentation by Bacillus subtilis PG-001 with Glucose Feedback Control pH-stat Strategy.
机构信息
State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, People's Republic of China.
出版信息
Appl Biochem Biotechnol. 2022 May;194(5):1871-1880. doi: 10.1007/s12010-021-03755-x. Epub 2022 Jan 6.
Poly-γ-glutamic acid (γ-PGA) is an important biopolymer with many applications due to its biodegradable and non-toxic characteristics. γ-PGA is produced industrially by fermentation of Bacillus species. The optimal pH range for producing γ-PGA by Bacillus subtilis PG-001 was firstly studied by glucose fed-batch fermentation with non-controlled pH. Result showed that both cell growth and γ-PGA synthesis were repressed when pH was lower than pH 6. Further investigation with γ-PGA fed-batch fermentation showed that pH 6.5 is more suitable for γ-PGA fermentation than pH 7. Under comparable consumption of glutamic acid and glucose, 11.8 g/L γ-PGA and 0.7 g/g yield were achieved by fermentation at pH 6.5, which was significantly higher than 10.5 g/L and 0.56 g/g yield of fermentation at pH 7. In addition, γ-PGA degradation during later phase of fermentation was repressed at pH 6.5 as 9238cP of final broth viscosity was achieved from fermentation at pH 6.5 while it was only 346 cP for fermentation at pH 7. Finally, a glucose feedback control pH-stat strategy was performed for reducing alkali consumption during γ-PGA fermentation, which further increased final γ-PGA concentration to 15.5 g/L with much higher viscosity (11458 cP); meanwhile the consumption of alkali decreased 57%. The fed-batch γ-PGA fermentation with glucose feedback control pH-stat strategy showed high feasibility for industrial scaling-up.
聚-γ-谷氨酸(γ-PGA)是一种具有重要应用价值的生物聚合物,由于其可生物降解和无毒的特性。γ-PGA 是通过发酵棒状杆菌属工业生产的。首先通过葡萄糖分批补料发酵非控制 pH 值研究了枯草芽孢杆菌 PG-001 生产 γ-PGA 的最佳 pH 范围。结果表明,当 pH 值低于 6 时,细胞生长和 γ-PGA 合成都受到抑制。进一步用 γ-PGA 分批补料发酵进行的研究表明,pH6.5 比 pH7 更适合 γ-PGA 发酵。在谷氨酸和葡萄糖消耗相当的情况下,在 pH6.5 下发酵可获得 11.8g/Lγ-PGA 和 0.7g/g 的产率,明显高于在 pH7 下发酵的 10.5g/L 和 0.56g/g 的产率。此外,在 pH6.5 下发酵可抑制发酵后期 γ-PGA 的降解,最终发酵液的黏度达到 9238cP,而在 pH7 下发酵仅为 346cP。最后,进行了葡萄糖反馈控制 pH -stat 策略以减少 γ-PGA 发酵过程中的碱消耗,这进一步将最终 γ-PGA 浓度提高到 15.5g/L,黏度更高(11458cP);同时碱的消耗减少了 57%。具有葡萄糖反馈控制 pH-stat 策略的分批补料 γ-PGA 发酵具有很高的工业放大可行性。