Ji Gaosheng, Xu Lishan, Lyu Qingyang, Liu Yang, Gong Xuefeng, Li Xudong, Yan Zhiying
CAS Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, People's Republic of China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Bioprocess Biosyst Eng. 2021 Oct;44(10):2181-2191. doi: 10.1007/s00449-021-02593-9. Epub 2021 Jun 4.
Agricultural wastes rich in lignocellulosic biomass have been used in the production of poly-γ-glutamic acid (γ-PGA) through separate hydrolysis and fermentation (SHF), but this process is complicated and generates a lot of wastes. In order to find a simpler and greener way to produce γ-PGA using agricultural wastes, this study attempted to establish simultaneous saccharification and fermentation (SSF) with citric acid-pretreated corn straw. The possibility of Bacillus amyloliquefaciens JX-6 using corn straw as substrate to synthesize γ-PGA was validated, and the results showed that increasing the proportion of glucose in the substrate could improve the γ-PGA yield. Based on these preliminary results, the corn straw was pretreated using citric acid. Then, the liquid fraction (xylan-rich) was used for cultivation of seed culture, and the solid fraction (glucan-rich) was used as the substrate for SSF. In a 10-L fermenter, the maximum cumulative γ-PGA concentration in batch and fed-batch SSF were 5.08 ± 0.78 g/L and 10.78 ± 0.32 g/L, respectively. Moreover, the product from SSF without γ-PGA extraction was used as a fertilizer synergist, increasing the yield of pepper by 13.46% (P < 0.05). Our study greatly simplified the production steps of γ-PGA, and each step achieved zero emission as far as possible. The SSF process for γ-PGA production provided a simple and green way for lignocellulose biorefinery and sustainable cultivation in agriculture.
富含木质纤维素生物质的农业废弃物已被用于通过分步水解和发酵（SHF）生产聚γ-谷氨酸（γ-PGA），但该过程复杂且产生大量废弃物。为了找到一种使用农业废弃物生产γ-PGA的更简单、更环保的方法，本研究尝试用柠檬酸预处理玉米秸秆建立同步糖化发酵（SSF）。验证了解淀粉芽孢杆菌JX-6以玉米秸秆为底物合成γ-PGA的可能性，结果表明增加底物中葡萄糖的比例可提高γ-PGA产量。基于这些初步结果，用柠檬酸对玉米秸秆进行预处理。然后，将液体部分（富含木聚糖）用于种子培养，将固体部分（富含葡聚糖）用作SSF的底物。在10-L发酵罐中，分批和补料分批SSF中γ-PGA的最大累积浓度分别为5.08±0.78 g/L和10.78±0.32 g/L。此外，未经γ-PGA提取的SSF产物用作肥料增效剂，使辣椒产量提高了13.46%（P<0.05）。我们的研究大大简化了γ-PGA的生产步骤，并且每个步骤都尽可能实现了零排放。γ-PGA生产的SSF工艺为木质纤维素生物精炼和农业可持续种植提供了一种简单且环保的方法。
