School of Chemistry and Chemical Engineering, Hefei Normal University, Hefei 230601, China.
College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China.
Molecules. 2023 Feb 6;28(4):1550. doi: 10.3390/molecules28041550.
Before fermentation with hemicellulosic hydrolysate as a substrate, it is generally necessary to detoxify the toxic substances that are harmful to microorganism growth. Cyclic AMP receptor protein (CRP) is a global regulator, and mutation of its key sites may have an important impact on virulence tolerance. Using corncob hydrolysate without ion-exchange or lime detoxification as the substrate, shake flask fermentation experiments showed that CRP mutant IS5-dG (I112L, T127G, A144T) produced 18.4 g/L of xylitol within 34 h, and the OD was 9.7 at 24 h; these values were 41.5% and 21.3% higher than those of the starting strain, IS5-d, respectively. This mutant produced 82 g/L of xylitol from corncob hydrolysate without ion-exchange or lime detoxification during fed-batch fermentation in a 15-L bioreactor, with a productivity of 1.04 g/L/h; these values were 173% and 174% higher than the starting strain, respectively. To our knowledge, this is the highest xylitol concentration and productivity produced by microbial fermentation using completely non-detoxified hemicellulosic hydrolysate as the substrate to date. This study also showed that alkali neutralization, high temperature sterilization, and fermentation of the hydrolysate had important effects on the xylose loss rate and xylitol production.
在使用半纤维素水解物作为底物进行发酵之前，通常需要对可能危害微生物生长的有毒物质进行解毒。环磷酸腺苷受体蛋白（CRP）是一种全局调节剂，其关键位点的突变可能对毒力耐受性产生重要影响。使用未经离子交换或石灰解毒的玉米芯水解物作为底物，摇瓶发酵实验表明，CRP 突变体 IS5-dG（I112L、T127G、A144T）在 34 小时内产生了 18.4 g/L 的木糖醇，24 小时时 OD 值为 9.7；与出发菌株 IS5-d 相比，这两个值分别提高了 41.5%和 21.3%。该突变体在 15-L 生物反应器中进行分批补料发酵时，从未经离子交换或石灰解毒的玉米芯水解物中生产了 82 g/L 的木糖醇，比生产能力为 1.04 g/L/h；与出发菌株相比，这两个值分别提高了 173%和 174%。据我们所知，这是迄今为止使用完全未经解毒的半纤维素水解物作为底物进行微生物发酵生产的最高木糖醇浓度和生产能力。本研究还表明，碱中和、高温灭菌和水解物发酵对半乳糖损失率和木糖醇生产有重要影响。
