Department of Biotechnology, Graduate School, Korea University, Seoul, Korea.
School of Food Science and Biotechnology, Kyungpook National University, Daegu, Korea.
Appl Microbiol Biotechnol. 2019 Jul;103(13):5435-5446. doi: 10.1007/s00253-019-09829-5. Epub 2019 Apr 19.
Bioconversion of lignocellulosic biomass into ethanol requires efficient xylose fermentation. Previously, we developed an engineered Saccharomyces cerevisiae strain, named SR8, through rational and inverse metabolic engineering strategies, thereby improving its xylose fermentation and ethanol production. However, its fermentation characteristics have not yet been fully evaluated. In this study, we investigated the xylose fermentation and metabolic profiles for ethanol production in the SR8 strain compared with native Scheffersomyces stipitis. The SR8 strain showed a higher maximum ethanol titer and xylose consumption rate when cultured with a high concentration of xylose, mixed sugars, and under anaerobic conditions than Sch. stipitis. However, its ethanol productivity was less on 40 g/L xylose as the sole carbon source, mainly due to the formation of xylitol and glycerol. Global metabolite profiling indicated different intracellular production rates of xylulose and glycerol-3-phosphate in the two strains. In addition, compared with Sch. stipitis, SR8 had increased abundances of metabolites from sugar metabolism and decreased abundances of metabolites from energy metabolism and free fatty acids. These results provide insights into how to control and balance redox cofactors for the production of fuels and chemicals from xylose by the engineered S. cerevisiae.
木质纤维素生物质转化为乙醇需要高效的木糖发酵。先前，我们通过合理和反向代谢工程策略开发了一种工程酿酒酵母菌株，命名为 SR8，从而提高了其木糖发酵和乙醇生产能力。然而，其发酵特性尚未得到充分评估。在这项研究中，我们研究了 SR8 菌株与天然产朊假丝酵母相比，在木糖、混合糖和厌氧条件下的乙醇生产中的木糖发酵和代谢谱。与 Sch. stipitis 相比，SR8 菌株在高浓度木糖、混合糖和厌氧条件下培养时，具有更高的最大乙醇浓度和木糖消耗率。然而，当以 40 g/L 木糖作为唯一碳源时，其乙醇生产率较低，主要是由于木糖醇和甘油的形成。全局代谢物分析表明，两株菌的木酮糖和甘油-3-磷酸的细胞内产生率不同。此外，与 Sch. stipitis 相比，SR8 菌株中来自糖代谢的代谢物丰度增加，而来自能量代谢和游离脂肪酸的代谢物丰度降低。这些结果为如何控制和平衡氧化还原辅因子提供了深入的了解，从而通过工程化酿酒酵母从木糖生产燃料和化学品。
