Jo Jung-Hyun, Oh Sun-Young, Lee Hyeun-Soo, Park Yong-Cheol, Seo Jin-Ho
Department of Agricultural Biotechnology and Center for Food and Bioconvergence, Seoul National University, Seoul, Republic of Korea.
Department of Bio and Fermentation Convergence Technology, Kookmin University, Seoul, Republic of Korea.
Biotechnol J. 2015 Dec;10(12):1935-43. doi: 10.1002/biot.201500068. Epub 2015 Nov 11.
Xylitol, a natural sweetener, can be produced by hydrogenation of xylose in hemicelluloses. In microbial processes, utilization of only NADPH cofactor limited commercialization of xylitol biosynthesis. To overcome this drawback, Saccharomyces cerevisiae D452-2 was engineered to express two types of xylose reductase (XR) with either NADPH-dependence or NADH-preference. Engineered S. cerevisiae DWM expressing both the XRs exhibited higher xylitol productivity than the yeast strain expressing NADPH-dependent XR only (DWW) in both batch and glucose-limited fed-batch cultures. Furthermore, the coexpression of S. cerevisiae ZWF1 and ACS1 genes in the DWM strain increased intracellular concentrations of NADPH and NADH and improved maximum xylitol productivity by 17%, relative to that for the DWM strain. Finally, the optimized fed-batch fermentation of S. cerevisiae DWM-ZWF1-ACS1 resulted in 196.2 g/L xylitol concentration, 4.27 g/L h productivity and almost the theoretical yield. Expression of the two types of XR utilizing both NADPH and NADH is a promising strategy to meet the industrial demands for microbial xylitol production.
木糖醇是一种天然甜味剂，可通过半纤维素中木糖的氢化反应制得。在微生物过程中，仅利用NADPH辅因子限制了木糖醇生物合成的商业化。为克服这一缺点，对酿酒酵母D452-2进行了工程改造，使其表达两种具有NADPH依赖性或NADH偏好性的木糖还原酶（XR）。在分批培养和葡萄糖限制补料分批培养中，同时表达这两种XR的工程酿酒酵母DWM比仅表达NADPH依赖性XR的酵母菌株（DWW）表现出更高的木糖醇生产率。此外，在DWM菌株中共表达酿酒酵母ZWF1和ACS1基因可提高细胞内NADPH和NADH的浓度，相对于DWM菌株，最大木糖醇生产率提高了17%。最后，酿酒酵母DWM-ZWF1-ACS1的优化补料分批发酵产生了196.2 g/L的木糖醇浓度、4.27 g/（L·h）的生产率以及几乎理论产量。利用NADPH和NADH的两种XR的表达是满足微生物木糖醇生产工业需求的一种有前景的策略。
