School of Life Sciences, Arizona State University, Tempe, Arizona.
Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Arizona.
Biotechnol Bioeng. 2019 Dec;116(12):3476-3481. doi: 10.1002/bit.27144. Epub 2019 Aug 30.
Microbial production of fuels and chemicals from lignocellulosic biomass provides a promising alternative to conventional petroleum-derived routes. However, the heterogeneous sugar composition of lignocellulose prevents efficient microbial sugar co-fermentation due to carbon catabolite repression, which negatively affects production metrics. We previously discovered that a mutant copy of the transcriptional regulator XylR (P363S and R121C; denoted as XylR*) in Escherichia coli has a higher DNA-binding affinity than wild-type XylR, leading to a stronger activation of the d-xylose catabolic genes and a release from glucose-induced repression on xylose fermentation. Here, we showed that XylR* also releases l-arabinose-induced repression on xylose fermentation through altered transcriptional control, enhancing co-fermentation of arabinose-xylose sugar mixtures in wild-type E. coli. Integrating xylR* into an ethanologenic E. coli resulted in the coutilization of 96% of the provided glucose-xylose-arabinose mixtures (120 g/L total sugars supplied) with an ethanol yield higher than 90% of the theoretical maximum by simple batch fermentations.
从木质纤维素生物质生产燃料和化学品为传统的石油衍生途径提供了一种有前途的替代方法。然而，木质纤维素的不均匀糖组成由于碳分解代谢物抑制而阻止了有效的微生物糖共发酵，这对生产指标产生了负面影响。我们之前发现，转录调节因子 XylR 的突变拷贝（P363S 和 R121C；表示为 XylR*）在大肠杆菌中具有比野生型 XylR 更高的 DNA 结合亲和力，导致 d-木糖分解代谢基因的更强激活，并从葡萄糖诱导的木糖发酵抑制中释放出来。在这里，我们表明 XylR也通过改变转录控制释放木糖发酵中阿拉伯糖诱导的抑制作用，从而增强了阿拉伯糖-木糖糖混合物在野生型大肠杆菌中的共发酵。将 xylR整合到乙醇生成大肠杆菌中，导致在简单分批发酵中，对提供的葡萄糖-木糖-阿拉伯糖混合物（120g/L 总糖供应）的 96%进行了有效利用，乙醇产率高于理论最大值的 90%。
