School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China.
State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640, China.
Appl Microbiol Biotechnol. 2020 Jun;104(12):5605-5617. doi: 10.1007/s00253-020-10554-7. Epub 2020 Apr 4.
The redox-sensing transcriptional repressor Rex (Rex) displayed diverse functions in different microbial species. Nowadays, only part function of rex has been verified in vitro and alcohol dehydrogenase gene (adhE) as the target of Rex has been widely reported. In this study, rex was knocked out in Thermoanaerobacterium aotearoense SCUT27 (GDMCC 60765) and the carbon metabolic distribution analysis was performed. Results showed that the ethanol yield (mol product/mol carbon) of SCUT27(Δrex) had increased by 75.00-90.91%, cell growth improved by 27.27-36.36%, and acetic acid and lactic acid decreased by 58.33-61.54% accompanied with the yield of hydrogen decreased by 46.15-58.35% within different carbon sources. The ability of sugar consumption of SCUT27(Δrex) had improved about 74.19-130.55% with the improvement of total ATP concentration and the cofactors NADH and NAD concentrations. In addition, the specific activities of alcohol dehydrogenase of SCUT27(Δrex) with NADH and NADPH as cofactors were improved by 119.26-140.28% and 35.66-47.69%, respectively. After ldh was further knocked out in SCUT27(Δrex), SCUT27(ΔldhΔrex) showed higher ethanol production and yield when various carbon resources were used as substrates (including glucose, xylose, glucose/xylose mixture and three kinds of lignocellulosic hydrolysates). This study confirms that Rex is an important regulator for determining products distribution in SCUT27 and deletion of rex and ldh is a promising strategy for enhanced ethanol production.
氧化还原敏感转录抑制因子 Rex（Rex）在不同微生物物种中表现出多种功能。如今，仅部分 Rex 功能已在体外得到验证，并且广泛报道了以醇脱氢酶基因（adhE）为靶标的 Rex。在这项研究中，敲除了Thermoanaerobacterium aotearoense SCUT27（GDMCC 60765）中的 rex，并进行了碳代谢分布分析。结果表明，与野生型相比，在不同碳源中，SCUT27（Δrex）的乙醇产率（mol 产物/mol 碳）提高了 75.00-90.91%，细胞生长提高了 27.27-36.36%，乙酸和乳酸分别降低了 58.33-61.54%，氢气产率降低了 46.15-58.35%。SCUT27（Δrex）利用糖的能力提高了约 74.19-130.55%，这伴随着总 ATP 浓度以及辅助因子 NADH 和 NAD 浓度的提高。此外，以 NADH 和 NADPH 为辅助因子时，SCUT27（Δrex）的醇脱氢酶比活分别提高了 119.26-140.28%和 35.66-47.69%。在进一步敲除 ldh 后，当以各种碳源（包括葡萄糖、木糖、葡萄糖/木糖混合物和三种木质纤维素水解物）作为底物时，SCUT27（ΔldhΔrex）表现出更高的乙醇产量和产率。本研究证实 Rex 是决定 SCUT27 产物分布的重要调控因子，敲除 rex 和 ldh 是提高乙醇产量的一种有前途的策略。
