Abstract

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.

中文翻译：

---

氧化还原敏感的转录阻遏物Rex对于调节嗜热厌氧杆菌SCUT27中的产物分布非常重要。

摘要

氧化还原敏感的转录阻遏物雷克斯（Rex）在不同的微生物物种中表现出多种功能。如今，rex的部分功能已在体外得到验证，并且酒精脱氢酶基因（adhE）作为Rex的靶标已被广泛报道。在这项研究中，雷克斯在嗜热厌氧性厌氧杆菌SCUT27（GDMCC 60765）中被敲除，并进行了碳代谢分布分析。结果表明，乙醇产率（摩尔产物/摩尔碳）SCUT27的（Δ雷克斯）增加了75.00–90.91％，细胞生长改善了27.27–36.36％，乙酸和乳酸减少了58.33–61.54％，同时在不同碳源下氢气的产量减少了46.15–58.35％。SCUT27（Δ的糖消耗能力雷克斯）与总ATP浓度的提高和辅因子NADH和NAD约74.19-130.55％提高⁺浓度。此外，醇的具体活动脱氢酶SCUT27的（Δ雷克斯）与NADH和NADPH作辅因子分别通过119.26-140.28％和35.66-47.69％，改善。后的ldh进一步在SCUT27（Δ敲除雷克斯），SCUT27（Δ LDH Δ雷克斯）在使用多种碳资源作为底物（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产物）时显示出更高的乙醇产量和产率。这项研究证实，Rex是确定SCUT27中产品分布的重要调节剂，而rex和ldh的缺失是提高乙醇产量的有前途的策略。