Abstract Furfural is a major toxic byproduct present in the hydrolysate of lignocellulosic biomass, which inhibits the growth and ethanol fermentation of Saccharomyces cerevisiae. To enhance yeast tolerance to furfural, extracellular redox potential (ORP) regulation was employed for the fermentation system through controlling ORP at −150 mV, −100 mV and −50 mV, respectively, by adjusting its aeration. When ORP was controlled at −100 mV, yeast cells exhibited improved growth, furfural degradation and ethanol production. Analysis of intracellular redox pairs such as NADH/NAD+ and GSH/GSSG indicated a correlation between extracellular ORP and intracellular redox homeostasis. Moreover, intracellular reactive oxygen species (ROS) caused by furfural stress decreased under the redox control condition, which consequently conferred yeast cells tolerance to furfural. Comparative transcriptome analysis for yeast cells sampling under the ORP control at −100 mV further revealed that the expression of genes for proliferation was up-regulated to degrade furfural more efficiently. These results demonstrated that extracellular ORP regulation would be a strategy for enhancing yeast tolerance to furfural stress during cellulosic ethanol fermentation.

中文翻译：

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细胞外氧化还原电位调节提高酵母对糠醛的耐受性

摘要 糠醛是木质纤维素生物质水解产物中存在的主要有毒副产物，可抑制酿酒酵母的生长和乙醇发酵。为了提高酵母对糠醛的耐受性，发酵系统采用细胞外氧化还原电位 (ORP) 调节，通过调节曝气将 ORP 分别控制在 -150 mV、-100 mV 和 -50 mV。当 ORP 控制在 -100 mV 时，酵母细胞表现出更好的生长、糠醛降解和乙醇生产。对细胞内氧化还原对（如 NADH/NAD+ 和 GSH/GSSG）的分析表明细胞外 ORP 与细胞内氧化还原稳态之间存在相关性。此外，在氧化还原控制条件下，由糠醛应激引起的细胞内活性氧（ROS）减少，因此赋予酵母细胞对糠醛的耐受性。在-100 mV ORP 控制下采样的酵母细胞的比较转录组分析进一步表明，增殖基因的表达被上调以更有效地降解糠醛。这些结果表明，细胞外 ORP 调节将是在纤维素乙醇发酵过程中增强酵母对糠醛胁迫耐受性的一种策略。