Abstract:

Fuel ethanol production using renewable cellulosic materials has attracted widespread attention by researchers. However, acetic acid released from the pretreatment process exerts severe inhibition on yeast cell growth and ethanol fermentation. Therefore, improvement of acid tolerance of industrial Saccharomyces cerevisiae benefits efficient cellulosic ethanol production. In this work, glutaredoxin encoding gene GRX5 was overexpressed in S. cerevisiae, and it was found that the GRX5 overexpression strain grew better than that of the control strain in the plates containing 5 g·L^-1 acetic acid. When ethanol fermentation in the presence of 5 g·L^-1 acetic acid was evaluated, it was found that the GRX5 overexpression strain consumed all glucose in the broth within 48 h, 12 h shorter than that of the control strain. Ethanol productivity of the GRX5 overexpressed strain was determined to be 0.897 g·L^-1·h^-1, with a 28.5% increase than that of the control strain. Analysis of the key metabolites showed that the GRX5 overexpression strain produced higher concentration of trehalose and glycerol, which might explain its improved cell viability in the presence of acetic acid stress.

Key words: glutaredoxin, GRX5, fuel ethanol, fermentation efficiency, acetic acid stress, Saccharomyces cerevisiae

摘要：

利用可再生的纤维素原料生产燃料乙醇是国内外研究的热点。但纤维素原料一些预处理过程产生的乙酸对酿酒酵母细胞生长和乙醇发酵产生强烈抑制,因此,提高酿酒酵母细胞的乙酸耐受性是提高纤维素乙醇发酵效率的重要手段。本文研究了谷氧还蛋白家族中GRX5p的编码基因的过表达对酿酒酵母在乙酸胁迫条件下细胞生长和发酵性能的影响。结果表明,过表达GRX5的重组菌株在含有5 g·L^-1乙酸的平板中生长优于对照菌株;在含有5 g·L^-1乙酸的培养基中进行乙醇发酵,过表达GRX5的重组菌株可在48 h基本消耗培养基中所有的葡萄糖,发酵周期比对照菌株缩短了12 h。过表达GRX5菌株的乙醇生产强度为0.897 g·L^-1·h^-1,比对照提高了28.5%。代谢物分析结果表明,过表达GRX5的重组菌株可产生更多的保护性物质海藻糖和甘油,有利于增强菌株胁迫耐受性。

关键词: 谷氧还蛋白, GRX5, 燃料乙醇, 发酵效率, 乙酸胁迫, 酿酒酵母