絮凝基因FLO1及FLO1c高表达提高工业酿酒酵母乙酸耐受性及发酵性能

Improvement of acetic acid tolerance and fermentation performance of industrial Saccharomyces cerevisiae by overexpression of flocculent gene FLO1 and FLO1c

摘要:

乙酸是生物质乙醇发酵过程中酵母细胞面临的重要抑制剂之一，对细胞生长及发酵性能有强烈的抑制作用。增强酵母菌对乙酸胁迫的耐受性对提高乙醇产率具有重要意义。用分别带有完整絮凝基因FLO1及其重复序列单元C发生缺失的衍生基因FLO1c的重组表达质粒分别转化非絮凝型工业酿酒酵母CE6，获得絮凝型重组酵母菌株6-AF1和6-AF1c。同时以空载体pYCPGA1转化CE6的菌株CE6-V为对照菌株。与CE6-V相比，絮凝酵母明显提高了对乙酸胁迫的耐受性。在0.6% (V/V) 乙酸胁迫下，6-AF1和6-AF1c的乙醇产率分别为对照菌株CE6-V的1.56倍和1.62倍；在1.0% (V/V) 乙酸胁迫下，6-AF1和6-AF1c的乙醇产率分别为对照菌株CE6-V的1.21倍和1.78倍。可见絮凝能力改造能明显提高工业酿酒酵母的乙酸胁迫耐受性及发酵性能，而且FLO1内重复序列单元C缺失具有更加明显的效果。

Abstract:

Flocculent gene FLO1 and its truncated form FLO1c with complete deletion of repeat unit C were expressed in a non-flocculent industrial strain Saccharomyces cerevisiae CE6 to generate recombinant flocculent strains 6-AF1 and 6-AF1c respectively. Both strains of 6-AF1 and 6-AF1c displayed strong flocculation and better cell growth than the control strain CE6-V carrying the empty vector under acetic acid stress. Moreover, the flocculent strains converted glucose to ethanol at much higher rates than the control strain CE6-V under acetic acid stress. In the presence of 0.6% (V/V) acetic acid, the average ethanol production rates of 6-AF1 and 6-AF1c were 1.56 and 1.62 times of that of strain CE6-V, while the ethanol production rates of 6-AF1 and 6-AF1c were 1.21 and 1.78 times of that of strain CE6-V under 1.0% acetic acid stress. Results in this study indicate that acetic acid tolerance and fermentation performance of industrial S. cerevisiae under acetic acid stress can be improved largely by flocculation endowed by expression of flocculent genes, especially FLO1c.