ILV2基因缺失对啤酒酵母生长与双乙酰代谢的影响

Effect of disrupting ILV2 gene on growth and diacetyl metabolism of brewer’s yeast

摘要:

【目的】旨在应用分子生物学方法降低啤酒发酵液中双乙酰含量，改善啤酒感官质量。【方法】以酿酒酵母S2 (Saccharomyces cerevisiae)为出发菌株，通过同源重组敲除四倍体啤酒酵母α-乙酰乳酸合成酶部分基因(ILV2)，构建缺失一个和两个ILV2等位基因的突变株QI2-1和QI2-2，并进行啤酒发酵实验。【结果】ILV2基因的缺失，会导致菌株初始生长速率的降低。其中QI2-2较为明显，12 h时，突变株与出发菌株的生长速率达到一致。啤酒发酵结果表明，与出发菌株相比，突变株QI2-1双乙酰峰值与双乙酰最终含量分别降低17.50%和17.83%，而QI2-2分别降低51.67%和45.65%。其他啤酒指标如酒精度、发酵度、残糖和风味物质等略有变化，但都在优质啤酒指标范围内，符合啤酒发酵的质量要求。【结论】通过同源重组敲除部分ILV2基因和选育低产双乙酰菌株是降低啤酒双乙酰含量、提高啤酒质量的有效方法，具有一定的实际应用价值。

Abstract:

[Objective] The purpose is to reduce diacetyl content in beer fermentation liquor by molecular biology methods and improve sensory quality of beer. [Methods] Based on S2 (Saccharomyces cerevisiae, tetraploid), mutant strains, including single ILV2 allele disruption (QI2-1) and two ILV2 alleles disruption (QI2-2) were constructed by homologous recombination to destroy acetyl lactic acid synthase gene (ILV2), and beer fermentation experiment was carried on. [Results] It could reduce?the initial growth rate of strains because of the disruption of ILV2 gene, especially QI2-2, while the growth rate of mutant strains was same as the host strain after 12 h. Beer fermentation experiment showed that ILV2 gene could reduce the production of diacetyl, and the diacetyl peak and diacetyl concentration decreased by 17.50% and 17.83% in QI2-1, 51.67% and 45.65% in QI2-2, respectively, compared with that in the host strain S2. Other indicators such as alcohol, beer fermentation degree, residual sugar and flavor changed slightly, but they were in the range of high quality beer suggested, and conformed to the requirements of the index of beer fermentation. [Conclusion] It is an effective method to reduce diacetyl content and improve the quality of beer by constructing low-diacetyl strains using homologous recombination with the disruption of Part of ILV2 gene, and it has certain actual application value.