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

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.