Application of the Cre-loxP Recombination System for Two ILV2 Alleles Disruption in an Industrial Brewer's Yeast Strain

摘要

Diacetyl has long been considered an unpleasant off-flavor component in beer. A recombinant industrial brewer's yeast strain in which two alleles of a-acetohydroxyacid synthase (AHAS) gene (ILV2) were disrupted using the Cre-loxP recombination system was constructed to produce the lower content of diacetyl. The results showed that the diacetyl production of recombinant yeast strain S-CSL5 is always lower than that of the parental strain S-6 at all stages of beer fermentation. The total process time (from the beginning of fermentation to the diacetyl reduction is finished) of beer fermented by the recombinant strain S-CSL5 could therefore be reduced to 12 days, in contrast to 15 days required for the parental strain. The AHAS activity of S-CSL5 was lowered by 58 % compared with that of the parental strain. In addition, the real-time PCR results revealed a low expression level of ILV2 as a potential molecular determinant for low diacetyl formation.