The Study On Deletion Of Ald6 Gene In Saccharomyces Cerevisiae F

The acetic acid of beer is a important part of volatile acid and it causes beer tastes too sour when it exceed 175mg/L. The activity of aldehyde dehydrogenase of S.cerevisue controls the content of acetic acid of beer. Deletion the ald6 gene could obtain the mutant. The mutant plays a vital role in producing good quality of beer, it could be one of most effective measures to control the content of acetic acid by the utilization of the mutant. which was obtained by the method of lithium acetate transformation.A foreign gene targeting cassette was constructed from plasmid pFA6a-kanMX4 and S.cerevisue F by PCR. It consisted of a G418-resistance gene with long flanking homology regions of ald6 gene. It was transferred into the F through the procedure of intact cell transformation. It integrated into Scerevisae genome due to homologous recombination. Thus ald6 gene was disrupted and an mutant with ald6 gene knockouted was obtained.The original strain F and the ald6 gene-knockouted strain C1 differed in growth rate, fermentation property, yield of the acetaldehyde dehydrogenase, th diacetyl and the acetic acid in fermentation bottle. The latter's ability to enhance diacetyl was better than the former's. The acetic acid of the latter was lower than that of the former. The latter grew and fermented slower than the former, through continuously fermentation, the latter grew and fermented was enhanced. The acetic acid production of the gene-knockouted mutant was lower than that of the original strain in the 100 L fermentation tank, and tasted better.