Construction Of Saccharomyces Cerevisiae Strain With High Yield Of Ethyl Lactate

Less ethyl lactate in Chinese Baijiu will lead to a thin body,light taste.Due to the strictly controlled sanitary conditions of the modem large winery,species of fermentation medium were single,resulting in low content of ethyl lactate,also,the quality of Baijiuwas not high.It has been reported that Candida antarctica lipase B(CalB)played an important role in increasing the content of ethyl lactate in Baijiu.In this paper,different methods to express lipase B of Candida antarctica were used to improve the content of ethyl lactate in Chinese Baijiu.The main research contents are as follows:(1)Saccharomyces cerevisiae rDNA was used as exogenous gene integration site to construct multi-copy integrated strain to expression CalB.The parental strains,single-copy strains,multi-copy strains were validated by Fenjiu semi-solid fermentation.After 6 days of fermentation,the main flavors were determined by steaming wine.The yield of ethyl lactate of parental strainsa5 was 114.00 mg/L.That of single copy strain nsB was 178.30 mg/L.The yield of ethyl lactate of multi-copy strain ?BAT2-n3 reached 223.16 mg/L,which increased by 95.75%compared to the parent strain,and increased by 25.16%compared with the single copy strain.And ethyl acetate production of multi-copy strains also increased,the highest of which increase of 21.20%.(2)We also constructed a type lectin surface display strains.The yield of ethyl lactate ofa5was 204.30 mg/L,and the ethyl lactate yield of single copy strain nsB and INU were 324.40 mg/L and 325.63 mg/L,as measured by the Fenjiu semi-solid fermentation.The yield of ethyl lactate of a-type lectin surface display strain was up to 247.42 mg/L,which was 21.11%higher than that of the parent strain,but not as high as that of the single copy strain.(3)The a-type lectin surface display vector Yep-PCAK was constructed to build a-type lectin surface display strain.The yield of ethyl lactate of the parent straina5 was 120.8 mg/L after the semi-solid fermentation of the fragrance liquor.The amount of ethyl lactate produced by the single-copy strain INU and nsB were 220.7 mg/L and 208.3 mg/L respectively.The highest yield of ethyl lactate ina-agglutinin surface-displayed strains was 212.6 mg/L,produced by Ca-2.The results show,compared with the parent strain,the most improved strain was rDNA multicopy expression of Candida antartica lipase B.It could not only improve the content of ethyl lactate in white wine,but also increase the content of ethyl acetate accordingly.It plays a nonnegligible role in enriching the taste of liquor and enhancing the quality of liquor.