The Study On Screening And Fermentation Technology Of Ethyl Lactate Synthesis Strains

As a result of special semi-solid fermentation of soy sauce-type liquor determines its acid,aldehydes,esters and other content are lower than the solid fermentation process liquor,resulting in soy sauce-type liquor quality is thin,the market competitiveness is not strong.Studies on the improvement of flavor substances are more concentrated on ethyl acetate,and there is relatively little research on the content of ethyl lactate.In this study,we compared the acid-producing ability of several lactic acid bacteria strains selected from the sesame-type liquor liquor,and scree ned and optimized the ester-producing ability of several producing yeast,on the basis of this,it is desirable to obtain an esterification solution having a high lactic acid content of the fermentation source by the co-culture and fermentation of the lactic acid bacteria and the ester-producing yeast and the esterification of the high-concentration lactic acid fermentation broth by ester-producing yeast,to provide more ways to improve the content of ethyl lactate in the sauce flavor liquor.The main experimental results are as follows:(1)Screening of high-yield lactic acid yeastAccording to the p H change,the Calcium dissolving ring and the lactic acid production offour kinds of lactobacillus(Lactobacillus plantarum,Lactobacillus rhamnosus,Lactobacillus fermentum andLactobacillus casei),the high-yield lactic acid strain Lactobacillus rhamnosus was screened.Through the detection ofhigh performance liquid chromatography(HPLC),the lactic acid production of Lactobacillus rhamnosus was 24.63g/L.(2)Optimizing of acid yield conditions for high-yield lactic acid lactobacillusThe conditions of lactic acid by Lactobacillus rhamnosus was optimized with the single factor and orthogonal test to optimize.The results showed that the optimal fermentation conditions for lactic acid yield was listed as follows:the initial brix was 12°Bx,inoculation amount 5%,fermentation temperature 37 ?,rotate speed 0 r/min,fermentation time 72 h,and initial pH value of medium 7.0.Through the detection of high performance liquid chromatography(HPLC),the lactic acid production was 29.01g/L,increased by 18% than before optimization.(3)Screening of high-yield ethyl lactate yeastAccording to the study of alcohol tolerance,lactic acid tolerance and ester yield for Wickerhamomyces anomalus,Saccharomyces cerevisiae,Hansenula anomala,Monascus pur pureus,Candida Antarcticaandpichia anomala,and combined with gas chromatography-mass spectrometry(GC-MC)analysis,screened the highest-yield ethyl lactate and total ester strains Wickerhamomyces anomalus.The yield of ethyl lactate and total esterwere 0.59g/L and 1.11g/L,respectively.(4)Optimizing of ester yield conditions for high-yield ethyl lactate yeastThrough the single factor and orthogonal test to optimize the conditions of ethyl lactateby Wickerhamomyces anomalus.The results showed that the favorable fermentation conditions were determined: the initial brix was 12°Bx,inoculation amount 4%,fermentation temperature 28?,rotate speed 0 r/min,the lactic acid concentration was 36g/L,the optimum fermentation time was 3d,and initial pH value of medium 4.0.In addition,through the detection of high performance liquid chromatography(HPLC),the lactic acid yield was 0.95g/L,increased by 61% than before optimization.