Brewing Of Sour Beer With Pure Saccharomyces Cerevisiae

As a kind of beer with acid taste and unique brewing style,sour beer has a broad market prospect.This study mainly optimized the process of reducing fatty acids using corn shoots as a raw material for brewing,and bred an acid-producing,ester-producing,pure brewer's yeast and an attempt to produce fermented sour beer with acid-producing and ester-producing yeasts for the production of sour beer.A new idea.The main research contents and conclusions are as follows:(1)The budding and saccharification processes were optimized for the problem of high fatty acids when the corn sprouts were raw materials for beer brewing.The optimal parameters were as follows:0.2%Ca(OH)2 was soaked at 30? for 36 h and germinated at 30? for 2 d;the macerating enzyme condition was 35? for 30 min;the corn foliar juice was passed through 8 layers.The gauze was filtered twice,centrifuged at 4000 xg for 5 min,and the upper layer was removed by 5%corn foliar juice.After optimization,the corn sprout juice prepared had a leaching rate of 73%,a reducing sugar content of 70.6 g/L,an?-amino nitrogen content of 182.72 mg/L,and a fatty acid content of 1.62 g/L.The results showed that after optimization of the process to reduce the fatty acid content,the fatty acid content has significantly decreased.(2)A lactic acid-producing recombinant strain was constructed on the above brewer's yeast.The lactate dehydrogenase gene LDH from Lactobacillus plantarum was over-expressed,and the recombinant strain BL-BYS-2 was constructed to produce 22.941 g/L lactic acid and 20.85 mg/L ethyl lactate;high-yield lactic acid and acetic acid.The recombinant strain BL-GA-BYS-2 produced 21.873 g/L lactic acid,18.689 mg/L ethyl lactate and 0.656 g/L acetic acid.The results showed that the LDH gene had a greater impact on lactic acid yield,and the LDH gene over-expressed in brewer's yeast significantly increased lactic acid content.(3)The ester-producing recombinant strain was constructed on the above brewer's yeast.Overexpression of the alcohol acyltransferase AeAT9 from kiwifruit and the propionyl-coenzyme A transferase Pctcp from Clostridium propionii,production of the highly productive ethyl acetate-producing recombinant strains B1AP-BYS-2 and B1AP-GA-BYS-2 ethyl acetate was 127.138 mg/L and 83.421 mg/L,respectively;recombinant strains B1AP-BL-BYS-2 and B1AP-BL-GA-BYS-2,and lactic acid production were 21.321 g/L and 16.589 g/L,respectively.Ethyl lactate was 14.155 mg/L and 10.863 mg/L,respectively,and ethyl acetate production was 14.249 mg/L and 11.009 mg/L,respectively.The results showed that the overexpression of AeAT9 and Pctcp genes had a great influence on the ethyl acetate content,and the ethyl acetate content increased significantly.(4)Preliminary comparison of the performance of mixed fermentation of acid-producing and ester-producing yeast.The results show that the two kinds of yeast combination fermentation can achieve the basic fermentation performance of beer,and adjust the ratio of acid and ester in acid beer according to the adjustment of acid production and ester-producing yeast ratio,and then add different proportions of yeast according to actual needs;Comparing the fermentation results of two kinds of beer brewing materials,it was found that wort was slightly higher in lactic acid content than beer,and ethyl acetate content was slightly lower,and the ethyl acetate content in the fermented wort was 27-70 mg.Between the/L,the ethyl acetate content of the fermented corn sprouts was between 50-88 mg/L;the higher alcohol content of the two raw materials was not high,the content was below 100 mg/L,and the ratio of corn shoots to juice The wort fermented with higher alcohol is slightly higher.