为提高食醋风味,该研究采用透明圈法及高效液相色谱(HPLC)法从麸醋醋醅中分离筛选既产酸又产蛋白酶的菌株,采用形态学观察及分子生物学技术进行鉴定,对菌株安全性、最适生长条件及产蛋白酶条件进行考察,并将其应用于固态发酵食醋.结果表明,筛选出一株既产酸又产蛋白酶的菌株(编号为D-6),将其鉴定为表皮葡萄球菌(Staphylococcus epidermidis),无致病性;最适生长条件为培养温度37℃,pH 5.5,乙醇体积分数0.5%,葡萄糖含量3%;最佳产蛋白酶条件为:培养温度36℃,接种量4%,培养时间41 h.在此优化条件下,蛋白酶活性为36.12 U/g,与优化前相比提高了49.25%;将其应用于固态发酵食醋,总酸、氨基酸态氮、乙酸及乳酸含量均增加,其含量分别为0.95 mmol/10 g、0.21 g/100 g、182.2 mg/L、1 472.6 mg/L.
In order to improve vinegar flavor,the both acid-and protease-producing strain was separated and screened from the Cupei of bran vinegar by transparent circle method and HPLC.The strain was identified by morphological observation and molecular biology technique,the safety,optimal growth conditions and protease production conditions were investigated,and the strains were applied to solid-state fermented vinegar.The results showed that a strain produced both acid and protease was selected(numbered as D-6),identified as Staphylococcus epidermidis,without pathogenicity.The optimal growth conditions were as follows:culture temperature 37 ℃,pH 5.5,ethanol volume fraction 0.5%,glucose content 3%.The optimum conditions for protease production were as follows:culture temperature 36 ℃,inoculum 4%,culture time 41 h.Under the optimized conditions,the protease activity was 36.12 U/g,which was 49.25%%higher than that before optimization.When it was applied to solid-state fermented vinegar,the contents of total acid,amino acid nitrogen,acetic acid and lactic acid were increased,and the contents were 0.95 mmol/10 g,0.21 g/100 g,182.2 mg/L,and 1 472.6 mg/L,respectively.