凉州熏醋酿造过程产乙偶姻酵母菌筛选及其发酵培养基优化

Isolation of yeast with high acetoin- producing ability from Liangzhou fumigated vinegar and optimization for its fermentation medium

乙偶姻是凉州熏醋特征风味成分四甲基吡嗪的前体。本实验从凉州熏醋发酵料醅中分离获得了一株产乙偶姻酵母菌T8,通过经典鉴定方法结合ITS基因测序的方法,确定其为葡萄汁有孢汉逊酵母(Hanseniaspora uvarum)。为探明T8菌株生长及代谢产乙偶姻的营养需求,本实验对产乙偶姻酵母菌T8发酵培养基进行了优化,以期为传统食醋酿造工艺现代化改造过程中人工接种增香酵母种子的制备提供培养基。通过研究不同碳源、氮源、无机盐对T8菌株产乙偶姻的影响,确定了发酵培养基的最终组分:葡萄糖60 g/L,蛋白胨10 g/L,酵母膏10 g/L,(NH_4)_2HPO_48 g/L,KH_2PO_40.5 g/L,Mg SO_4·7H_2O 0.75 g/L,Mn SO_40.6 g/L。培养基优化后,乙偶姻产量达到15.236 g/L,与初始发酵培养基相比提高了20.65%。人工接种T8菌株种子液所酿食醋中四甲基吡嗪的含量较对照提高了22.1%,增香效果明显,证明H.Uvarum T8菌株可以作为食醋酿造的增香酵母。

Acetoin,a precursor of tetramethylpyrazine, is identified as a flavor component of Liangzhou fumigated vinegar.in the test, an acetoin-producing strainT8 was isolated from the fermented cultures of Liangzhou fumigated vinegar,which was identified as Hanseniaspora uvarum by classical identification methods and ITS gene sequence similarities. In order to further know the nutritional requirements of T8 growth and metabolism, the fermentation medium for producing acetoin with T8 was optimized,so that it could provide the better seed medium for flavoring yeast in modern vinegar brewing process.The key fermentation factors of affecting acetoin yield by H. uvarum were studied, including the carbon resource, the nitrogen resource, inorganic salts concentration. The results showed that the best fermentation medium component was：glucose 60 g/L, peptone 10 g/L, yeast extract 10 g/L, （ NH4 ）2HPO4 8 g/L, KH2PO4 0.5 g/L, MgSO4 , 7H2O 025 g/L, MnSO4 0.6 g/L. Under the optimized conditions,the acetoin yield reached 15.236 g/L, which was increased by 20.65% in comparison with the initial fermentation medium, and the content of tetramethylpyrazine in vinegar cultures was increased by 22.1% in comparison with control in the artificial inoculation vinegar brewing test,it showed that T8 could help to improve the vinegar flavor.