产低温蛋白酶酵母菌株的筛选及发酵培养基优化

该研究从新疆本地分离获得的200株酵母菌中筛选产低温蛋白酶的菌株，并通过形态观察、生理生化试验及分子生物学方法 对菌株WLY1、WLY2和MLY1进行鉴定，最后通过响应面法对20 ℃条件下蛋白酶活力高的菌株的发酵培养基配方优化。 结果表明， 共筛选到14株产低温蛋白酶菌株，其中3株（WLY1、WLY2和MLY1）于20 ℃条件下仍具有较强的产低温蛋白酶能力，其蛋白酶酶活 力依次为69.03 U/mL、34.20 U/mL、29.70 U/mL；鉴定菌株WLY1、WLY2和MLY1分别为双倒卵形红冬孢酵母（Rhodosporidium diobo- vatum）、Cryptococcus adeliensis、Barnettozyma californica；其中菌株WLY1产低温蛋白酶能力强，且其最佳产蛋白酶培养基配方为酵 母浸粉1.64%、蛋白胨1.21%、干酪素1.48%。在此最优条件下，菌株WLY1的蛋白酶活力达到251.51U/mL，约为优化前的4倍，同比其 他产蛋白酶功能菌具有较大的工业应用潜力。

Screening of low-temperature protease-producing yeast and optimization of fermentation medium

The low-temperature protease-producing strains were screened from 200 yeasts isolated from Xinjiang, strains WLY1, WLY2 and MLY1 were identified by morphological observation, physiological and biochemical tests and molecular biotechnology. The fermentation medium formula of strains with high protease activity at 20 ℃ was optimized by response surface methodology. The results showed that a total of 14 strains producing low-temperature protease were screened out, among them, the protease activities of yeasts WLY1, WLY2 and MLY1 which had strong ability to pro- duce low-temperature protease at 20 ℃ were 69.03 U/ml, 34.20 U/ml and 29.70 U/ml, respectively. Strains WLY1, WLY2 and MLY1 were identified as Rhodosporidium diobovatum, Cryptococcus adeliensis and Barnettozyma californica, respectively. The strain WLY1 had high yield low-tempera-ture protease and the optimal fermentation medium formula of which was determined as follows: yeast extract powder 1.64%, peptone 1.21%, casein 1.48%. Under the optimal conditions, the protease activity of strain WLY1 reached 251.51 U/ml, which was about 4 times that of before optimization. Compared with other functional yeasts with protease yield, the strain WLY1 had greater industrial application potential.