微生物发酵高温豆粕制备大豆肽具有生产成本低、水解度高的特点。该研究以酶活力为指标,通过紫外诱变和遗传稳定性试验选育出遗传性能稳定的蛋白酶高产菌株;以水解度为监测指标,采用该菌株发酵挤压膨化的高温豆粕,优化发酵工艺条件。紫外诱变条件为20 W紫外灯35 cm处辐照4 min;采用单因素和L9(34)正交试验设计进行培养基组成的优化:可溶性淀粉2.5%、MgSO40.04%、豆粕10%、吐温-80 0.5%;采用单因素试验方法确定的培养条件为:温度30℃、时间44 h、接种量4%、菌龄21 h、摇床速度200 r/min、装液量30 mL/250 mL、起始pH 7.5,此条件下高温豆粕的水解度可达到22.86%,比优化前提高了8.34%。

The soybean polypeptides prepared by microbial fermentation of high-temperature soybean meal have characteristic of low production cost and high hydrolysis.Using enzyme activity as index,high-yield proteinase producing strain was screened by UV mutagenesis and genetic stability test in this study.Using hydrolysis degree as surveillance index,the strain was used to ferment extrusion and expansion of high-temperature soybean meal,and the fermentation process was optimized.The conditions of UV mutagenesis were as follows: UV watt was 20,irradiant distance was 35cm,irradiant time was 4min.Optimation of medium was performed by single factor and L_9(3~4) orthogonal experiments.The composition of optimal medium was as follows: soluble starch 2.5%,magnesium sulfate 0.04%,soybean meal 10% and Tween-80 0.5%.The cultural condition determined by single factor experiment was as follows: temperature 30℃ for 44 h,inoculum 4%,culture-age 21 h,agitation 200r/min,medium volume 30 mL/250 mL,initial pH 7.5.Using the described optimum medium and condition,hydrolysis degree of high-temperature soybean meal could reach 22.86% which was 8.34% higher than before.