一株高温蛋白酶高产菌株产酶条件的优化

对一株高温蛋白酶高产菌株枯草芽孢杆菌BY25的发酵培养基组成与产酶条件进行了优化。正交试验结果显示培养基中各因子对产酶影响从高到低为:豆饼粉、葡萄糖、硫酸镁、麸皮、磷酸氢二钠、氯化钙。在此基础上进行培养基组成优化,将豆饼粉、麸皮混合氮源改为以豆饼粉为单一氮源进行蛋白酶发酵。单因素试验发现,在单一氮源培养条件下,培养基中各因子对产酶影响从高到低依次为:豆饼粉、葡萄糖、氯化钙、磷酸氢二钠。除微量氯化钙外,金属盐,尤其是金属硫酸盐的添加对产酶有显著抑制作用。此外,培养初始pH和培养时间对产酶有显著影响,接种量也有一定影响。通过绘制120 h产酶曲线发现,BY25产酶曲线为双峰,产酶曲线顶峰出现在发酵后72 h,优化后BY25发酵培养基各组分添加量为豆饼粉60 g/L、葡萄糖60 g/L、氯化钙 0.5 g/L、磷酸氢二钠 4 g/L,接种量为4.5%～5%,初始培养pH为8.0。优化产酶培养基和产酶条件后,发酵液酶活力可达到101.1 μmol/(min·mL)。

Optimization of fermentation medium and culture condition of a thermostable protease from moderate thermophilic strain Bacillus subtilis BY25

The fermentation media components and culture conditions of the thermostable protease from a thermophilic strain Bacillus subtilis BY25 were further studied. A six factor and three level orthogonal experiment was conducted to observe the effects of fermentation medium components on thermostable protease yield. Wheat bran was replaced by soybean cake powder for its low contribution rate. Single factor experiment was carried out to optimize the protease production. The optimized culture condition was at 30 ℃, with initiating pH of 8.0, 4.5%-5% inoculum size for 72 h; and the optimized fermentation medium components were described as follows:glucose 60 g/L, soybean cake powder 60 g/L, Na₂HPO₄ 4 g/L and CaCl₂ 0.5 g/L. After fermentation, the casein hydrolysis activity of the enzyme was estimated up to 101.1 μmol/(min·mL), much higher than other domestic reports.