响应面模型分析高温蛋白酶菌株增殖和产酶关系

Effect of substrate on protease yield of thermophilic Bacillus subtilis BY25

摘要:

【目的】【方法】采用Box-Behnken法设计三因素三水平响应面实验，对比分析了高温蛋白酶高产菌株枯草芽孢杆菌BY25发酵过程中细菌生长与产酶之间的关系。【结果】实验表明，细菌生长与产酶的关系在各因素交互影响下变化显著。在中低水平的有机氮源添加条件下，细菌的大量繁殖显著抑制了蛋白酶产量，而在高水平的有机氮源添加条件下，细菌量的增长对产酶的作用由抑制转为促进。【结论】该结果表明，产酶诱导物有机氮源豆制品废渣的添加很可能显著提高了枯草芽孢杆菌群体中产酶菌的比率，而在没有合适诱导物的情况下通过增加细菌量并不能有效提高蛋白酶产量。

关键词:高温蛋白酶，菌体干重，发酵优化，Box-Behnken设计，响应曲面

Abstract:

[Objective][Methods] Box-Behnken design combing with response surface modeling was used to study the relationships between cell growth of a moderate thermophilic Bacillus subtilis BY25 and its thermostable protease yield under different carbon (glucose) and/or nitrogen (soybean waste powder) sources as well as pH values. [Results] The higher values of the coefficients of determination, lack-of-fit<4 and p value<0.05 were in good agreement with the optimum combination of process parameters, which proved the fitness of the selected model for analyzing the experimental data. Data revealed that both low and medium nitrogen applications greatly contributed to the growth of Bacillus subtilis, which however inhibited the yield of thermostable protease; under high nitrogen application both bacterial growth and protease yield were stimulated. Contour plots displayed the maximal enzyme yield was accompanied with 47.3% and 61.4% maximal biomass under low and medium nitrogen applications, but with 96.3% maximal biomass under high nitrogen application. [Conclusion] The higher nitrogen concentration could increase the specific enzyme productivity, and soybean product waste could contain a better inducer for protease synthesis in Bacillus subtilis.

Key words:Thermostable protease, Dry cell weight, Fermentation condition optimization, Box-Behnken design, Response surface