角质酶产生菌Thermobifida fusca WSH03-11诱变及高产突变株发酵条件优化

以Thermobifida fusca WSH03-11为出发菌株，经硫酸二乙酯诱变，获得一株遗传稳定性好的高产角质酶的突变菌株(酶活由2.3 U/mL提高为8.9 U/mL)。确定了以乙酸钠为碳源，并在2.5 L发酵罐中研究了不同pH值对突变株角质酶分批发酵的影响。根据不同pH值下发酵过程中细胞比生长速率及产物比生长速率的变化，确定了分阶段控制pH值的策略，即在发酵前20 h控制pH值7.3、20 h后控制pH值7.6，这种条件下角质酶活达到19.8 U/mL，比采用单一pH值7.0、7.3、7.6、7.9下的最大值分别提高了125%，64%，37%，47%。

Mutagenesis of cutinase-producing strain Thermobifida fusca WSH03-11 and optimization of fermentation conditions of mutant with high cutinase production

Thermobifida fusca WSH03-11 was mutagenized by using DES and a mutant was isolated after three runs of screening. The cutinase activity was improved from 2.3 U/mL to 8.9 U/mL. After sodium acetate was selected as fermentation carbon source,batch microbial cutinase fermentation by a mutant of Thermobifida fusca WSH03-11 at various pH values ranging from 7.0 to 7.9 was studied. Based on time courses of the specific cell growth rate and specific cutinase formation rate at different pH values,a two-stage pH value-shift strategy in which pH value was controlled at 7.3 in the first 20 h,and then switched to 7.6 after 20 h was developed. By applying this pH value-shift strategy in cutinase fermentation,the maximal cutinase activity reached 19.8 U/mL and was increased by 125%,64%,37% and 47%,compared to those with constant pH values at 7.0,7.3,7.6 and 7.9,respectively.