微小毛霉凝乳酶基因的定点突变及突变菌株的筛选

Site-directed mutagenesis of recombinant mucor pusillus chymosin and screening of mutant strain

为了提高重组微小毛霉凝乳酶凝乳特性,对微小毛霉凝乳酶基因进行定点突变,分析了不同突变方案对凝乳活性、蛋白水解活性、酶的热稳定性的影响。以此为指标筛选到了突变体T218S菌株一株,其所产凝乳酶凝乳活力及C/P比值为52.35 U/m L和29.03,分别较改造前提高了23.2%和233.7%;非特异性水解活力由改造前的4.90 U/m L降低到1.80 U/m L,降低了63.3%。

In order to improve the curd characteristics of recombinant Mucor pusillus rennet, this study conducted site directed mutagenesis of Mucor pusillus chymosin gene and analyzed the impacts of different mutation schemes on milk clotting activity, proteolytic activity and the thermal stability. Based on the above indexes we screened mutant strain T218 S strain, whose enzyme rennet curd activity and C/P ratio reached to 52.35 U/m L and 29.03, increased by 23.2% and 233.7% respectively with that before the transformation; the non-specific hydrolysis activity decreased to 1.80 U/m L, with a decrease by 63.3% compared with 4.90 U/m L before the transformation.