高糖化力白曲霉的复合诱变及固态发酵条件优化

采用紫外线及常压室温等离子体（ARTP）复合诱变技术对白曲霉（Aspergillus candidus）Nz 3.602进行诱变选育。对诱变致死率进行测定，确定最佳诱变条件为：15 W紫外灯照射12 min，ARTP处理40 s。对突变菌株进行透明圈法初筛、糖化力测定法复筛，最终得到产酶能力较高的突变菌株B5。其糖化酶酶活为1 050.32 U/g，较出发菌株糖化酶酶活提高85.53%，并且遗传稳定性较好。以菌株B5为研究对象，经单因素试验和响应面分析法对其固态发酵条件进行优化，最佳固态发酵条件为：糠壳添加量15%，原料含水量70%，接种量12%，培养时间5 d，培养温度30 ℃。该条件下糖化酶酶活为（1 254.17±6.14） U/g，比优化前提高了19.41%。

Compound mutagenesis of high saccharifying Aspergillus candidus and optimization ofsolid-state fermentation conditions

Aspergillus candidus Nz 3.602, a starting strain, was mutated by ultraviolet (UV) and atmospheric and room temperature plasma (ARTP). According to the lethality of mutagenesis, the optimal mutagenesis conditions were determined as follows: ultraviolet irradiation for 12 min and ARTP treatment for 40 s. The mutant strains were screened by the transparent circle method and re-screened by determining saccharification power, and finally the mutant strain B5 with higher enzyme production capacity was obtained. The saccharification enzyme activity of the strain B5 was 1 050.32 U/g, which was 85.53% higher than that of the starting strain, and the genetic stability was better. The solid-state fermentation conditions of the strain B5 were optimized by single factor tests and response surface methodology, and the optimal solid-state fermentation conditions were determined as follows: bran shell 15%, moisture 70%, inoculum 12%, cultivation time 5 d and temperature 30 ℃. Under the optimal conditions, the saccharifying enzyme activity could reach (1 254.17±6.14) U/g, which was 19.41% higher than that of before optimization.