高产核酸的热带假丝酵母诱变选育及其发酵条件优化

以热带假丝酵母（Candida tropicalis）HY4-17为出发菌株，采用电子束辐射技术诱变，经过初筛、复筛及遗传稳定性试验选育核酸高产菌株，通过Plackett-Burman试验、最陡爬坡试验及响应面法优化培养基，并优化接种量和发酵时间以提高核酸产量。结果表明，获得一株生长快速，遗传稳定的突变菌株EBI-21，其核酸含量较出发菌株HY4-17提高了25%。最佳培养基组成为：糖蜜185 g/L，硫酸铵3 g/L，硫酸锌0.05 g/L，硫酸镁0.5 g/L，硫酸亚铁0.05 g/L，磷酸1 mL/L，pH值为4.5。在优化培养基及接种量8%，发酵时间12 h条件下，核酸产量达到1.73 g/L，较未优化前提高了80.21%，培养时间缩短了10 h。

Screening and fermentation conditions optimization of high yield nucleic acid Candida tropicalis

Using Candida tropicalis HY4-17 as a starting strain, the strain was induced by electron beam irradiation technology, and the high yield nucleic acid strain was screened by preliminary screening, secondary screening and genetic stability tests. The medium was optimized by Plackett-Burman tests, steepest ascent experiments and response surface methodology, and the inoculum and fermentation time were optimized to improve the nucleic acid production. The results indicated that the mutant strain EBI-21 with rapid growth rate and stable genetic characteristics was obtained, and the content of nucleic acid of the strain EBI-21 was increased by 25% compared with the starting strain HY4-17. The optimal medium composition was molasses 185 g/L, (NH4)2SO4 3 g/L, ZnSO4 0.05 g/L, MgSO4 0.5 g/L, FeSO4 0.05 g/L, H3PO4 1 ml/L, and pH 4.5. Under the optimal conditions of medium, with inoculum 8% and fermentation time 12 h, the nucleic acid production reached 1.73 g/L, which was 80.21% higher than that before optimization. Meanwhile, the period of incubation was 10 h shorter than that before optimization.