罗汉果内生菌中乙醇降解菌株的筛选及其发酵条件优化

通过传统培养分离法从广西龙胜县的罗汉果植株中分离内生菌，通过乙醇耐受性测定和重铬酸钾-硫酸法从中筛选出对乙醇具有降解活性的菌株，通过形态观察及分子生物学技术对其进行鉴定，并以乙醇降解率为评价指标，采用单因素试验及正交试验对其发酵条件进行优化。结果表明，从罗汉果中分离得到68株内生菌，从中筛选到1株乙醇降解活性较高的菌株G-1，并被鉴定为尖孢镰刀菌（Fusarium oxysporum），其降解乙醇的最优发酵条件为马铃薯葡萄糖琼脂（PDA）培养基，初始pH值6.0，接种量7%，装液量200 mL/500 mL，发酵温度32 ℃，130 r/min条件下振荡培养3 d。在此优化条件下，乙醇降解率为29.77%，表明罗汉果内生菌具有降解乙醇的潜力。

Screening of ethanol-degrading strains from Siraitia grosvenorii endophytes and optimization of fermentation conditions

Endophytes were isolated from Siraitia grosvenorii plants in Longsheng County, Guangxi by traditional culture and isolation method, and the strains with ethanol degradation activity were screened by determining ethanol tolerance and potassium dichromate-sulfuric acid method, and were identified by morphological observation and molecular biology techniques. Taking the ethanol degradation rate as the evaluating index, the fermentation conditions were optimized by single factor tests and orthogonal tests. The results showed that 68 endophytes were isolated from S. grosvenorii, from which a strain G-1 with high ethanol degradation activity was screened, and was identified as Fusarium oxysporum. The optimal fermentation conditions of the strain for ethanol degradation were potato dextrose agar (PDA) medium, initial pH value 6.0, inoculum 7%, loaded liquid 200 ml/500 ml, fermentation temperature 32 ℃, and 130 r/min shaking culture for 3 d. Under these optimized conditions, the ethanol degradation rate was 29.77%, indicating that S. grosvenorii endophytes had the potential to degrade ethanol.