产叶酸菌株的筛选及其发酵条件的优化

从土壤样本中筛选分离得到的菌株R-1和S-1具有产叶酸的能力,进行单因素实验和正交分析,优化碳源、氮源、初始pH、发酵时间等条件,叶酸产量提高约为10%;加入前体物质对氨基苯甲酸(PABA),菌株R-1和S-1产叶酸的能力显著提高,分别提高了2倍和1.8倍;最后进行正交分析得出各菌种的最佳发酵产叶酸的因素选择。结果显示,菌株R-1的最佳产叶酸条件是葡萄糖25g/L,柠檬酸铵4g/L,PABA0.3g/L,接种量2%,培养时间24h,初始pH6.5,叶酸产量达到了1.92μg/mL;菌株S-1最佳产叶酸条件是蔗糖20g/L,柠檬酸铵2g/L,PABA0.3g/L,接种量3%,培养时间48h,初始pH5.5,叶酸产量为1.31μg/mL。

Screening of folic acid producing strains and optimization of fermentation conditions

Strain R-1 and S-1 which can synthesize folic acid were isolated from soil sample.Single factor experiments and orthogonal experiments were conducted,and the optimization of fermentation conditions(carbon and nitrogen source,initial pH,fermentation time) could increase folic acid levels by approximately 10%.The addition of PABA resulted in about two-fold increase in Strain R-1 of folic acid yields,while the Strain S-1 increased 1.8-fold.The optimal fermentation conditions for strain R-1 were as follows:glucose 25g/L,ammonium citrate 4g/L,PABA 0.3g/L,inoculation volume of 2%(v/v),initial pH 6.5,fermentation time 24h and the folic acid yield was up to 1.92μg/mL.Meanwhile,the folic acid yields by strain S-1 was 1.31μg/mL when fermentation was performed at sucrose 20g/L,ammonium citrate 2g/L,initial pH5.5 for 48h,with inoculation volume of 3%(v/v),PABA dosage of 0.3g/L.