控制pH环境对出芽短梗霉胞外多糖合成的影响

THE EFFECTS OF A CONTROLLED pH ENVIRONMENT ON POLYSACCHARIDE SYNTHESIS BY AUREOBASIDIUM PULLULANS

采用添加 Ca CO3 和 HCl的方法研究了 p H对出芽短梗霉多糖发酵的影响规律。在 P2培养基中发酵2 4 h,该菌有一个强烈的产酸期 ,导致 p H迅速下降到 3.6左右。在此 p H环境下继续发酵 12 0 h,多糖产量仅为 5.9g/ L。如果用 MP2培养基 (P2 + 0 .5% Ca CO3 )发酵 ,由于 Ca CO3 缓冲了发酵 p H的下降 ,在整个发酵过程中 p H值可以维持在 5.0以上 ,多糖产量达到 31g/ L。该菌的多糖合成不仅与发酵初始 p H有关 ,关键还在于整个发酵过程中发酵 p H值必须维持在 5.0以上。

The effect of pH on the extracellularpolysaccharide synthesis by Aureobasidium pullulans was studied by addding CaCO 3and HCl.Cultivated in P2 liquid medium for 24h,pH dropped to 3.6 because of strongly producing acid.Under this low pH environment,further fermentation for 120h,only 5.9g/L of polysacharide was obtained.When grown in MP2 medium contaning0.5% CaCO 3,the pH was kept above 5.0 during 144 hours,production of polysaccharide increased to 31g/L. The detailed information of effects of controlled pH on polysaccharide production showed an optimal pH value 5.0 must be maintained through the fermentative period.