pH值对普鲁兰多糖发酵的影响及其机理分析

Mechanism Analysis and Influence of pH on Pullulan Fermentation

探究不同pH值条件对出芽短梗霉CGMCCNO.7055合成普鲁兰多糖的影响。同时通过测定合成普鲁兰多糖的前体尿苷二磷酸葡萄糖(uridine diphosphate glucose,UDPG)含量及其相关酶磷酸葡萄糖变位酶(phosphoglucomutase,PGM)和UDPG焦磷酸化酶(Uridine diphosphate glucose pyrophosphorylase,UGPase)活性来分析普鲁兰多糖合成机理。结果发现一种双阶段调控pH值的方法,即第一阶段,发酵开始后24 h(OD620<0.5)控制初始pH 6.0;第二阶段,发酵24 h后(OD620>0.5)调控pH值到5.0并维持恒定,此阶段磷酸葡萄糖变位酶(PGM)和UDPG焦磷酸化酶(UGPase)活性最高。采用该方法使普鲁兰多糖产量达到(92.5±2.41)g/L,生物量达到(13.87±0.89)g/L,经相关性检验发现该发酵条件下普鲁兰多糖产量与尿苷二磷酸葡萄糖含量呈显著负相关关系。

Influence of different pH was studied to influence on pullulan production by Aureobsidium pullulans CGMCCNO.7055. UDP-glucose level and its related enzymes that was phosphoglucomutase （PGM） and Uridine diphosphate glucose pyrophosphorylase（UGPase） were measured, which was used to analyze the fermentation mechanism. It was found a method that was two-phase controlling pH for fermentation. It showed that the first phase was controlled initial pH value to 6.0 in 24 h of the fermentation, then the second phase was controlled constant pH to 5 after fermenting 24 h（OD620〈0.5）. It expressed highest activity of PGM and UGPase under controlled constant pH to 5.0. The yield of pullulan reached to （92.5±2.41）g/L and the biomass obtained to （13.87±0.89）g/L under using this method. The correlation test found that there was a significant negative correlation between the yield of pullulan and content of UDPG.