pH值对聚谷氨酸发酵液粘度及聚合物结构的影响

生产中聚谷氨酸的发酵液非常黏稠(粘度达1.71Pa.s),这使除菌体提取聚谷氨酸非常困难。通过加酸或碱调节发酵液pH<5或pH>8可明显降低发酵液的粘度(其中pH3.5时粘度仅为pH6.5时的1/50左右)。将pH3.5的发酵液离心除菌(10 000×g,10 min)后超滤浓缩(滤膜孔径0.45μm,平均压力0.08 Mpa)1倍,再加入95%乙醇提取-γPGA,与pH中性时相比,可减少50%以上的能量消耗及40%的溶剂,但聚谷氨酸损失约10%。加酸或加碱处理可使发酵液中-γPGA的分子结构发生改变,分子质量降低,这对生产高分子质量的聚谷氨酸不利,但对生产低分子质量产物是适宜的。

Effects of pH Value on Poly(γ-Glutalmic acid) Culture Broth Viscosity and Polymer Structure

The culture broth of poly(γ-glutamic acid) was very viscous and its viscosity could reached 1.71(Pa·s.) Adjusting the solution pH<5 or pH>8 could clearly reduce viscosity.By concentrating the broth volume to 1/2 of the beginning with ultra-filtration(nominal pore diameter 0.45μm,0.08MPa) after centrifugation(10 000×g,10 min),the energy consumption would be reduced about 50% and the amount of 95% ethanol required for precipitation could be reduced 40% of that without the treatment,the loss of γ-PGA reached about 10% during the process.However,adding acid or alkali could change the polymer structure and make it breakdown.This treatment was disadvantageous to high molecular weight polymer production,but it was a feasible method to produce low molecular weight polymer.