高黏发酵液中γ-聚谷氨酸的分离纯化工艺生物化工

Separation and purification process of poly-γ-glutamtic acid from high-viscous broth

γ-聚谷氨酸(γ-PGA)是由多种杆菌产生的一种胞外多肽,发酵生产时由于黏度高导致菌液分离困难。文中优化了发酵液微滤除菌、超滤浓缩和醇析干燥的工艺参数。综合考虑渗透通量、压差和除菌率等参数,确定微滤最佳操作温度为40℃,最佳操作压差0.3-0.4 MPa,最佳稀释度为V(发酵液)∶V(水)=1∶2,除菌率最高可达92.47%,在此条件下可以保持较高的渗透通量和较快的浓缩液循环流速,使微滤过程更为高效,同时不会因压力过高而造成微滤膜过早堵塞。通过优化,选择超滤最佳的浓缩比为5,此时渗透通量为31.8 L/(m2·h),产物回收率为81.6%。对pH=3—10共9个梯度进行了考察,比较在不同pH值条件下醇析操作纯化γ-PGA的粗产量,最优pH=7可达到最好的沉淀效果。这一优化分离工艺具有应用于γ-聚谷氨酸生产的潜力。

The separation and purification of poly-γ--glutamtic acid （γ-PGA） from broth is very difficult due to high viscosity. The operating parameters were optimized to improve the performance of PGA isolation process containing micro-filtration, uhrafiltration and ethanol precipitation. With regards to the three parameters （permeation flux, pressure and cell removal ratio） , the micro-filtration operating conditions were optimized as follows ： temperature 40 ℃, pressure differential 0.3-0.4 MPa, the volume ratio of dilution between broth and water 1 ： 2. Under the above optimal conditions, 92. 47% of cells were removed from T-PGA broth. The optimal concentration rate of uhrafiltration was 5 ： 1, while the permeation flux was 31.8 L/（m2 · h） and 81.6% of T-PGA was retained. The effects of different pH were examined and the optimal pH was determined to be 7 for efficient PGA precipitate. The present work promised the potential large-scale production of PGA in the future