大肠杆菌CCTCC M208088发酵生产聚唾液酸的pH控制策略

研究了不同pH值控制策略对大肠杆菌CCTCC M208088发酵生产聚唾液酸的影响。采用高浓度磷酸盐培养基(20g/L磷酸氢二钾)缓冲pH值,聚唾液酸产量达到1.9g/L,但大量磷酸盐残留在发酵液中,影响聚唾液酸的后提取处理。把培养基中磷酸盐的质量浓度降至2.5g/L,同时流加2mol/L氢氧化钠溶液控制pH,聚唾液酸产量提升至2.3g/L,但是NH4+在发酵前期16h即消耗完毕。进一步采取氨水流加控制pH策略,聚唾液酸产量提升至3.2g/L,同时菌体浓度大幅增加至12.5g/L,导致40g/L初始山梨醇在20h耗尽。最后,在氨水控制pH的同时,向发酵体系中流加山梨醇,聚唾液酸产量和生产强度分别达到了4.8g/L和0.16g/(L.h),比优化前(高浓度磷酸盐发酵)分别提高了152%和188%。

pH Control Strategy in the Polysiaic Acid Fermentation Production by Escherichia coli CCTCC M208088

Effect of the different pH control strategies on the PSA production by Escherichia coli CCTCC M208088 was compared in this study.Those strategies including:(1)when 20 g/L K2HPO4 was presented in the medium,the titer of PSA achieved at 1.9 g/L PSA,however,the high-level residual K2HPO4 in broth bring difficult to the following PSA purification.(2)with 2.5 g/L K2HPO4 and feeding of 2 mol/L NaOH solution,the titer of PSA was 2.3 g/L;(3)the PSA titer was increased to 3.2 g/L by feeding of ammonia water as pH control agent.Furthermore,the feeding of ammonia could accelerated sorbitol consummation;(4) To further promote PSA production,a novel strategy using ammonia water for pH control coupling with sorbitol supplementation at a constant feeding speed was adopted.As a result,PSA production and productivity were increased separately to 4.8 g/L and 0.16 g/(L·h),which was 152% and 188% higher than that of the control(without pH control).