大肠杆菌CCTCC M208088发酵生产聚唾液酸的pH控制策略

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

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%。

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).