State Key Laboratory of Materials-Oriented Chemical Engineering, College of Food Science and Light Industry, Nanjing University of Technology, No. 5 New Model Road, Gulou District, Nanjing 210009, China.
Bioprocess Biosyst Eng. 2013 Sep;36(9):1165-76. doi: 10.1007/s00449-012-0843-9. Epub 2012 Oct 30.
The effects of oxidoreduction potential (ORP) regulation on the process of propionic acid production by Propionibacterium freudenreichii CCTCC M207015 have been investigated. Potassium ferricyanide and sodium borohydride were determined as ORP control agents through serum bottle experiment. In batch fermentation, cell growth, propionic acid and by-products distribution were changed with ORP levels in the range of 0-160 mV. Based on these analysis results, an ORP-shift control strategy was proposed: at first 156 h, ORP was controlled at 120 mV to obtain higher cell growth rate and propionic acid formation rate, and then it was shifted to 80 mV after 156 h to maintain the higher propionic acid formation rate. By applying this strategy, the optimal parameters were obtained as follows: the propionic acid concentration 45.99 g L(-1), productivity 0.192 g L(-1) h(-1), the proportion of propionic acid to total organic acids 92.26 % (w/w) and glycerol conversion efficiency 76.65 %. The mechanism of ORP regulation was discussed by the ratio of NADH/NAD(+), ATP levels, and metabolic flux analysis. The results suggest that it is possible to redistribute energy and metabolic fluxes by the ORP-shift control strategy, and the strategy could provide a simple and efficient tool to realize high purity propionic acid production with glycerol as carbon source.
氧化还原电位（ORP）调控对丙酸产生菌发酵生产丙酸的影响。通过摇瓶实验，确定了铁氰化钾和硼氢化钠为 ORP 调控剂。在分批发酵中，细胞生长、丙酸和副产物的分布随 ORP 值在 0-160 mV 范围内的变化而变化。基于这些分析结果，提出了一种 ORP 转换控制策略：首先在 156 h 内将 ORP 控制在 120 mV 以获得更高的细胞生长速率和丙酸生成速率，然后在 156 h 后将其转换为 80 mV 以维持更高的丙酸生成速率。应用该策略，得到了最佳的参数：丙酸浓度 45.99 g/L，产率 0.192 g/L·h，丙酸与总有机酸的比例为 92.26%（w/w），甘油转化率为 76.65%。通过 NADH/NAD(+)的比例、ATP 水平和代谢通量分析探讨了 ORP 调控的机制。结果表明，通过 ORP 转换控制策略可以重新分配能量和代谢通量，该策略为以甘油为碳源生产高纯度丙酸提供了一种简单有效的方法。
