The Online Morphology Control and Dynamic Studies on Improving Vitamin B₁₂ Production by Pseudomonas denitrificans with Online Capacitance and Specific Oxygen Consumption Rate

The relationship between the morphological character of Pseudomonas denitrificans and vitamin B₁₂ synthesis based on real-time capacitance measurement and online specific oxygen consumption rate (Q_O2) control was established for enhancing vitamin B₁₂ production. Results demonstrated that the threshold Q_O2 value lower than 2.0 mmol/gDCW/l would greatly stimulate the state transfer from the cell number growth phase to the cell elongation phase and promote rapid vitamin B₁₂ biosynthesis, while the vitamin B₁₂ biosynthesis rate could also be inhibited when the rate of cell’s length-to-width ratio (ratio-LW) was higher than 10:1. Furthermore, the optimal morphology controlling strategy was achieved based on online Q_O2 control, which increases the appropriate active cell numbers at the former phase, and then control the elongation of ratio-LW no more than 10:1 at the vitamin B₁₂ biosynthesis phase. The maximal vitamin B₁₂ production reached 239.7 mg/l at 168 h, which was improved by 14.7 % compared with the control (208 mg/l). This online controlling strategy would be effectively applied for improving industrial vitamin B₁₂ fermentation.