增大罐压提高脱氮假单胞菌发酵生产维生素B12的产量

摘要

[Objective] The pressure of fermenter was enhanced in order to increase the concentration of vitamin B12. [Methods] Metabolic flux analysis (MFA) was used to analyse the fermentation process of vitamin B12 production by Pseudomonas denitrifwan. [Results] The results indicated that the metabolic flux of oxaloacetic acid from phosphoenolpyruvate car-boxylation was increased when the synthesis rate of vitamin B12 increased, in order to meet the demand for precursor supply to vitamin B12 production. A novel control strategy was designedas following. The pressure of fermenter was enhanced in order to increase the solubility of carbon dioxide in aqueous solution at steady phase of fermentation, so more carbon dioxide was carboxylated to oxaloacetic acid. The result showed that the concentration of vitamin B12 was 176 mg/L, 19.7% higher than the control batch (147 mg/L) at 160 hours. [Conclusion] the production of vitamin B12 by Pseudomonas denitrifican was improved by increasing the fermenter pressure.%[目的]提高发酵罐的罐压,增加维生素B12的产率.[方法]利用常规代谢通量分析(MFA)方法,对脱氮假单胞菌生产维生素B12的发酵过程进行研究.[结果]发现随着VB12合成速率的加快,磷酸烯醇式丙酮酸(PEP)羧化生成草酰乙酸(OAA)的通量明显加大,以满足维生素B12合成对前体的需求.根据该分析结果,对发酵工艺进行了改进,即在脱氮假单胞菌进入合成维生素B12阶段时,提高发酵罐的罐压,增加发酵液中二氧化碳的溶解度,从而强化了羧化回补途径.维生素B12的产率明显增加,发酵160 h的产物浓度为176 mg/L,比对照批次终浓度147 mg/L高出了19.7％.[结论]通过增大罐压提高了脱氮假单胞菌进入合成维生素B12的产量.