Abstract
Coenzyme Q(10) (CoQ(10)) is crucial for human beings, especially in the fields of biology and medicine. The aim of this experiment was to investigate the conditions for increasing CoQ(10) production. At present, microbial fermentation is the main production method of CoQ(10), and the production process of microbial CoQ(10) metabolism control fermentation is very critical. Metabolic flux is one of the most important determinants of cell physiology in metabolic engineering. Metabolic flux analysis (MFA) is used to estimate the intracellular flux in metabolic networks. In this experiment, Rhodobacter sphaeroides was used as the research object to analyze the effects of aqueous ammonia (NH(3)·H(2)O) and calcium carbonate (CaCO(3)) on the metabolic flux of CoQ(10). When CaCO(3) was used to adjust the pH, the yield of CoQ(10) was 274.43 mg·L(-1) (8.71 mg·g(-1) DCW), which was higher than that of NH(3)·H(2)O adjustment. The results indicated that when CaCO(3) was used to adjust pH, more glucose-6-phosphate (G6P) entered the pentose phosphate (HMP) pathway and produced more NADPH, which enhanced the synthesis of CoQ(10). At the chorismic acid node, more metabolic fluxes were involved in the synthesis of p-hydroxybenzoic acid (pHBA; the synthetic precursor of CoQ(10)), enhancing the anabolic flow of CoQ(10). In addition, Ca(2+) produced by the reaction of CaCO(3) with organic acids promotes the synthesis of CoQ(10). In summary, the use of CaCO(3) adjustment is more favorable for the synthesis of CoQ(10) by R. sphaeroides than NH(3)·H(2)O adjustment. The migration of metabolic flux caused by the perturbation of culture conditions was analyzed to compare the changes in the distribution of intracellular metabolic fluxes for the synthesis of CoQ(10). Thus, the main nodes of the metabolic network were identified as G6P and chorismic acid. This provides a theoretical basis for the modification of genes related to the CoQ(10) synthesis pathway.