Comparative metabolomics analysis of the key metabolic nodes in propionic acid synthesis in Propionibacterium acidipropionici

Propionic acid (PA) is an important platform chemical used in the agriculture, food, and pharmaceutical industries. The biosynthesis of PA by propionibacteria has become an attractive alternative to traditional petrochemical processes owing to the environmentally friendly features of biorefinery. In a previous study, we significantly increased PA production in Propionibacterium acidipropionici by improving acid tolerance via genome shuffling. In this study, we undertook metabolomics analysis of parental P. acidipropionici and its genome-shuffled mutant to find the key metabolic nodes influencing PA production. In total, 142 intracellular metabolites were identified, of which those produced in amounts of greater than twofold difference between the two strains were further investigated with principal components analysis. The regulatory functions of key metabolites involved in the PA biosynthetic pathway were also forecast and analyzed according to their potential impact on metabolism. The results indicated that the amounts of metabolic intermediates of glycolysis, the Wood–Werkman cycle, and amino acid metabolism differed markedly between parental P. acidipropionici and its mutants. Based on the results of comparative metabolomics analysis, exogenous addition of key metabolites (precursors and amino acids) was performed to improve PA production. Under optimized conditions, 105 mM lactate, 20 mM fumarate, and 30 mM succinate were added to the culture of P. acidipropionici CGMCC 1.2230 in a 3-L anaerobic fermenter, and the PA titer increased from 23.1 ± 12 to 35.8 ± 1.0 g/L. This study revealed the key metabolic nodes of PA synthesis in P. acidipropionici through comparative metabolomics analysis, which may be helpful for the metabolic engineering of P. acidipropionici for improved PA production.