Untargeted Metabolomics Analysis on the Effect of Ventilation on the Production of 1,3-Propanediol by Klebsiella pneumoniae

Klebsiella pneumoniae is recognized as an efficient producer of 1,3-propanediol. The increase in ventilation rate promoted bacterial growth but inhibited the production of 1,3-propanediol. Bacterial cells were harvested after aeration fermentation at rates of 0 L/min (control group) and 6 L/min (experimental group) for durations of 12, 24, and 48 h. Intracellular metabolites underwent untargeted metabolomics analysis. The results indicate that the down-regulation of 2-oxocarboxylic acid metabolism during the initial phases of fermentation suggests enhanced energy production under high-ventilation fermentation conditions. In contrast, nicotinate and nicotinamide metabolism suggests low oxygen concentration hampers the conversion between NAD+ and NADH. The up-regulation of purine metabolism pathways during the mid-term of fermentation suggests that a consistently high-oxygen environment is not conducive to purine metabolism. During the late stage of fermentation, the up-regulation of 3,4-dihydroxyphenylalanine and 5,6-dihydroxyindole-2-carboxylate in the high-ventilation group of Tyr metabolism indicates an enhanced antioxidant capacity of the cell. This study presents metabonomic analysis elucidating the potential mechanism of glycerol fermentation by K. pneumoniae under varied aeration conditions.