Proteome analysis of the spontaneous oscillatory behavior in 1,3-propanediol production from glycerol by Clostridium butyricum

The oscillatory cultures in biological systems offer an opportunity for understanding the metabolic mechanism, regulation, and constraint. This study focuses on the particular spontaneous oscillation during continuous 1,3-propanediol (1,3-PDO) fermentation by Clostridium butyricum. A sustained oscillation occurred was triggered by 88 g/L glycerol at a dilution rate of 0.048 h⁻¹. The oscillatory behavior started at approximately 35 h and sustained for over 530 h with an average oscillation period of 35 h. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that a total of 46 proteins associated with glycerol metabolism were characterized. Aldehyde-alcohol dehydrogenase (AdhE), pyruvate:ferredoxin (lavodoxin) oxidoreductase (PFOR), and L-lactate dehydrogenase (LDH) with high centrality degree and compact coefficient were identified as the most crucial proteins in the protein-protein interaction network. Various proteins involved in Fe²⁺ regulation, such as AdhE, PFOR, glycerol dehydrogenase, 1,3-propanediol oxydoreductase, glycerol dehydratase activating protein, pyruvate formate lyase, nitrogenase, ferredoxin:NADP⁺ reductase, and hydrogenase were crucial for the spontaneous oscillation. These findings demonstrate that the level of Fe²⁺ influences the coordination of spontaneous oscillation in glycerol conversion to 1,3-PDO in C. butyricum. Finally, a sustained oscillatory behavior induced in response to a change in Fe²⁺ concentration further verifies Fe²⁺ limitation as a valve to generate oscillation.