Hub Metabolites Promote the Bioflocculant Production in a Biomass-Degrading Bacterium Pseudomonas boreopolis GO2

Introduction: The low yield of bioflocculants has been a bottleneck problem that limits their industrial applications. Understanding the metabolic mechanism of bacteria that produce bioflocculants could provide valuable insights and strategies to directly regulate their yield in future. Methods: To investigate the change of metabolites in the process of bioflocculant production by a biomass-degrading bacterium, Pseudomonas boreopolis GO2, an untargeted metabolome analysis was performed. Results: The results showed that metabolites significantly differed during the fermentation process when corn stover was used as the sole carbon source. The differential metabolites were divided into four co-expression modules based on the weighted gene co-expression network analysis. Among them, a module (yellow module) was closely related to the flocculating efficiency, and the metabolites in this module were mainly involved in carbohydrate, lipid, and amino acid metabolism. The top 30 metabolites with the highest degree in the yellow module were identified as hub metabolites for bioflocculant production. Finally, 10 hub metabolites were selected to perform the additional experiments, and the addition of L-rhamnose, tyramine, tryptophan, and glutaric acid alone all could significantly improve the flocculating efficiency of GO2 strain. Conclusion: These results indicated that the hub metabolites were key for bioflocculant production in GO2 strain, and could help guide the improvement of high-efficiency and low-cost bioflocculant production.