Supplementary Material for: Hub metabolites promote the bioflocculants’ 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 bioflocculants’ 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.

引言：生物絮凝剂产率低下一直是限制其工业应用的关键瓶颈问题。深入探究产生生物絮凝剂的细菌的代谢机制，可能为未来直接调控其产率提供宝贵的见解和策略。方法：为研究一种生物质降解菌Pseudomonas boreopolis GO2在生物絮凝剂生产过程中的代谢物变化，进行了非靶向代谢组学分析。结果：结果显示，当以玉米秸秆作为唯一的碳源时，在发酵过程中代谢物存在显著差异。根据加权基因共表达网络分析，差异代谢物被划分为四个共表达模块。其中，一个模块（黄色模块）与絮凝效率密切相关，该模块中的代谢物主要参与碳水化合物、脂质和氨基酸代谢。根据黄色模块中程度最高的前30个代谢物被识别为生物絮凝剂生产的枢纽代谢物。最终，选取了10个枢纽代谢物进行额外实验，单独添加L-阿拉伯糖、酪胺、色氨酸和戊二酸均能显著提高GO2菌株的絮凝效率。结论：这些结果表明，枢纽代谢物对于GO2菌株的生物絮凝剂生产至关重要，并有助于指导高效、低成本生物絮凝剂生产的提升。