Elucidating the exopolysaccharide biosynthesis in Pediococcus acidilactici BCB1H regulated by iron (Fe²⁺) using a multi-omics approach

One of the vital functional biopolymers produced by lactic acid bacteria (LAB) is exopolysaccharide (EPS) that has been extensively studied, but less research has been done on the EPS production by pediococci. In this study, the EPS synthesis in Pediococcus acidilactici BCB1H regulated by Fe²⁺ was investigated by a multi-omics method. Adding Fe²⁺ (0.6 g/L) in a semi-defined medium was shown to significantly increase the EPS production from 225.5 to 271.5 mg/L by BCB1H. Joint transcriptomics and proteomics analyses on BCB1H under Fe²⁺ interference revealed upregulation of phosphotransferase systems (PTS), the key pathway to synthesizing EPSs. Further joint transcriptomics and metabolomics analyses showed a total of 22 differential metabolic pathways, including overall metabolic pathways, biosynthesis of secondary metabolites, metabolism of microorganisms in different environments. Integrated multi-omics analysis for the key differentially expressed genes, proteins and metabolites with synergistic effects revealed decarboxylating 6-phosphogluconate dehydrogenase (Gnd), acetyl-CoA carboxylase biotin carboxylase subunit (AccD) and EII sugar-specific permease (EIIs) genes that were upregulated, while glycerol kinase (GlpK) and alcohol dehydrogenase (AdhP) downregulated. Therefore, Fe²⁺ enhanced the EPS synthesis in BCB1H by promoting accumulation of fructose-6-phosphate, glycerate and malate, and reducing production of D-fructose-1,6-diphosphate and glycerone-phosphate, mainly by regulation of the pentose phosphate pathway, tricarboxylic acid cycle, glycolysis and gluconeogenesis pathways, and glycerolipid metabolism pathways. The present study was significant for further understanding the regulatory mechanism of EPS biosynthesis in LAB.