Exopolysaccharide and poly-beta-hydroxybutyrate coproduction in two Rhizobium meliloti strains

The nature of carbon and nitrogen sources effects the coproduction of exopolysaccharide (EPS) and poly-beta-hydroxybutyrate (PHB) by the M5N1 and Su47 strains of Rhizobium melilot. Bacterial growth in nitrogen-deprived medium is limited, and facilitates EPS production rather than PHB production. Cells grown in glucose show a lag phase in EPS production, which is absent in EPS production from fructose and in PHB synthesis. The lag phase is related to the extracellular conversion of glucose to gluconic or 2-ketogluconic acids.