Physiology of exopolysaccharide production by Azotobacter vinelandii from 4-hydroxybenzoic acid

The relationship between exopolysaccharide (EPS) production by Azotobacter vinelandii ATCC 12837 from 4-hydroxybenzoic acid as sole carbon source and other physiological parameters was investigated. In relation to growth, Azotobacter needed more time in 4-hydroxybenzoic acid to reach levels of biomass similar to those obtained when sugars were used, although the phenolic compound led to a more extensive exponential phase. The encystment process was initiated after cells had grown for 24 h, in which small amounts of EPS were synthesized and poly-beta-hydroxybutyrate (PHB) accumulation began. Both polymers, EPS and PHB, showed a similar evolution with time, as well as the formation of cysts, which points out the existence of a relation between these parameters. This was corroborated by a statistical study, in which significant correlations (P<0.05) were observed when each parameter was compared to the two others.