Exopolysaccharide production by Bacillus cereus GU812900, a fouling marine bacterium

Abstract

The aim of the study was to isolate the exopolysaccharides (EPS) from the active biofilm bacterium Bacillus cereus GU 812900 which was isolated from the stainless steel test panel and deployed in the Vellar estuary for a period of about four weeks. The deployed stainless steel test panels when analyzed revealed a direct relationship between the rate of corrosion and the concentration of EPS that is, the rate of corrosion increased with an increase in the concentration of EPS and the period of immersion. Growth and EPS production by B. cereus strain GU812900 was studied in a basalt salt solution (BSS) containing (g/1); NaCl, 30.0; KCl 0.75; MgSO4.7H2O, 7.0; NH4Cl, 1.0; K2HPO4, 0.7; KH2PO4. 0.3; glucose, 10.0 and 1 ml of trace metal solution. The rate of EPS production in batch cultures was highest during the late log phase of the growth then stationary phase. The EPS was recovered from the culture supernatant by using ethanol precipitation – dialysis procedure. Chemical composition of EPS revealed that it is primarily composed of natural sugars, proteins, phosphates and sulphates. The EPS production was influenced by carbon, nitrogen and phosphate concentrations in the growth medium. EPS produced by B. cereus GU812900 is a heteropolysaccharide which influence the corrosion. The FTIR analysis revealed the functional groups of the EPS. The results of the study was expressed the relationship between biocorrosion and biofilm formation of the stainless steel test panels. Key words: Biofilm, exopolysaccharides (EPS), sequencing, secondary metabolite, characterization, FTIR analysis.