Identification of exopolysaccharide synthesizing genes in bacteria isolated from Bonny River in Rivers State, Nigeria

Microbial polysaccharide is the most important biopolymer secreted either by bacteria, fungi, or yeast as natural non-toxic, biodegradable and renewable sugar monomers. Microbial EPS owing to their interesting physicochemical and rheological properties has a wide range of industrial application such as in pharmaceuticals, cosmetics, food and Microbial enhanced oil recovery. This study was aimed to identify exopolysaccharide synthesizing genes in three bacterial isolates from Bonny River in Rivers State, Nigeria. The bacterial isolates were identified using the 16S rRNA gene sequence of the strains which carefully studied by making reference to the GenBank database using a BLAST search as Bacillus xiamensis, Bacillus safensis and Exiguobacterium aurantiacum using 16S rRNA PCR technique. Two priming Gylcosyltranferase genes (pGT) rfbp and cpsD were probed in the genome of the isolates after identification of the isolates. Two isolates Bacillus safensis and Exiguobacterium aurantiacum had both rfbp and cpsD genes while Bacillus xiamensis had only rfbp gene but no cpsD gene. The three isolates were examined for the Exopolysaccharide production on a minimal medium that contained g/l: KH2PO4 0.2, K2HPO4 1.5, MgSO4.7H2O 0.2, CaSO4.2H2O 0.1, FeCl3 0.002, yeast extract 0.5 and sucrose 20 and all three isolates produced EPS. At Optimum biomass of 0.15g/10 ml, the highest EPS yield of 10.20 g/l was obtained from Bacillus safenis. Exiguobacterium aurantiacum had optimum biomass of 0.11g/10ml with an EPS yield of 6.15g/l. The least biomass of 0.08g/10ml and EPS yield of 3.62 g/10ml was observed in Bacillus xiamensis. The biomass production was determined at Optical Density (OD) of 600nm while the EPS production was quantified by the Phenol Sulphuric acid method using glucose as a standard.