Sulfated exopolysaccharide produced by Labrenzia sp. PRIM-30, characterization and prospective applications

Exopolysaccharides (EPS) are biopolymers produced by bacteria, having potential industrial applications. An EPS produced by a bacterium designated as PRIM-30 isolated from the deep seawater collected from offshore region of Cochin, India was studied. The isolate was identified as Labrenzia sp. based on 16S rRNA gene sequencing. Under optimum conditions for EPS production, the EPS yield was 840 mg L−1 culture medium. The average molecular weight of the EPS was 269 kDa and composed of glucose, arabinose, galacturonic acid and mannose in the ratio 14.4:1.2:1:0.6. Importantly, the purified EPS contained 4.76% (w/w) sulfate groups. Viscosity of the (1% w/v) EPS was 3.92 cP (shear rate 300 s−1, 25 °C). Anodic peak potential (Epa) of the EPS by cyclic voltametric measurement was −0.7 V. The EPS showed antioxidant activities with IC50 values of 640 and 190 μg mL−1, respectively, for the inhibition of DPPH and superoxide radicals. The EPS displayed a linear dose dependent increase in total antioxidant capacity and ferric reducing power activities. To date, only a very few marine alphaproteobacterial representatives have been reported for EPS production and this study for the first time, shows the production of a sulfated EPS by a member of the genus Labrenzia.