Prospecting exopolysaccharides produced by selected bacteria associated with marine organisms for biotechnological applications

In this study, bacteria associated with marine organisms were screened for the production of exopolysaccharides (EPSs) on MY media containing sea salts (2.5%–10%). Three selected isolates were identified as Alteromonas sp. PRIM-21, Nitratireductor sp. PRIM-24 and Enterobacter sp. PRIM-26 using 16S rRNA gene sequencing. Optimization of the growth and EPS production kinetics in relation to incubation time were assessed. The purified EPS yield was 590, 650 and 540 mg·L−1 culture media respectively in Alteromonas sp. PRIM-21, Nitratireductor sp. PRIM-24 and Enterobacter sp. PRIM-26. Biochemical and FTIR analyses revealed the presence of biologically important functional groups in the EPS produced by all the three isolates. The EPS produced by Nitratireductor sp. PRIM-24 and Alteromonas sp. PRIM-21 showed 2.0% sulfate content. These bacterial EPS also showed antioxidant and emulsifying activities and the EPS produced by Enterobacter sp.PRIM-26 showed significantly higher antioxidant activities in terms of superoxide (IC50 0.33 mg·mL−1) and DPPH (IC50 0.44 mg·mL−1) radical scavenging. It also showed higher emulsifying activities against selected hydrophobic substrates with EI24 values above 60%. From the results of the study, it can be concluded that the isolated bacteria produce EPS that can be investigated in detail for biotechnological applications.