Marine bacterium <i>Cobetia</i> sp. strain GM produces fucose-rich extracellular polymeric substance

Several extracellular polymeric substances (EPS) produced by bacteria have beneficial applications in the food, pharmaceutical, and cosmetic industries as gelling agents, stabilizers, thickeners, and bioactive ingredients. Most commercialized EPS are derived from soil bacteria, but studies on EPS produced by marine bacteria are scarce. We isolated a marine bacterium Cobetia sp. strain GM, which produces viscous EPS (glycoprotein). Viscosity measurement showed that the EPS of strain GM (GM-EPS) was comparable to commercialized bacterial EPS. Among the tested Cobetia strains, GM-EPS and Cobetia crustatorum EPS were significantly more viscous than other known Cobetia spp. The major constituents of GM-EPS polysaccharide were fucose, glucose, and galactose, which was distinct from exopolysaccharide of known Cobetia spp. This is the first report of a Cobetia sp. strain that produces fucose-rich EPS. GM-EPS protein was rich in hydrophobic and uncharged nonpolar amino acids. GM-EPS exhibited strong emulsion-stabilizing activity that was 1.5 times higher than xanthan.