Genomic and functional characterisation of exopolysaccharide biosynthesis in marine bacterium Alteromonas sp. PRIM-28 with emulsifying and anti-inflammatory activities.

Bacterial exopolysaccharides (EPS) are structurally heterogeneous biopolymers governed by species- and strain-specific biosynthetic pathways and with diverse biotechnological applications. The study investigated EPS biosynthesis in a marine bacterium, Alteromonas sp. PRIM-28 through an integrated genomic and experimental approach. Whole-genome sequencing and functional annotation were performed to identify the gene clusters and regulatory elements associated with EPS biosynthesis. The salt tolerance of the bacterium was studied at salt concentrations of up to 25%. EPS production was assessed using the ethanol precipitation method and partial characterisation, including emulsification and anti-inflammatory assays. Draft genome contained 3444 coding sequences with 97.6% completeness. Phylogenetic and ANI analyses confirmed its close relation to Alteromonas fortis (96.2%). Genome mining identified wzy-dependent and generic-cellulose EPS biosynthesis clusters along with the presence of epsCDEFHLM genes. CAZyme and KEGG analysis revealed diverse carbohydrate-active enzymes and complete central carbohydrate metabolism pathways, supporting EPS biosynthesis in PRIM-28. Presence of saline and oxidative stress-tolerance genes (nqrABCDEF, opuED, sglTSBC and katABEG) suggest bacterium's environmental adaptability. Genes associated with virulence factors and antimicrobial resistance were not identified supporting the suitability of the strain for industrial use. The strain tolerated salinity up to 15%. The highest EPS production was seen at 96 h (2.40 ± 0.09 g L-1). The EPS contained ~ 60% total sugars, showed emulsification activity against different oils, and exhibited anti-inflammatory activity in the albumin denaturation assay (80.7 ± 0.9%) comparable to positive control (p > 0.05). The combined genomic and functional evidence establishes the EPS biosynthesis in PRIM-28 and highlight its potential as a sustainable biopolymer source.