Production, characterization, and genomic insights of a human lectin-binding exopolysaccharide from Haloarcula japonica strain SST1

Hypersaline environments harbor halophiles capable of producing extracellular polysaccharides (EPSs). This study reports EPS production, chemical composition and genomic insights by the halophilic archaeon Haloarcula japonica strain SST1, isolated from a subterranean salt deposit in Avan, Armenia. The highest extracellular product (EP) yield (628.4 mg L−1) was achieved at 120 h cultivation in sucrose-supplemented medium. Sucrose-derived EP had high carbohydrate content (48.5%), while molasses yielded 275.2 mg L−1 with 20.8% carbohydrate. Gel filtration revealed a heterogeneous molecular mass (10–100 kDa). GC–MS, HPAE-PAD, and NMR identified a heteropolymer of mannose, galactose, and glucose. Genome sequence data confirmed genes for monosaccharide activation, polymerization, and secretion. Use of molasses as substrate highlights SST1’s potential as a cost-effective EPS producer for circular bioeconomy. Binding of raw EPS to human C-type lectins suggests possible biomedical applications in innate immunity modulation.