A novel acidic laminarinase derived from Jermuk hot spring metagenome.

Laminarinase, an enzyme with a specific affinity for laminarin-a complex polysaccharide found in the cell walls of brown algae and select marine organisms-was investigated in this study. We cloned and characterized a gene encoding a putative glycoside hydrolase family 16 (GH16) laminarinase derived from the Jermuk hot spring metagenome. The resulting product, named Jermuk-LamM, represents a novel 1,3-β-D-glucanase with 48.1% amino acid sequence similarity to previously characterized GH16 family members catalogued in the NCBI database. To date, this stands as the sole described endo-1,3-β-D-glucanase from the Fidelibacterota phylum, which was recently reclassified from Marinimicrobia. Jermuk-LamM, identified as an acidic laminarinase, exhibits optimal enzymatic activity at pH 5.0 and a temperature of 55 °C, maintaining its function for a duration of at least 7 h. Jermuk-LamM is an enzyme that efficiently hydrolyzes both soluble and insoluble (1,3)-β-D-glucans, as well as (1,3;1,4)-β-D-glucans, with a marked preference for laminarin. This enzymatic activity facilitates the valorization of macroalgal biomass by predominantly producing monosaccharides and disaccharides. These hydrolysis products can subsequently be converted into energy carriers such as alcohol, methane, and hydrogen. The enzyme's specific activities, coupled with its resistance to various additives, render Jermuk-LamM a promising candidate for various industrial applications, encompassing the realms of biofuel and pharmaceutical production. KEY POINTS: • Jermuk hot springs have significant potential as a source of novel enzymes. • Jermuk-LamM has less than 50% amino acid similarity to known enzymes. • It is the first enzyme characterized from the Fidelibacterota phylum.