Unveiling the CAZyme repertoire of a sponge-derived Pseudoalteromonas sp. strain for the degradation of marine polysaccharides

Abstract

Despite their well‐known importance to the holobiont homeostasis, carbohydrate‐active enzymes (CAZymes) from the sponge microbiome have to date been largely understudied from an industrial perspective. Enzymes that degrade marine polysaccharides (MPs) are receiving increasing attention as alternatives in the biorefinery sector and for use in the generation of high‐value‐added hydrolysis products. Screening of the agarolytic Pseudoalteromonas sp. strain PA2MD11, isolated from the Brazilian sponge Plakina cyanorosea, on selective media indicated that the strain degrades agarose, κ‐carrageenan and sodium alginate. Subsequently in silico analysis of the strain's genome indicated that around 3 % of the total genome encoded for CAZymes. These consisted mostly of glycoside hydrolases (GH) and glycosyltransferases (GT). Four agarase genes were also present, three from the family GH50 and one from the family GH16, with sequences from other free‐living and psychrophile Pseudoalteromonas genomes as its closest relatives. These agarases are structurally related to exo‐(GH50) and endo‐β‐agarases (GH16), and appear to encode for a complete agarolytic pathway. The two alginate lyases were classified as polysaccharide lyases (PL) from the families 6 and 17, with chondroitin‐ and heparin‐like domains, respectively, and shared common homologues sequences with an estuarine Pseudoalteromonas lipolytica strain. Data on the cloning and heterologous expression of these genes will be presented. To our knowledge, this is the first time that a “genome mining” based approach has been undertaken to identify these groups of MPs‐degrading CAZymes from cultivable members of the sponge microbiome.