An in-depth characterization of the carbohydrate active enzymes from Bacillus altitudinis PS213

Abstract

BACKGROUND The need for clean energy, renewable resources, and circular economy has fostered the research in plant biomass degradation (PBD) catalyzed by microorganisms. The bovine rumen is among the best studied environments where PBD takes place. In this organ, the plant cell wall components (a combination of cellulose, hemicellulose and pectin) is enzymatically digested by carbohydrate-active enzymes (CAZymes) secreted by the microorganisms living in it. OBJECTIVES In this study, we report the complete circular genome sequence of a Bacillus altitudinis strain PS213, with annotation of the secreted CAZymes encoded in its genome and describe in depth their 3D structure. METHODS The genome was assembled using Unicycler from a combination of long and short reads (Illumina MiSeq and ONT). The predicted proteins were submitted to dbCAN to identify the putative CAZy. The 3D structure of secreted plant cell wall degrading enzymes was estimated using AlphaFold, and compared to experimentally determined structures to infer substrate binding specificity and catalytic mechanism. RESULTS The genome assembly resulted in a single contig of length 3.896.825 with GC%=41.2. It encoded 3955 proteins (avg protein length 287.6 aa), resulting in a coding ratio of 87.6%. We found 97 CAZy proteins, including 24 proteins presenting a secretory signal peptide and 21 proteins annotated as hypothetical proteins. The identification and in-depth description of known and novel CAZymes from B. altitudinis PS213 pave the way toward the improvement of plant biomass degradation processes with multiple possible biotechnological applications in the treatments of different wastes, feed stocks and composting materials