The lytic polysaccharide monooxigenases secreted by the fungus Chrysoporthe cubensis: Genomic analysis and impact on sugarcane bagasse saccharification

Abstract

This work aimed to identify and evaluate the impact of oxidoreductases secreted by Chrysoporthe cubensis COAD 3356 on the saccharification of sugarcane bagasse. Genomic analyses focusing on lytic polysaccharide monooxygenases from Auxiliary Activity family 9 (LPMO9s) indicated fourteen putative LPMO9-coding genes in the C. cubensis genome. The predicted proteins were clustered with other LPMO9s based on sequence similarity. We evaluated if the clusters correlate with LPMO9 function, such as substrate specificity and oxygenation regioselectivity, and with evolutionary features (phylo-specific proteins and the presence of genes coding for LPMO9 redox partners in fungal genomes). There was no apparent connection between the LPMO9 sequences and the evaluated functional properties. On the other hand, we detected clusters containing phylo-specific LPMO9, and a cluster enriched in LPMO9s from fungi with no genes coding for cellobiose dehydrogenase (CDH). Proteomic analysis using LC-MS/MS revealed the presence of seven LPMO9s in C. cubensis exoproteome, in addition to flavin-containing oxidoreductases. Saccharification of alkaline pretreated sugarcane bagasse in aerobic and anaerobic conditions using C. cubensis exoproteome fractions, which contained different LPMO9s, indicated that the CcLPMO9C and CcLPMO9D are better fitted than other LPMO9s secreted by C. cubensis for sugarcane bagasse saccharification.