Secretome characterization of the lignocellulose-degrading fungi Pycnoporus sanguineus and Ganoderma applanatum

Abstract

C4 grasses are common species in rangelands around the world and represent an attractive option for second-generation biofuels production. Although they display a high polysaccharide content and reach great levels of biomass accumulation, there is a major technical issue to be solved before they can be considered as biofuels feedstock: lignin removal. Concerning this, Pycnoporus and Ganoderma fungal genera have been highlighted due to their ability to hydrolyze lignocellulose. The goals here were to evaluate the pretreatment efficiency using P. sanguineus and G. applanatum secretomes harvested from a glucose-free inductive medium and to identify the fungal enzymatic activities responsible for the lignin degradation and glucose release. The findings show that P. sanguineus secretome exhibits a higher activity of lignocellulolytic enzymes compared to the one from G. applanatum. Interestingly, zymograms in presence of glucose suggest that a {beta}-glucosidase isoform from P. sanguineus could be glucose-tolerant. The proteomic approach carried out allowed to identify 73 and 180 different proteins for G. applanatum and P. sanguineus secretomes, respectively, which were functionally classified in five main categories, and a miscellaneous group. Many uncharacterized proteins were found in both secretomes, reflecting that greater research is still needed for a better comprehension of lignocellulose degradation.