Evaluation effect of recombinant lytic polysaccharide monooxygenases added to Aspergillus fumigatus var. niveus cocktail in saccharification of sugarcane bagasse

Abstract

Background: Lignocellulosic biomass is an advantageous alternative to produce biofuels, despite its recalcitrant characteristic. There are microorganisms in nature capable of efficiently degrade biomass, such as the filamentous fungi. Among them, Aspergillus fumigatus var. niveus (AFUMN) has a wide variety of carbohydrate-active enzymes (CAZymes), especially hydrolases, but a low number of oxidative enzymes in its genome. To confirm the enzymatic profile of this fungus, this work analyzed the secretome of AFUMN cultured in sugarcane bagasse as sole carbon source. As expected, the secretome showed a predominance of hydrolytic enzymes compared to the oxidative activity. However, it is known that hydrolytic enzymes act in synergism with oxidative proteins to efficiently degrade cellulose polymer, such as the LPMOs (Lytic Polysaccharide Monooxygenases). Results: Thus, three LPMOs from the fungus Thermothelomyces thermophilus (TtLPMO9D, TtLPMO9H, and TtLPMO9O) were selected, heterologous expressed in Aspergillus nidulans, purified, and used to complement the AFUMN secretome aiming to evaluate the supplementation effect in the saccharification of sugarcane bagasse process. The saccharification assay was carried out using different concentrations of AFUMN secretome supplemented with recombinant T. thermophilus LPMOs, as well as ascorbic acid as reducing agent for oxidative enzymes. Conclusions: Through a statistic design created by Design-Expert software, we were capable to analyze a possible cooperative effect between these components. The results obtained indicated that, in general, the addition of TtLPMO9D and ascorbic acid did not favor the conversion process in this study, while TtLPMO9O had a highly significant cooperative effect in bagasse saccharification compared to the control using only AFUMN secretome.