Produção de glicosil hidrolases por Trichoderma harzianum para o processo de sacarificação da biomassa vegetal

Abstract

Currently the great challenge for the production of second generation ethanol is to reduce thecost of the enzymes. It is possible to reduce part of this cost by carrying out an optimization ofthe process fermentation using sources of cellulase-induction that allow further growth of fungalbiomass, and increased secretion of proteins. The use of a mutant strain with overexpression ofhemicelulolytics activators could increase expression of the enzymes of interest and therebycontribute to cost reduction. This work aimed to study the production of enzymes involved inthe degradation of biomass by the newly isolated strain of Trichoderma harzianum P49P11focusing on the improvement of the submerged fermentation processes and on the use molecularbiology tools to improve the fungal strain. Regarding the fermentation process, the effects ofdifferent inducing sources were evaluated in flasks and bioreactor using statistical experimentaldesign tools and strategies to enhance biomass in the pre-culture step. For fungal strainimprovement, it was used molecular biology tools for the overexpression of two activators ofcellulases (xyr1 and lae1). A proteomic analysis of the T. harzianum enzymatic extract obtainedusing sugarcane bagasse pretreated by steam explosion followed by delignification (BED) wasperformed. The results showed that the best source for inducing cellulase was BED + sucrose(3: 1), reaching values of 1.21 FPU/mL 80.0U/mL of xylanase and 17.30 U/mL of β-glucosidase. The proteomic analyis identificated 24 different glycoside hydrolases and fourCBM proteins, within 12 different CAZy families. From this study, the enzymatic cocktailproduced "on site" could be supplemented using two accessory enzymes, pectinase and α-Larabinofuranosidase,leading to an increase of 100% of the hydrolysis yield. Regarding thestudy of carbon sources in the pre-culture step, it was possible to increase cellulases productionin 2 times using glycerol as the initial carbon source, followed by inducing carbon source(BED). The xyr1 and lae1 overexpression influencied positively the FPase, CMCase, xylanaseand β-glucosidase production, representing a new approach to increase production of theseenzymes.