Deleção parcial do fator de transcrição ACE1 para otimização da produção de celulases por trichoderma reesei RUT-C30

Abstract

Second generation bioethanol employs lignocellulosic materials in its preparation. One of the steps for these materials degradation utilizes cellulases produced by microorganisms. Among these, Trichoderma reesei fungus is one of the main cellulases producers used in industry. This fungus genetic modification can lead to enzimes production optimization, reducing cost and improving biofuels manufacture. Thus, the present work objective was delete the sequence encoding zinc fingers motifs of cellulase ACE1repressor transcription factor from T. reesei RUT-C30 fungus, seeking enzymatic production optimization. In primers construction for amplification ACE1 regions 5’ and 3' and the hph selection marker, which confers hygromycin B resistance, Joint Genome Institute - JGI site and the BioEdit ® program were used. The deletion cassette with pRS426 vector construction was mediated by Saccharomyces cerevisiae SC9721 yeast. After the cassette construction, T. reesei RUT-C30 transformation was made by protoplast and this transformation confirmation was effected by part of the hph using hphNestF and hphNestR amplification primers. After transformation with mutants obtained, endoglucanase, exoglucanase and total cellulase activity was quantified with carboxymethylcellulose substrates (CMC), microcrystalline cellulose (Avicel®) and Whatman paper filter (PF), respectively. The enzymatic production and biomass hydrolysis efficiency were performed comparing RUT-C30 strain for mutants. After deletion cassette construction, a 3501 bp fragment amplification confirmed the cassette formation. Posteriorly, RUT-C30 strain transformation, a 989 bp amplification was observed, confirming the 3 mutants target sequence deletion. With cellulase activity assay, 3 transformed strain showed higher enzymatic production when compared to RUT-C30 strain. In this comparison, a significant statistical difference was observed of RUT-C30Δace1-1 strain with Avicel® and PF (p <0.001) CMC (p <0.01), RUT-C30Δace1-2 strain with CMC (p<0,01) e PF (p<0,05), and RUT-C30Δace1-3 strain with Avicel (p<0,001), CMC and PF (p<0,01). The mutants also showed greater efficiency in biomass hydrolysis, with release sugar increase between 21 and 42%. Based on this study, mutants are promising for most efficient and viable ethanol production. Nevertheless, additional tests must be carried out to better understand these fungi applicability in the industrial level.