Cellulases and xylanases production by Humicola grisea var. thermoidea on different lignocellulosic substrates and their application in hemicelullase hydrolysis of sugar cane bagasse

Humicola grisea var. thermoidea is a deuteromycete which secretes a large spectrum of hydrolytic enzymes, when grown on lignocellulosic residues. The main cellulolytic enzyme secreted by H. grisea correspond to the 47 kDa celobiohydrolase (cbh1.2), while the 23 kDa endoxylanase (HXYN2) presented the main xylanase activity band on zymogram analysis. This study is focused on sugarcane bagasse hydrolysis through the cellobiohydrolase and xylanase. The fungus was grown on sugarcane bagasse (SCB), wheat bran (WB), rice straw (RS) and corn cob (CC) the carbon source. The major xylanase and avicelase activities were observed when the fungus grown on WB, while the major CMCase and FPase activities on SCB. Proteins secreted by H. grisea upon growth on WB (HgWB) and SCB (HgSCB) by 144 h were analyzed by SDS/PAGE and zymogram. The results suggested que HgWB and HgSCB presented a different pool of cellulases and xylanases and que the protein band with molecular mass corresponding to HXYN2 is visible only in HgWB while the protein band with molecular mass corresponding to cbh1.2 is visible in both culture supernatants, however is more intense in HgSCB. Pre-treated SCB hydrolysis was performed using an enzymatic mix containing different concentrations of HgWB, HgSCB, recombinant cbh1.2, recombinant HXYN2 and recombinant β-xylosidase Caudocelus crescentus (XYNB2). The best hydrolysis results were obtained using HgWB and HgSCB (0.75: 0:25) supplemented with HXYN2 (950 U), cbh1.2 (1.85 U) and XYNB2 (0.75 U).