Engineering <i>Trichoderma reesei</i> for the hyperproduction of cellulose induced protein 1 (Cip1) on a sophorose-containing inducer to efficiently saccharify alkali-pretreated corn stover

<i>Trichoderma reesei</i> was induced to produce cellulase by a combination of glucose and β-disaccharide; however, lower levels of auxiliary proteins for degrading lignocellulosic biomass were detected by iTRAQ analysis compared with cellulose as an inducer, especially cellulose induced protein 1 (CIP1). In this study, A <i>pdc1</i> promoter-driven overexpression of the endogenous <i>Trcip1</i> gene was observed in <i>T. reesei</i> Rut C30, and the <i>Trcip1</i> transcription levels of the two transformants, <i>T. reesei</i> OE-cip1-1 and OE-cip1-2, demonstrated 31.2- and 164.6-fold increases, respectively, but there was no significant change in cellobiohydrolase, endoglucanase and filter paper activity at 48 h. The crude enzyme was then used to hydrolyze corn stover. For <i>T. reesei</i> OE-cip1-1 and OE-cip1-2, the hydrolysis efficiency increased by 25.0 and 28.6% with a solid loading of 5% at 2 h, respectively. Simultaneously, 85.5 and 85.2 g/L glucose were released using a cellulase cocktail at high solid loading (20%), and these glucose release rates were significantly greater than that of <i>T. reesei</i> Rut C30 cellulase (77.4 g/L) at 120 h. Furthermore, scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that the enhanced hydrolysis efficiency was primarily triggered by the decrease in the crystallinity of lignocellulose, and the fiber structure had varying degrees of loosening and disintegration.