Trichoderma reesei (Hypocrea jecorina) Bgl1 is a Novel, Exo-Acting Glucanase and Xylanase

Trichoderma reeseiβ-glucosidase (Bgl1) is one of four enzymes demonstrated to act synergistically to degrade cellulose both in vitro and in vivo. Our work attempted to better understand the substrate specificity and potential biotechnological applications of Bgl1. T. reesei Bgl1H cleaves over 80% of the β-(1-4) and β-(1-3) linkages in β-glucan and 14% of the β-(1-4) linkages in amorphous cellulose, significantly more than any tested bacterial β-glucosidase. Bgl1H cleaves 50% of the β-(1-4) linkages in xyloglucan when supplemented with cellulase and α-xyloside. Approximately 20% conversion to glucose was obtained from insoluble β-(1,3)-linked curdlan using only Bgl1H; addition of a curdlanase resulted in conversion of approximately 70% of the curdlan to glucose. Bgl1H also produces xylose from xylooligosaccharides and debranched xylans. For both glucans and xylans, the relative rates of hydrolysis increase with increasing polysaccharide chain lengths. Bgl1H is able to partially degrade β-glucan in a variety of grain components; addition of endo-acting enzymes improved the enzyme’s performance on these grain components. The ability of this enzyme to produce monosaccharides from undigestible polysaccharides suggest it may have potential in improving utilization of carbohydrates in animal feed, fermentations, and other biotechnological applications.

Structural and functional studies of the glycoside hydrolase family 3 β-glucosidase Cel3A from the moderately thermophilic fungusRasamsonia emersonii

The filamentous fungusHypocrea jecorinaproduces a number of cellulases and hemicellulases that act in a concerted fashion on biomass and degrade it into monomeric or oligomeric sugars. β-Glucosidases are involved in the last step of the degradation of cellulosic biomass and hydrolyse the β-glycosidic linkage between two adjacent molecules in dimers and oligomers of glucose. In this study, it is shown that substituting the β-glucosidase fromH. jecorina(HjCel3A) with the β-glucosidase Cel3A from the thermophilic fungusRasamsonia emersonii(ReCel3A) in enzyme mixtures results in increased efficiency in the saccharification of lignocellulosic materials. Biochemical characterization ofReCel3A, heterologously produced inH. jecorina, reveals a preference for disaccharide substrates over longer gluco-oligosaccharides. Crystallographic studies ofReCel3A revealed a highly N-glycosylated three-domain dimeric protein, as has been observed previously for glycoside hydrolase family 3 β-glucosidases. The increased thermal stability and saccharification yield and the superior biochemical characteristics ofReCel3A compared withHjCel3A and mixtures containingHjCel3A makeReCel3A an excellent candidate for addition to enzyme mixtures designed to operate at higher temperatures.