Cellulases from the ruminal fungus Neocallimastix frontalis EB188

摘要

Cellulase enzymes from the ruminal fungus Neocallimastix frontalis EB188 were studied. Seven carboxylmethylcellulases (both endoglucanases and exoglucanases), six Avicelases and four $beta$-glucosidases (or cellobiases) were separated using hydroxylapatite column chromatography. One $beta$-glucosidase and one cellobiase were purified to homogeneity using hydroxylapatite, gel filtration and ion exchange chromatographies and polyacrylamide gel electrophoresis. The molecular weights, isoelectric points, pH and temperature activity optima, and metal ion inhibitions of these two enzymes were determined. Both enzymes hydrolyzed disaccharides or sugar derivatives, possessed different kinetic characteristics on a variety of substrates and were inhibited by various sugars or sugar derivatives. It was concluded that the cellulase enzymes of ruminal fungi are typical of fungal glycoside hydrolases and mediate the degradation of cellulose present in the rumen of cattle.