Adsorption of Trichoderma reesei cellulases on protein-extracted lucerne fibers

Abstract

Protein-extracted lucerne fibers (PELF) had a higher adsorptive capacity for Trichoderma reesei cellulases than a variety of other cellulosic substrates compared on an equal carbohydrate basis. Adsorption at room temperature reached a maximum at about 5 min; desorption was directly proportional to the extent of carbohydrate solubilization. Cellulase binding conformed to a Langmuir isotherm; the maximum cellulasebinding capacity of PELF was 111 filter paper units per g dry weight. About 85% of the cellulase was recovered in the soluble fraction after PELF hydrolysis. Soluble carbohydrates in the hydrolysate inhibited cellulase adsorption to fresh substrate (50% inhibition at a hydrolysate concentration of 7% glucose equivalents). The effect of these carbohydrates on cellulase adsorption was a complex one composed of both enhancing and inhibitory influences. Artificial hydrolysates (known sugars in proportions identical to actual hydrolysates) inhibited adsorption, but glucose, cellobiose and xylose resulted in adsorption enhancement. Acid treatment of the hydrolysate to convert oligosaccharides to monomers increased reducing sugar concentrations and eliminated its capacity for adsorption inhibition. © 1988 Society for Industrial Microbiology.