Wednesday, November 7, 2007
293-11

Biochemical Characterization and Kinetic Properties of White Rot Fungal Beta-Glucosidase.

Priscilla M. Mfombep1, Zachary N. Senwo1, Omon S. Isikhuemhen2, and Robert W. Taylor1. (1) Natural Resources & Environmental Sciences, Alabama A&M University, 4900 Meridian St, Normal, AL 35762, (2) North Carolina A& T State University, Natural Resources and Environmental Desig, 1601 East Market Street, Greensboro, NC 27411

White rot fungi (WRF) are mushrooms that secrete enzymes to externally digest food for their growth and proliferation. Among the enzymes secreted by WRF for substrate degradation, β-glucosidase which is versatile relative to substrate specificity and important in many environment-friendly biotechnological processes for biomass conversion has not been evaluated in WRF. Therefore, the objective of this study was to quantify and characterize β-glucosidase activity in secretions of various WRF.

Residual liquid media after cultivation of seventeen selected WRF from six genera (Pleurotus, Grifola, Auricularia, Polyporus, Trametes, and Lentinula) were evaluated for β-glucosidase activity. β-Glucosidase activity in the extracts was assayed at 37oC for 30 minutes, using p-nitrophenyl β-D-glucopyranoside as substrate (prepared in 50 mM sodium acetate buffer, pH 5.0). The extracts showed significant difference at p < 0.5 in their total protein and carbohydrate contents. Most of the secretions exhibited pH optima between 4.5 and 5.0, and temperature optima at either 60 or 70oC. Using non-linear regression fit analysis, Vmax values ranged from 6.4 - 291 ug 30 min-1, while Km values ranged from 0.51 to 660 uM. The β-glucosidase activity in extracts showed significant but negative correlations with carbohydrate content.

This information will constitute part of the fundamental basis for selecting WRF that could be used individually or in combination with other organisms, for bioconversion of biomass to fermentable sugars and other bio-product.