MYCELIA-ASSOCIATED BETA-XYLOSIDASE IN PELLETS OF ASPERGILLUS SPS

A screening of 10 strains of Aspergillus for pellet formation and mycelia-associated beta-xylosidase activity was performed in media containing glucose and glucose supplemented with methyl beta-D-xylopyranoside. The aim was to produce an immobilized enzyme preparation. Three strains with high mycelia-associated beta-xylosidase activity were investigated for enzyme leakage and enzyme stability: A. terreus QM 1991, A. phoenicis ATCC 13157, and A. phoenicis QM 329. The pellets of A. phoenicis QM 329 had the highest beta-xylosidase activity (280 IU/g dry wt mycelia) after 333 h of incubation. From measurements of both cell-bound enzyme activity and the activity in solution, it could be concluded that for Aspergillus phoenicis QM 329 and ATCC 13157 the decrease in beta-xylosidase activity bound to the pellets was owing to enzyme leakage. For Aspergillus terreus QM 1991, the decrease of pellet-bound beta-xylosidase activity was the result of both leakage and enzyme deactivation at 50-degrees-C. beta-Xylosidase in pellets of A. phoenicis QM329 hydrolyzes xylobiose and p-nitrophenyl beta-D-xylopyranoside with the same rate of conversion.