Activity and stability of soluble and immobilized α-glucosidase from baker's yeast in cosolvent systems

The activity of alpha-glucosidase from baker's yeast was determined in various concentrations of dioxan, tetrahydrofuran, tert-butanol, dimethylformamide, methanol and dimethylsulfoxide (DMSO). Higher activities were observed with sucrose than with nitrophenylglucoside as substrate in cosolvent mixtures. In 30% (v/v) DMSO, 25% of the activity obtained in pure water was detected, and in 30% (v/v) methanol 12.5% of the activity in pure water was detected, while in other cosolvents there was almost no activity under these conditions. alpha-glucosidase was immobilized onto a macroporous copolymer of ethylene glycol dimethacrylate and glycidyl methacrylate, poly(GMA-co-EGDMA), by the glutaraldehyde method. By immobilization, the half-life of the enzyme in 35% (v/v) methanol was increased from 6 to 60min and from 4 to 15min in 45% (v/v) DMSO. The activity of the immobilized enzyme in 30% (v/v) DMSO and 30% (v/v) methanol was 22% and 18% of the activity in pure water, respectively.