Effects of a nonionic surfactant on the behavior of Bacillus amyloliquefaciens α-amylase in the hydrolysis of malto-oligosaccharide

摘要

The effects of a nonionic surfactant, polyoxyethylene mono-N-dodecyl-ether (Brij 35; number of units of ethylene oxide moieties, 23), on the behavior of Bacillus amyloliquefaciens α-amylase in the hydrolysis of maltoheptaose were studied at 25°C and pH 7.0. The addition of the surfactant to the enzyme-substrate system increased the amount of reducing sugars during the hydrolysis. A high-performance liquid chromatography technique was used for the determination of the hydrolysis products. During the hydrolysis, the concentration of maltose was increased by the addition of the surfactant, whereas the concentrations of other products were unchanged. Therefore, the increase in the amount of reducing sugars was thought to be due to the increase of the maltose fragment. Because the transglycosylation of hydrolyzed maltose takes place during the hydrolysis, the suppression of transglycosylation accelerates the production of total reducing sugars. The interaction between the maltose fragment and micelle surface might induce the release of this fragment from the enzyme active site and then suppress the transglycosylation. The bindings of the enzyme, the substrate, and/or the products to the micelle surface may affect the hydrolytic behavior including both the hydrolysis and transglycosylation catalytic conversions.