Journal of Membrane Science, Vol.570, 436-444, 2019
Improved antifouling properties of polyethersulfone membranes modified with alpha-amylase entrapped in Tetronic (R) micelles
A novel method of polyethersulfone membrane modification with alpha-amylase entrapped in polymeric micelles is proposed to improve the antifouling properties of membranes. The immobilization of alpha-amylase is performed by its incorporation into micelles based on commercial polymeric surfactants (Tetronic (R)-701 and Tetronic (R)-90R4) with their subsequent adsorption on the membrane surface. The size of micelles loaded with enzyme depends on the nature of the surfactant and is equal to 400 and 100 nm for Tetronic (R)-701 and Tetronic (R)-90R4, respectively. Biocatalytic activity and membrane stability in the process of starch ultrafiltration are discussed in the paper. The optimal pH was found to be 6.5-7.5 for Tetronic (R)-701 and 6.0-6.5 for Tetronic (R)-90R4 micelles. The activity of enzyme entrapped in the micelles, adsorbed on the membrane surface, increased 1.5-1.8 times. The starch conversion rate of 80-90% was observed for membranes with immobilized alpha-amylase. The biocatalytic activity of immobilized enzyme was maintained at a high level during five cycles of regeneration. Moreover, the layer of micelles with incorporated alpha-amylase on the membrane surface reduced the effect of concentration polarization due to starch hydrolysis. The micelle immobilization caused hydrophilization of the surface and an increase in the number of bound water molecules which prevented the formation of a cake in the boundary layer.