Substrate conversion with an enzyme immobilized on an ultrafiltration membrane

A process is disclosed for chemically converting a substrate into its reaction products and immediately thereafter physically separating the reaction products in a continuous operation. The process is carried out with a bioreactor having an ultrafiltration membrane containing an immobilized chemical agent which is preferably an enzyme. The bioreactor is prepared by securing an ultrafiltration membrane to an inside wall of a porous tubular support and chemically bonding an enzyme to an inner surface of the membrane. The enzyme is preferably bonded to the membrane by chelation and the membrane may be a polymeric membrane or a metal oxide membrane. To convert a substrate, a substrate-containing feed stream is preferably flowed tangentially along the inner surface of the membrane containing the immobilized enzyme. Sufficiently small reaction products filter through pores of the membrane and larger reaction products are retained by the membrane. In a preferred embodiment, contacting of fresh fruit juice with pectinase immobilized on the membrane results in pectinase treatment or the juice and immediate extraction and clarification of the juice. In another embodiment, the enzyme immobilized is glucoamylase and corn dextrins are converted to reducing sugars