Lactose Hydrolysis by β-Galactosidase in Aqueous Two-Phase Systems

概要

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lactose hydrolysis was studied in aqueous two-phase systems with β-galactosidases from bacteria(Escherichia coli), yeast (Saccharomyces fragillis), and fungi (Aspergillus oryzae). Salts such as potassium phosphate, ammonium sulfate, and sodium citrate used at concentrations forming phase systems could severely inhibit β-galactosidase activity from yeast and inhibit E. coli enzyme activity to a lesser extent, but had no effect on fungal β-galactosidase activity. Polymers such as polyethylene glycol (PEG) and a modified starch (Reppal PES) could increase the enzyme activity toward hydrolyzing o-nitrophenyl-β-D-galactopyranoside. E. coli β-galactosidase showed a partition coefficient of 127 in a PEG/Reppal PES system to provide an efficient system for carrying out extractive hydrolysis of lactose. A. orizae β-galactosidase showed a partition coefficient of 0.0042 in a PEG/sodium citrate system. Continuous hydrolysis of lactose in this system with a mixer-settler enzyme reactor could be operated for a period of 84 h with only 10% loss of enzyme activity. Slower reaction rates in two-phase systems than in buffer systems may arise from preferential distributions of both enzyme and inhibitory products into the same phase.
公益社団法人日本生物工学会の論文
1991-03-25