Solubility and selective crystallization of lactose from solutions of its hydrolysis products glucose and galactose

Abstract

A high degree of conversion is desired when lactose is hydrolyzed to glucose and galactose. This produces, however, a high concentration of galactose, which is inhibitory for the enzyme catalyst (beta-galactosidase). The inhibition can be reduced by limiting the conversion per pass over the enzyme (e.g. to ca. 50%), separating unconverted lactose from the reactor effluent, and recycling it to the reactor inlet. (This allows the overall conversion to be raised to ca. 80-90%). The solubilities of lactose, glucose, and galactose have been determined at various temperatures and for sugar mixtures having different concentrations and degrees of hydrolysis. Various cooling crystallizations have defined convenient and simple processes for the selective separation of lactose from its hydrolysis products.