Hydrolysis of casein catalyzed by papain in n-propanol/NaCl two-phase system

Abstract

Enzymatic hydrolysis of casein to produce free amino acids by papain was performed in a kind of novel two-phase system, which was composed of n-propanol, NaCl and water. The phase diagram of the two-phase system was plotted. In this system, top phase contained more n-propanol and bottom phase contained more NaCl and water. Papain and casein were mainly distributed in bottom phase, and free aromatic amino acids (tyrosine, tryptophan and phenylalanine) produced by enzymatic hydrolysis were mainly in top phase. When the two-phase system consisted of 44% n-propanol, 60g/l NaCl, 0.15g/l papain and 13g/l casein at 55°C and pH 5.6, the transformation yield was 99.5%, which was higher than those of n-propanol/water single phase, aqueous single phase, n-hexane/water two-phase system and PEG/phosphate two-phase system. The novel two-phase system is practically applicable to some enzymatic reaction, if the substrates and products have different partition coefficients.