Comparative study of hydrolysis of various starches by alpha-amylase and glucoamylase in PEG-dextran and PEG-substrate aqueous two phase systems

摘要

Crude rice, corn [maize], wheat, barley, potato and soluble starches were hydrolysed by the synergistic action of alpha-amylase and glucoamylase [glucan 1,4-alpha-glucosidase] in PEG-dextran and PEG-substrate aqueous 2-phase systems. The hydrolysisproducts at different temperatures (30-80deg C) were determined by the chromatometric method of phenol-sulfuric acid and by HPLC. Glucose production from potato and soluble starch was very low at 30deg C, only maize and rice starches giving higher glucose concentrations at this temperature. With the exception of maize starch, glucose production from all starches increased as the temperature increased up to 70deg C. At 70deg C, glucose production was highest from soluble and potato starches and lowest from maize starch. The use of the PEG-dextran system to carry out the enzymatic hydrolysis of starch had the advantage of separating the product in the PEG phase, while all the other materials remain in the dextran phase. Nevertheless, the cost of the two water-soluble polymers, especially dextran, is a prohibiting factor for industrial use of this biphasic system. Gelatinization of the starch prior to hydrolysis gave higher yields of glucose than non-gelatinized starch and the separation of the phases was satisfactory.