ABSTRACT
Four α-amylases and two glucoamylases from various sources, in eight combinations, were used to study the synergistic hydrolysis of crude corn starch at various temperatures. At 40 and 50°C, the combinations containing Rhizopus mold glucoamylase enhanced hydrolysis of corn starch compared wth that obtained with the combinations from Aspergillus niger. At 60°C, Rhizopus mold combinations gave low reaction yields as the enzyme was inactivated. The differences observed between α-amylases are smaller, with the exception of Bacillus licheniformis α-amylase, which presented more than twice the productivity of the other α-amylases, at all temperatures. In terms of substrate conversion at 5 hr of hydrolysis, the combination of B. licheniformis α-amylase with Rhizopus mold glucoamylase at 50°C presents 76% substrate conversion, whereas, with all the other combinations, starch conversion was 13–73%. HPLC analysis of the reaction products obtained at 50°C showed that the main product of corn starch hydrolysis was glucose at 85–100%. Further experiments showed that A. niger glucoamylase and B. licheniformis α-amylase were the only enzymes that retained their initial activity after incubation at the temperatures studied.
