Synergistic hydrolysis of crude corn starch by alpha-amylases and glucoamylases of various origins

Four alpha -amylases and two glucoamylases from various sources, in eight c ombinations, were used to study the synergistic hydrolysis of crude corn st arch at various temperatures. At 40 and 50 degreesC, the combinations conta ining Rhizopus mold glucoamylase enhanced hydrolysis of corn starch compare d wth that obtained with the combinations from Aspergillus niger. At 60 deg reesC, Rhizopus mold combinations gave low reaction yields as the enzyme wa s inactivated. The differences observed between alpha -amylases are smaller , with the exception of Bacillus licheniformis alpha -amylase, which presen ted more than twice the productivity of the other alpha -amylases, at all t emperatures. In terms of substrate conversion at 5 hr of hydrolysis, the co mbination of B. licheniformis alpha -amylase with Rhizopus mold glucoamylas e at 50 degreesC presents 76% substrate conversion, whereas, with all the o ther combinations, starch conversion was 13-73%. HPLC analysis of the react ion products obtained at 50 degreesC showed that the main product of corn s tarch hydrolysis was glucose at 85-100%. Further experiments showed that A. niger glucoamylase and B. licheniformis alpha -amylase were the only enzym es that retained their initial activity after incubation at the temperature s studied.