Studies on Enzymatic Liquefaction and Saccharification of Starch

Liquefaction of corn starch is generally considered to be difficult to achieve. A double enzyme system, a combination of bacterial alpha-amylase and fungal glucoamylase, was tested for the production of dextrose from corn starch. The former liquefies starch and the latter hydrolyzes further into glucose

Particularly various conditions for liquefaction of corn starch were examined. As criteria of solubilization of starch molecule, turbidity of filtrate obtained while the solution was hot, iodine coloration value, filterability and turbidity of the saccharified solution after the addition of alcohol were measured.

Starch slurry containing bacterial alpha-amylase was poured continuously in fine stream into hot water with vigorous agitation. Liquefaction at 92°C was better than at 87°C for dissolving corn starch. It was indispensable to apply heat treatment under high pressure after liquefaction followed by the second addition of bacterial alpha-amylase at 90°C to render remaining tightly bound starch micelle to be broken down. Heat treatment was continued at 120°C or at higher temperature. Then, solution was cooled rapidly down to about 90°C. Immediately bacterial alpha-amylase was added. In case the second addition of bacterial alpha-amylase was carried out after cooling to 55°C or after holding for 10min at 80°C, no effect was observed by the second addition. These findings were confirmed in the experiments on commercial production scale.