Studies on glucoamylase produced from Aspergillus awamori (NRRL-3112) and their effect on saccharification of potato starch.

Efficiency of an enzymatic starch saccharification process depends not only on the activity of the glucoamylase but also its purity. About 96.82% unwanted proteins present in 2-day old culture broth of A. awamori NRRL-3112 (grown in MYGP medium) were separated by precipitation with ammonium sulphate which was followed by dialysis. More than 80% activity of the glucoamylase was recovered. Three protein fractions (A, B, C) were identified using gel permeation chromatography. Fractions A and B showed comparatively higher glucoamylase activity than fraction-C. Moreover, fraction-B showed no product inhibition. The optimum temperature and pH of the purified enzyme (fraction-B) were 60 degrees C and 4.0 respectively. The saccharification efficiency of potato pulp was more in case of using purified glucoamylase (fraction-B) as compared to that of crude enzyme.

Immobilization of amyloglucosidase.

Enzymatic hydrolysis of starch for the production of glucose syrups of various compositions has assumed considerable commercial significance due to the extensive application of these syrups in food and beverage industries. Hydrolysis of starch to glucose involves liquefaction of the gelatinized starch with acid or thermostable alpha-amylase followed by saccharification to glucose by amyloglucosidase. Large scale saccharification of liquefied starch to glucose using soluble enzyme is time consuming and requires 48-72 hr at pH 4.5 and 55-60 degrees C. Since, by replacing soluble amyloglucosidase with immobilized enzyme, it is possible to reduce the conversion time, several methods have been tried to obtain a highly active and stable immobilized preparation capable of converting high concentrations of liquefied starch to glucose. However, till today, immobilized amyloglucosidase has not found industrial application as no immobilized system has shown high temperature stability and conversion efficiency comparable to that of the soluble enzyme.