Active enhanced isolates producing high levels of amylolytic enzymes were obtained by gamma irradiation of the wild type Aspergillus nigerF-909. The potent isolate No. 44e was derived from 0.8 kGy treated group grown on radicle (a waste of malt beverage industry) containing medium under solid state fermentation (SSF) conditions. The potent isolate exhibited enhanced production of alpha-amylase (EC 3.2. 1.1), glucoamylase (EC 3.2. 1.3) and alpha-glucosidase (EC 188.8.131.52), with relative increase in activities over the parental strain as reaching 111.3, 117.4 and 140% respectively. A study was conducted on this isolate to assess the effect of supplementation of radicle medium with low levels of five surfactants namely Tween 20, Tween 40, Tween 60, Tween 80 and Triton X-100 and four plant oils i.e. cotton seed, maize, soybean and sunflower on the enzymes synthesis under SSF conditions. The enzyme levels were considerably increased in the presence of Tween 80 at level 0.2% (v/v). Several solvent systems were evaluated with respect to their extraction abilities of the fungus amylolytic enzymes grown on the solid state culture. The most efficient extracting solvent proved to be tap water adjusted to pH 3.5. Furthermore, the extraction temperature, contact time and shaking speed affected the extraction process. Purification folds of 10.2, 10.4 and 11.9 for alpha-amylase, glucoamylase and alpha- glucosidase were obtained by partial purification through precipitation with 65% saturation ammonium sulphate. Application studies were carried out on the partially purified enzyme of the potent isolate No. 44e which was used to hydrolyze native raw starch as a substrate wherein about 97% saccharification for 20% slurry of raw potato starch was achieved after 14h. Furthermore, and in complementary experiments 8.6% (v/v) ethanol yield was produced from 18% (w/v) starch hydrolyzate when -fermentation studies were carried out with Saccharomyces cerevisiaeafter 24h at 36°C. Yeast biomass of 21.3 gL-1 was produced when the culture conditions using the starch hydrolyzate were modified to obtain microbial protein production.
Fadel M. and A. I. El - Batal , 2000. Studies on Activation of Amylolytic Enzymes Production by Gamma Irradiated Aspergillus niger Using Some Surfactants and Natural Oils under Solid State Fermentation . Pakistan Journal of Biological Sciences, 3: 1762-1768.