Evidence of high production levels of thermostable dextrinizing and saccharogenic amylases by Aspergillus niveus

Abstract

The aim of this work was to analyze the effect of several nutritional and environmental parameters on amylase production by a novel, isolated from the thermotolerant filamentous fungus Aspergillus niveus. This strain produced high levels of amylolytic activity in Khanna liquid medium supplemented with commercial starch, initial pH 6.5, under static conditions for 72 h. Among the tested carbon sources, milled corn, oatmeal, soluble potato starch and maisena were the best inducers of enzymatic secretion (220, 180, 170 and 150 U/mL), respectively. The main products of hydrolysis analyzed by thin layer chromatography were glucose, maltose and traces of maltooligosaccharides, suggesting the presence of α-amylase and glucoamylase activities in the crude extract. The optimal pH were 4.5 and 5.5 and the optimum temperature was 65°C. The enzymes were fully stable up to 1 h at 55°C. It was possible to verify the presence of three bands with amylolytic activity in non-denaturing polyacrylamide gel electrophoresis (PAGE). These aspects and other properties suggested that the amylases produced by A. niveus might be suitable for biotechnological applications.
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Keywords: Starch, α-amylase, glucoamylase, Aspergillus niveus, submerged fermentation, thermostability

African Journal of Biotechnology Vol. 12(15), pp. 1874-1881