Production and biochemical characterization of α-glucosidase from Aspergillus niger ITV-01 isolated from sugar cane bagasse.

Abstract

Aspergillus niger ITV-01 presents amylolytic activity, identified as α-glucosidase, an enzyme that only produces α-d-glucose from soluble starch and that presents transglucosylase activity on α-d-glucopyranosyl-(1-4)-α-d-glucopyranose (maltose) (200 gL-1). Biochemical characterization was performed on A. niger ITV-01 α-glucosidase; its optimum parameters were pH 4.3, temperature 80°C but stable at 40°C, with an energy of activation (Ea) 176.25kJmol-1. Using soluble starch as the substrate, Km and Vmax were 5mgmL-1 and 1000 U mg-1, respectively. As α-glucosidase is not a metalloenzyme, calcium and EDTA did not have any effect on its activity. The molecular weight was estimated by SDS-PAGE to be about 75kDa. It was also active in methanol and ethanol. When ammonium sulfate (AS) and yeast extract (YE) nitrogen sources and calcium effect were evaluated, the greatest activity occurred using YE and calcium, as opposed to AS media where no activity was detected. The results obtained showed that this enzyme has industrial application potential in the processes to produce either ethanol or malto-oligosaccharides from α-d-glucopyranosyl-(1-4)-α-d-glucopyranose (maltose).