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

Aspergillus niger ITV-01 presents amylolytic activity, identified as alpha-glucosidase, an enzyme that only produces alpha-D-glucose from soluble starch and that presents transglucosylase activity on alpha-D-glucopyranosyl-(1-4)-alpha-D-glucopyranose (maltose) (200-gL(-1)). Biochemical characterization was performed on A. niger ITV-01 alpha-glucosidase; its optimum parameters were pH 4.3, temperature 80 degrees C but stable at 40 degrees C, with an energy of activation (Ea) 176.25 kJ mol(-1). Using soluble starch as the substrate, K-m and V-max were 5 mg mL(-1) and 1000 U-mg(-1), respectively. As alpha-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 75 kDa. 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 alpha-D-glucopyranosyl-(1-4)-alpha-D-glucopyranose (maltose).