Use of Tropical Strains: Aspergillus vadensis and Aspergillus oryzae as Producers of α-Amylases in Biotechnological Practice

Enzymes especially α-amylases are imported into Nigeria, West Africa in tons from the United States of America, Asia and East Europe, cumulating into annual national debts because of the dwindling exchange rate in foreign funds. There is avenue for the production of this enzyme locally in the tropics and even in the temperate zones of the world since production of this enzyme is advocated. In our study the isolates were obtained from deteriorated barley (Hordeum vulgare L.) plants grown locally in Jos, Plateau State, Nigeria. Tropical strains of Aspergillus vadensis and Aspergillus oryzae were isolated from deteriorated barley seeds placed onto potato dextrose agar slants and plates at 25oC. Sterile barley-seed medium (1% w/v) and a defined growth medium consisting MgSO4.7H20, K2HPO4, KH2PO4 , aspartic acid, biotin, thiamine and FeSO4.7H2O with a nitrogen source and a carbon source for fungal growth were inoculated with spore suspensions of approximately 5 x 106 spores per ml of one hundred and twenty-hour-old cultures of each isolate. Incubation was at 25°C. The carbon source was varied and was independently starch, maltose, sucrose, lactose, glucose or galactose when the nitrogen source was potassium nitrate. The nitrogen source was also varied and was independently ammonium chloride, urea, potassium nitrate, ammonium sulphate, glycine, sodium nitrate, tryptone or peptone, when the carbon source in the growth medium was starch. Extracellular proteins produced within a ten day incubation period were extracted and assayed for α-amylase activity using the Pfueller and Elliott (1969) method. Extracellular proteins with expression of α-amylase activities were produced by the tropical fungal strains: Aspergillus vadensis and Aspergillus oryzae grown on the barley-seed medium and the defined growth medium used in this investigation within a period of ten days at 25°C. For the production of the most active α-amylases, the best carbon sources were maltose and glucose while the best nitrogen sources were ammonium chloride and ammonium sulphate when fungal strain Aspergillus vadensis was used as an inoculum. However, the best carbon sources were barley-seed medium, starch and sucrose while the best nitrogen sources were urea, glycine and sodium nitrate when the fungal strain Aspergillus oryzae was used as an inoculum. The exploration of this innovative is an a venue for the industrial production of α-amylases. This is encouraged in tropical Nigeria, West Africa, Ukraine, and East Europe.