This study was carried out to determine the growth and production of amylase by Aspergillus chevalieri in a defined medium. A. chevalieri was grown in a synthetic medium containing starch as the sole carbon source. Culture filtrate exhibited amylase activity. Optimum enzyme activity was observed on the tenth day of incubation. The presence of NaCl and MgCl 2 stimulated amylase activity while EDTA and HgCl 2 in the reaction mixture caused a reduction in the activity of the enzyme. The activity of the enzyme was optimum at 35 o C and pH 6.5. The amylase of Aspergillus chevalieri was heat labile, losing its activity completely after twenty minutes of heating at 70 o C. The amylase produced by this fungus is of significance in the brewing industry and pharmaceuticals. The observed properties would aid in preserving the enzyme and knowing optimum conditions for activity to assist in maximizing industrial output.

In an attempt to enhance the industrial production of α-amylases in the tropics, sterile fresh bread was inoculated with spore suspensions of Penicillium citrinum at 25 o C. Extracellular α-amylases were produced and subjected to partial purification by ammonium sulphate precipitation and dialysis. Further purification by gel filtration and ion-exchange chromatography was engaged. The molecular weights of the α-amylase fractions obtained and estimated by gel filtration using Sephadex G-100 were approximately 56,234 Daltons, 53,089 Daltons and 11,885 Daltons. The apparent Michalis-Menten constant (K m) values for the hydrolysis of starch by the purified α-amylase fractions were approximately 8.3 mg/ml, 10 mg/ml and 7.14 mg/ml respectively. Optimum activities were at 30 o C for one of the fractions and 35 o C for the other two fractions and were at pH 5.5 and pH 6.0. The activities of the α-amylase fractions produced by the fungus were stimulated at varying degrees by NaCl, KCl, CaCl 2 and MgCl 2 but inhibited by Ethylene Diamine Tetraacetic Acid (EDTA), mercuric chloride (HgCl 2) and 2,4-dinitrophenol (DNP). The α-amylase fractions were sensitive to heat, losing all their activities within twenty minutes of heating at 80 o C. The industrial production of α-amylases should be encouraged in the tropics using bread as a cheap source of substrate.

No abstract

A mutant of Aspergillus niger induced by ultraviolet radiation of a strain of a tropical wild type (Aspergillus niger IFE 08) expressed α-amylase activity in a defined medium with starch as carbon source and ammonium chloride as nitrogen source of growth and development. The enzyme was subjected to partial purification by ammonium sulphate precipitation followed by dialysis. Specific activity of the enzyme increased 1.71 fold while recovery was 29.9% after dialysis.

No abstract