Relationship between bacterial density and chemical composition of a tropical sewage oxidation pond

Studies were carried out to examine the performance of the sewage oxidation pond situated in and serving the community of the Obafemi Awolowo University, Ile-Ife, Nigeria. A survey of the coliform and total bacterial populations was carried out. The sewage was also examined for biochemical oxygen demand, dissolved oxygen content as well as for nitrate, phosphate, silica and chloride contents. The mean coliform bacteria counts decreased gradually from 69.1×105 per 100 ml to about 10.1×105 per 100 ml as the sewage moved through the oxidation pond into the receiving stream. A similar decrease in mean biochemical oxygen demand of the sewage from 397.8 Ib/acre/day to 64.2 Ib/acre/day was also observed. The concentrations of nitrate, phosphate and chloride decreased from the pond influent to the pond effluent. On the other hand, both the silica and dissolved oxygen content of the sewage gradually increased from 14.1 to 19.0 mg/l and 8.1 to 13.9 mg/l respectively, across the pond to the effluent. The coliform and total bacterial counts as well as the concentrations of most of the chemicals in the receiving stream increased after being joined by the sewage oxidation pond effluent. It is therefore concluded that the receiving stream was subject to both bacteriological and chemical pollution. Building of additional oxidation ponds or addition of a primary sewage treatment to the existing system is recommended for more efficient wastewater treatment.Key words: Bacterial density, chemical composition, oxidation pond, sewage, tropics

Expression and characterization of α-Amylases from penicillium citrinum with bread as growth substrate

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 oC. 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 (Km) 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 oC for one of the fractions and 35 oC 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, CaCl2 and MgCl2 but inhibited by Ethylene Diamine Tetraacetic Acid (EDTA), mercuric chloride (HgCl2) and 2,4-dinitrophenol (DNP). The α-amylase fractions were sensitive to heat, losing all their activities within twenty minutes of heating at 80 oC. The industrial production of α-amylases should be encouraged in the tropics using bread as a cheap source of substrate.Keywords: α-Amylase, expression, bread, purification, characterization

Amylase activity in culture filtrate of Aspergillus chevalieri

This study was carried out to determine the growth and production of amylase by Aspergilluschevalieri 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 MgCl2 stimulated amylase activity while EDTA and HgCl2 in the reaction mixture caused a reduction in the activity of the enzyme. The activity of the enzyme was optimum at 35oC and pH 6.5. The amylase of Aspergillus chevalieri was heat labile, losing its activity completely after twenty minutes of heating at 70 oC. 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.Keywords: Amylase production, Aspergellus chevalieri, enzyme, brewing industry, pharmaceuticals