Advances in Biochemistry 2015; 3(1): 15-23 Published online February 9, 2015 (http://www.sciencepublishinggroup.com/j/ab) doi: 10.11648/j.ab.20150301.14 ISSN: 2329-0870 (Print); ISSN: 2329-0862 (Online) Biochemical Characterization of Crude α-Amylase of Aspergillus spp. Associated with the Spoilage of Cassava (Manihot esculenta) Tubers and Processed Products in Nigeria Oghenetega Jonathan Avwioroko * , Nyerhovwo John Tonukari, Samuel Ogheneovo Asagba Department of Biochemistry, Faculty of Science, Delta State University, Abraka, Nigeria Email address: joavwioroko@gmail.com (J. O. Avwioroko), tonukari@gmail.com (N. J. Tonukari), asagbabch@yahoo.com (S.O. Asagba) To cite this article: Oghenetega Jonathan Avwioroko, Nyerhovwo John Tonukari, Samuel Ogheneovo Asagba. Biochemical Characterization of Crude α- Amylase of Aspergillus spp. Associated with the Spoilage of Cassava (Manihot esculenta) Tubers and Processed Products in Nigeria. Advances in Biochemistry. Vol. 3, No. 1, 2015, pp. 15-23. doi: 10.11648/j.ab.20150301.14 Abstract: In this research, crude α-amylases associated with the spoilage of cassava (Manihot esculenta) tubers/ product (‘eba’) were biochemically characterized. They were isolated from five fungi: Aspergillus sp. CSA25, Aspergillus sp. CSA26, Aspergillus sp. CSA27, Aspergillus sp. CSA35 and Aspergillus sp. CSA38. The results of the analyses showed that the activities of α-amylase obtained from both sources (cassava tuber/ eba) were optimal at 45°C and pH 5.0. The maximum specific activity (Vmax) of the enzyme was found to be 10 U/mg protein, while its Michaelis-Menten constant (Km) was between 0.37 -1.25%w/v. The α-amylase is thermally stable for 1 - 2 h at optimum temperature and pH (45°C; pH 5.0). A broad range of substrate specificity was expressed by the enzyme for cassava starch-containing products (tapioca flour, garri flour, cassava flour, 1%, w/v); however, potato (Ipomoea batatas) starch, yam (Dioscorea rotundata) flour and cocoyam (Colocasia esculenta) flour were relatively minimally hydrolyzed by the crude α-amylases obtained from Aspergillus spp. that caused spoilage of cassava. Ethylenediamine tetraacetic acid (1 mM EDTA) and Mg 2+ treatment had no significant (p > 0.05) effect on the activities of the amylase, but Na + , K + , Ca 2+ , Fe 3+ , thiourea and 5′,5′-dithiobis-2-nitrobenzoate (1 mM DTNB) enhanced its activities. The fungal α-amylases were most activated by K + and had a salt tolerance of 1 - 2 M NaCl for 24 h. The fungal α-amylases reported in this study would find useful application in industries like food industry, detergent industry, paper industry, textile industry, pharmaceutical industry, etc where microbial α-amylases would be required for efficient and cost-effective hydrolysis of cassava starch, cassava flour and or its products. Keywords: Manihot esculenta (Cassava), Aspergillus spp., α-Amylase, Biochemical Characterization 1. Introduction Alpha amylase (E.C 3.2.1.1) is an extracellular enzyme that catalyzes the hydrolysis of α -D-(1, 4) glycosidic linkages in starch components and related polysaccharides to release maltose, a disaccharide [31, 29, 46]. The enzyme is also referred to as 1,4-α-D-glucan- glucanohydrolase. It is a key enzyme in the production of starch derivatives and has also found reputable application in fabrics designing industries, baking industry, pharmaceuticals and detergents making industries [22, 37]. At present, a renewed interest in the exploration of the enzymatic activity of extracellular enzymes like amylases in several microorganisms has been stimulated in the mind of many research workers that look forward to using such microorganisms as biotechnological sources of industrially relevant enzymes [38, 41, 46, 23, 3]. Most plants, bacteria, fungi and even animals have been severally reported to secrete a number of industrial enzymes like amylases [43, 9, 22]. Generally, fungi are a group of microorganisms known to grow on substrates to which they can easily secrete digestive enzymes. They have been found growing on foods like rice, bread, cooked garri (a cassava product), cooked yam (Dioscorea rotundata), and even on leather materials (fabrics) undergoing spoilage. Manihot esculenta (cassava), a