Changes in alpha-and beta-amylase activities during seed germination of African finger millet

Abstract

Changes in α - and β -amylase activities in African finger millet (Eleusine coracana (L) Gaertener) were followed during germination. Germination on a small scale was performed at 15°C for 1-10 days and at 20, 25 and 30°C for 1-8 days. α- and β-Amylase activities in malt crude extracts of germinated finger millet were evaluated spectrophotometrically using chromogenic methods. The highest α-amylase activity was exhibited in malt flour of finger millet germinated at 15°C for 9 days and at 20°C for 6 days, while the highest β-amylase activity was displayed in the malt flour germinated for 5 days at 30°C. Thermo-stability of these enzymes in malt extracts was also evaluated. Malt extracts incubated at 40 and 50°C for up to 4 h retained about 84 and 64% of α-amylase activities, respectively. There was a substantial decrease in α-amylase activity to more than 90% when malt extracts were incubated at 70 and 90°C for 40 and 10 min, respectively. β-Amylase was completely inactivated when the crude extract was incubated at 70°C for only 10 min. At pH 5.4, α-amylase displayed maximum catalytic activity at around 45°C. Optimum temperature for β-amylase activity at pH 6.0 was between 50 and 55°C. Activity staining for α-amylase was also performed and three bands of activity were found in malt extract, each possibly representing an isozyme of α-amylase from finger millet.