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

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