Affinity precipitation could be a viable alternative to conventional protein purification techniques with advantages of easy scale-up, cost and time effectiveness. We have used alginate as the affinity matrix for entrapment of alpha-amylase and subsequent precipitation of the beads with calcium chloride. Amylase was recoverable by addition of 0.5 M NaCl containing 0.2 M Ca2+. The enzyme was found to be homogenous (recovery of 76%) with a specific activity of 1764 U/mg. The pH and temperature optima shifted (on entrapment) from 5.5 to 6.0 and 54 to 60 degrees C, respectively. The entrapped enzyme had higher thermal stability compared to the free enzyme. The midpoint of thermal inactivation for the enzyme increased by 6 +/- 1 degrees C on entrapment. The entrapped enzyme had an E-a value of 51.7 compared to 40.9 kcal mol(-1) for the free enzyme. The positive increase in E-a value as well as the half-life of the entrapped enzyme is indicative of increased stability. The reusability of the beads was dependent on bead size. Beads with < 1 mm were stable and could be reused for six cycles with similar to 30% loss in activity. (c) 2006 Elsevier Ltd. All rights reserved.