Stabilization of enzymes is one of the major challenges in biocatalytic processes. Alpha amylase from Bacillus amyloliquefaciens was immobilized as a cross-linked enzyme aggregates (CLEAs). Alpha amylase was aggregated using ammonium sulfate. The resultant aggregates on cross-linking with glutaraldehyde produced insoluble catalytically active cross-linked enzyme aggregates. The effects of precipitation and cross-linking were studied and immobilized alpha amylase was characterized. 70% ammonium sulfate saturation, 2 %( v/v) glutaraldehyde, were used; 6 h cross-linking reaction at room temperature was performed and 100% activity recovery was achieved in CLEAs with enhanced thermal and acidic condition stabilities. The cross-linked enzyme aggregates exhibited pH optima of 6.0 and higher temperature optima of 60°C. Although after immobilization maximum velocity of enzyme reaction did not change, substrate affinity of the enzyme increased. Alpha amylase CLEAs retained 65% activity after 4 reuses with 30 min of each reaction time. The Scanning electron microscopy analysis showed that morphology of CLEAs substantially changed after 4 reuses.