alpha-Galactosidase was immobilized in calcium alginate in the presence of glutaraldehyde. The optimum pH of the soluble enzyme was 4.8, whereas that of the immobilized enzyme was 4.5. The optimum temperature of the soluble enzyme was 50degreesC and that of the immobilized enzyme was increased to 57 degreesC. The immobilized enzyme retained its activity for a longer period. The immobilized enzyme exhibited higher K-m and lower V-max compared to the soluble enzyme. Immobilized alpha-galactosidase was used in batch, repeated batch and in continuous mode. After 12 h, soluble and immobilized enzyme resulted in 93 and 8 1 % reduction in raffinose family oligosaccharide content in soymilk. Immobilized calcium alginate beads were used for repeated hydrolysis at 50degreesC and showed good operational stability. The performance of immobilized a-galactosidase was also tested in a fluidized bed reactor at different flow rates and 90% reduction of raffinose family oligosaccharides in soymilk was obtained at 40 ml h(-1) flow rate. (C) 2004 Elsevier Ltd. All rights reserved.