Bioconversion of p-methoxyphenylacetonitrile (MOPAN) to p-methoxyphenylacetic acid (MOPAA) by immobilized cells of Bacillus subtilis ZJB-063, a nitrilase producing strain, was investigated in batch and repeated batch. Four entrapment matrixes were screened to search for a suitable support in terms of enzyme activity and reusability of the bead, and alginate exhibited significant process advantages over its other counterparts. The effects of sodium alginate concentration, bead diameter, CaCl2 concentration were examined. Maximum activity was achieved when the above parameters were set as 2.5% sodium alginate, 2 mm of bead diameter, 4.0% CaCl2. An initial MOPAN concentration of 10 mM was completely converted to MOPAA by entrapped cells after 8 h reaction under the optimized conditions. Efficient reusability of the biocatalyst up to nine batches was achieved by immobilization, and treatment with polyethyleneimine (PEI) and glutaraldehyde (GA) further extended the longevity to 18 batches. (C) 2008 Elsevier Ltd. All rights reserved.