The preference of the lipase Candida antarctica lipase B for dicarboxylic acids of a specific chain length has been demonstrated. The C6 adipic acid was found to be the preferred substrate as measured by the specificity constant for the esterification reaction. The effect of substitution on the substrate has been investigated and the carbonyl of 2-oxoadipic acid shown to stall the esterification reaction most probably by unfavourable hydrogen bonding within the active site of the enzyme. (C) 2004 Elsevier Inc. All rights reserved.