The asymmetric microbial reduction of phenylglyoxylic acid (PGA) to (R)-mandelic acid ((R)-MA) with immobilized Saccharomyces cerevisiae cells on globular chitosan was studied. The immobilization conditions and characterization of the immobilized cells were carried out. Chitosan-acetic acid solution was injected into a mixture of 20% NaOH and 30% CH(3)OH aqueous solution to obtain globular chitosan, and then the globular chitosan was treated with 1% solution of glutaraldehyde to immobilize yeast cells, which were used to synthesize (R)-MA. The optimum conditions were identified as the substrate concentration of 10 mmol L(-1), pH of 6.5 and reaction temperature of 30 degrees C with the yield of 62% for (R)-MA and the enantiomeric excess (e.e.) of 98% for (R)-MA. The immobilized cells showed good operation and storage stability. (C) 2007 Elsevier Ltd. All rights reserved.