Microbial optical resolution was investigated for the practical production Of D-homoserine from DL-homoserine. A bacterial strain, 2-3, that enantioselectively degrades the L-enantiomer from DL-homoserine was isolated and identified as Arthrobacter nicotinovorans. Strain 2-3 grew on medium containing 5% (W/V) DL-homoserine hydrobromide (275 mM) as the sole carbon and nitrogen source and enantioselectively exhausted the L-enantiomer in 48 h. The D-enantiomer was recovered from the culture broth with an enantiomeric excess of >99.9%. In addition, washed cells of the strain 2-3 were able to perform complete optical resolution at an initial DL-homoserine hydrobromide concentration of up to 5 10 mM, with a velocity of 0.28 mmol (g cell dry weight)(-1) h(-1). (c) 2007 Elsevier Inc. All rights reserved.