the resolution of racemic phenylalanine esters with esterases has been reexamined in relation to the development of a continuous process based on the use of hollow fiber supported liquid membrane (slm) reactors. the requirement for high enantioselectivity was met by phenylalanine isopropyl ester, whose (r)-enantiomer was found refractory to the action of subtilisin carlsberg in water, ph 7.5, at 25 $degree$ c. the continuous feeding of (r,s)-phe-o-ipr $center dot$ hcl at 2 mm/h to 0.7 g/l subtilisin resulted in steady-state reaction conditions that gave (s)-phe-oh of 95 enantiomeric excess (ee) at the theoretical rate. the unreacted (r)-phe-o-ipr, which permeated out continuously, had 80 ee and was racemized quantitatively by heating with a salicylaldehyde catalyst in refluxing toluene doubling the feeding rate (4 mm/h) created excessive accumulation of (r)-phe-o-ipr in the reactor, which inhibited the enzyme through nonproductive binding, lowering the (s)-phe-oh resolution rate to 68 of the theoretical rate. similar experiments with (r,s)-phe-ome $center dot$ hcl gave (s)-phe-oh of 9-48 ee, due to the enzymatic hydrolysis of (r)-phe-ome experienced during the runs. when $alpha$ -chymotrypsin was used for the continuous hydrolysis of (r,s) -phe-o-ipr, the isolated (s)-phe-oh showed 67 ee, indicating that substantial hydrolysis of the (r)-ester had occurred. (author abstract) 17 refs