A mathematical model describing the kinetic resolution of alpha-methylbenzylamine (alpha-MBA) in a two-liquid-phase system (water/ cyclohexanone) is presented by using omega-transaminase from Bacillus thuringiensis JS64. The model takes into accounts the kinetics of omega-transaminase and the mass transfer of alpha-MBA and acetophenone between the two phases. The model in the phase separation state at low agitation speeds is extended to that in an emulsion state at high agitation speeds by factoring in faster enzyme inactivation and higher mass transfer rate owing to the increased interfacial area. Model predictions were reasonably consistent with the experimental results in both 2- and 100-ml batch reactors. Various simulation results by using the model indicate that: (1) pH in the aqueous phase should be maintained at 7 because a high aqueous concentration of alpha-MBA is attained and the optimal pH for enzyme activity appears to be around 7; (2) maximum agitation during the phase separation state is the optimal mixing condition given the two counteracting factors, i.e, mass transfer limitation and interfacial enzyme inactivation; and 3) the optimal volume ratio (V-aq:V-or) is 4:1.