Effects of oxygen transfer (OT) on benzaldehyde lyase (BAL) production by recombinant E. coli BL21 (DE3) pLySs were investigated at an air-inlet rate of Q(O)/V(R) = 0.5 vvm and agitation rates of N = 250, 500, 625, and 750/min; and at constant dissolved oxygen (DO) concentrations of C(DO) = 0.04 and 0.08 mol/m(3), on a glucose based defined medium. The highest cell concentration (C(X) = 3.0 kg/m(3)) and volumetric BAL activity (A = 1095 U/cm(3)) were obtained at C(DO) = 0.08 mol/m(3). K(L)a increased with agitation rate and decreased with C(X). The highest K(L)a (= 0.039 s((-1)) was obtained at Q(O)/V(R) = 0.5 vvm and N = 750/min. Damköhler number increased with decrease in agitation rate and increase in C(X), while the effectiveness factor was inversely proportional to C(X). The specific growth rate and the yield coefficients decreased with cultivation time and higher values were obtained in higher agitation rates. Oxygen consumption and glucose consumption for maintenance were changed proportionally and inverse proportionally with the BAL production, respectively.