In this study, the kinetic characteristics of the bio-hydration of acrylonitrile by free cell catalysts were studied. Due to the aggregation phenomenon, free cell catalysts showed different characteristic when compared with free enzyme catalysts. The Michaelis constants were obtained through the homogeneous reaction. Both the values of Vm and Km increased with the increase in enzymatic activity, ranging from 100 to 500 U/mL, and the variation trend of Km was not consistent with the rule of enzyme-catalyzed reaction. To reduce the external diffusion resistance of acrylonitrile to free cells, a membrane dispersion micro reactor was used, and the conversion rates of acrylonitrile in the membrane dispersion micro-reactor under all of the experimental conditions reached approximately 90% of the max conversion rates. The reinforcement of the apparent reaction rate by the micro-reactor may have benefitted from the significant increase in the specific surface area of the acrylonitrile droplets and the adsorption of the free cell catalysts on the undissolved droplets. (C) 2017 Elsevier B.V. All rights reserved.