In this work, multiple reuses of Rhodococcus ruber TH3 free cells for the hydration of acrylonitrile to produce acrylamide in a membrane dispersion microreactor were carried out. Through using a centrifuge, the reactions reached 39.9, 39.5, 38.6 and 38.0 wt% of the final acrylamide product concentration respectively within 35 min in a four cycle reuse of free cells. In contrast, using a stirring tank, free cells could only be used once with the same addition speed of acrylonitrile with a microreactor. Through observing the dissolution behavior of acrylonitrile microdroplets in a free cell solution using a coaxial microfluidic device and microscope, it was found that the acrylonitrile microdroplets with a diameter of 75 mu m were rarely observed within a length of 2 cm channel within 10 s, which illustrated that the microreactor can intensify the reaction rate to reduce the inhibition of acrylonitrile and acrylamide. (C) 2015 Elsevier Ltd. All rights reserved.