Bioreactors were developed for water/oil heterogeneous enzymatic bioreactions. Using a cotton fiber disperser, small droplets (0.25 mm) of oil could be efficiently dispersed into an enzymatic water solution. 96 % conversion was achieved when olive oil was fed through the disperser from the bottom of the eight-staged bioreactor into the aqueous solution containing 500 U/mL Candida cylindracea lipase at 37°C.