Here we present a simple bioreactor with immobilized rat hepatic microsomal membranes which may be applicable in screening and prediction of reactive intermediates (RI) using alumina membrane as a support. To monitor the effectiveness of our technique, acetaminophen (AP) already known to produce RI has been utilized as a model compound. The resulting immobilized enzyme membrane (IEM) was able to produce reasonable amount of glutathione conjugates within a residence time of seconds. At the other end biosensor was tailored to predict RI by relating the enhanced activities of microsomal glutathione S-transferase (mGST) as a marker of drug and chemical stress. (C) 2009 Elsevier Inc. All rights reserved.