We have developed a compact stacked flatbed reactor (CSFR) composed of several pieces of agar plates containing an H(2)-producing bacterium, Escherichia coli. The bacterium was immobilized at high density (8 mg dry cell/ml agar) in the flatbed agar plate with 1.5-2 mm in thickness, producing H(2) under fermentative conditions. These flatbeds were vertically assembled to enable the easy extraction of products from the reactor. In batch reaction at 100 mM glucose as a starting substrate, more than 90% of glucose was consumed, resulting in the maximum H(2)-production rate of 6.7 l H(2)/g dry cell/l reactor/h and total H2 yield of 1.2 mol H(2)/mol glucose. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.