Organic matter in sewage sludge can be converted into volatile fatty acids (VFAs) as renewable carbon sources. This work for the first time demonstrates that beta-cyclodextrin (beta-CD) molecules enhance sludge hydrolysis for production of VFAs. With 0.2 g beta-CD g(-1) dried solids (DSs), the increment rate for VFAs peaked at 4200 g g(-1) DSs g(-1) beta-CD, with acetate and propionate as the predominant VFAs. Compositional and microbial community analyses confirm that the beta-CD molecules break a cell's membrane, such that it releases intracellular substances. Although beta-CD molecules inhibited activities of methanogens, they did not impair those of acid-forming bacteria, thereby demonstrating that beta-CD-assisted VFAs are renewable organic carbon sources, except in anaerobic digestion processes. (C) 2011 Elsevier Ltd. All rights reserved.