Optimizing the hydrogen (H(2)) yield at several initial pH conditions in a mixed batch anaerobic mesophilic culture fed with glucose and linoleic acid (LA) was performed using a three factor three level Box-Benkhen design (BBD). Based on the BBD approach, a statistical model was developed to predict the H(2) yield. The variables considered for the experimental design were the LA concentration, the initial pH and the number of times glucose was added to the culture. The D-optimality method predicted a maximum H(2) yield of 3.49 mol H(2) mol glucose(-1) for cultures fed 1.9 g l(-1) LA, maintained at an initial pH of 5.15 and received 1.79 glucose additions. The response outcome (H(2) yield of 3.38 +/- 0.22 mol mol glucose(-1)) at the nearest setting of the experimental factors (2.0 g l(-1) LA, an initial pH of 5.0 and two glucose additions) was 3.3% less than the predicted maximum value. The model provides a useful approach for predicting H(2) production when H(2) consumers are inhibited in mixed batch anaerobic cultures. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.