The present study investigated hydrogen production potential of novel marine Clostridium amygdalinum strain C9 isolated from oil water mixtures. Batch fermentations were carried out to determine the optimal conditions for the maximum hydrogen production on xylan, xylose, arabinose and starch. Maximum hydrogen production was pH and substrate dependant. The strain C9 favored optimum pH 7.5 (40 mmol H(2)/g xylan) from xylan, pH 7.5-8.5 from xylose (2.2-2.5 mol H(2)/mol xylose), pH 8.5 from arabinose (1.78 mol H2/mol arabinose) and pH 7.5 from starch (390 ml H(2)/g starch). But the strain C9 exhibited mixed type fermentation was exhibited during xylose fermentation. NaCl is required for the growth and hydrogen production. Distribution of volatile fatty acids was initial pH dependant and substrate dependant. Optimum NaCl requirement for maximum hydrogen production is substrate dependant (10 g NaCl/L for xylose and arabinose, and 7.5 g NaCl/L for xylan and starch). (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.