The effect of vitamin B(12) on hydrogen (H(2)) and 1,3-propanediol (1,3-PD) production in glycerol fermentation of Halanaerobium saccharolyticum subsp. saccharolyticum was studied in batch cultivations. In addition, the effect of vitamin B(12) on glucose fermentation of H. saccharolyticum subsp. saccharolyticum and on glycerol fermentation of H. saccharolyticum subsp. senegalensis, that is a non-1,3-PD producing bacterium, and of Clostridium butyricum, that is known for vitamin B(12)-independent 1,3-PD production, were studied for comparison. 1,3-PD production of H. saccharolyticum subsp. saccharolyticum was observed to be vitamin B(12)-dependent and the H(2) production in glycerol fermentation was remarkably enhanced when 1,3-PD production was blocked by the lack of vitamin B(12) supplementation. The highest H(2) yield obtained by H. saccharolyticum subsp. saccharolyticum was 2.16 mol/mol glycerol. No significant effects of vitamin B(12) on metabolite production in glucose fermentation of H. saccharolyticum subsp. saccharolyticum or in glycerol fermentation of H. saccharolyticum subsp. senegalensis or C. butyricum were observed. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.