Mixed microbial cultures (MMCs) based on 11 isolates belonging to Bacillus spp. (Firmicutes), Bordetella avium, Enterobacter aerogenes and Proteus mirabilis (Proteobacteria) were employed to produce hydrogen (H-2) under dark fermentative conditions. Under daily fed culture conditions (hydraulic retention time of 2 days), MMC6 and MMC4, immobilized on ligno-cellulosic wastes banana leaves and coconut coir evolved 300-330 mL H-2/day. Here, H-2 constituted 58-62% of the total biogas evolved. It amounted to a H-2 yield of 1.54-1.65 mol/mol glucose utilized over a period of 60 days of fermentation. The involvement of various Bacillus spp. - Bacillus sp., Bacillus cereus, Bacillus megaterium, Bacillus pumilus and Bacillus thuringiensis as components of the defined MMCs for H-2 production has been reported here for the first time. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.