Dark fermentative hydrogen production by defined mixed microbial cultures immobilized on ligno-cellulosic waste materials

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 (H2) 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 H2/day. Here, H2 constituted 58–62% of the total biogas evolved. It amounted to a H2 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 H2 production has been reported here for the first time.