Semi-solid state fermentation of bagasse for hydrogen production; the cost-effective approach in Indian context

Semi-solid state fermentation route of hydrogen production from agrowaste sugarcane bagasse was tried using the photosynthetic bacterium Rhodopseudomonas (BHU strain-1) and the non-photosynthetic Enterobacter aerogenes MTCC2822. The process seems an alternative to submerged fermentation that requires high volumes of nutrient broth. Bagasse (10 g) pre-hydrolyzed with NaOH (2%, w/v) was coated with Ca-alginate (1.5%, v/v) containing Rhodopseudomonas and E. aerogenes in the co-immobilized state (300 μg bacterial biomass ml). The fermenting medium was just 150 ml to sustain the moistened bagasse in a 0.5 L fermenter kept in light. A parallel set of free bacterial cells served as control. Hydrogen production by the immobilized sets reached 30 L within 60 h with the average rate of 0.177 L H2 h. For free cells, the values for hydrogen output (20 L) or the rate 0.1125 L H2 h were approximately 1.5-fold low. It is proposed that semi-solid fermentation route of hydrogen production from bagasse will be a cost-effective technology in countries generating this agrowaste.