Thermophilic combined bioproduction of ethanol and hydrogen utilizing sugarcane bagasse

Abstract

Research addressing investigation of environment-friendly and efficient fuel reservoirs substituting depleting fossil fuels is at-work worldwide. For this purpose, it is of ultimate requirement to establish cost-effective biofuel fermentative processes using renewable lignocellulosic bio-wastes as feedstock. The present investigation compacts the employment of Clostridium thermocellum DSMZ1313, for bench-scale co-production of bioethanol and biohydrogen (bioH2) under non-aseptic thermophilic conditions. In our previous study, the fermentation kinetics have been studied aseptically in bench-scale stirred-tank bioreactor with same fermentative bacterium under optimized levels of the key fermentation factors employing sugarcane bagasse (SCB) in the fermentation medium. In the current investigation, for co-production of bioethanol and bioH2, batch fermentation was carried as free cell approach in subsequent bioreactor’s modifications that resulted in enhanced biofuels’ yields aseptically. These include the incorporation of immobilized cells fibrous bed bioreactor (FBB) that caused 20.465% enhanced ethanol and 27.27% higher level of hydrogen, followed by substrate addition (fed-batch fermentation) resulted in 61.79% increased ethanol and 74.074% better hydrogen production. Selective stripping of the inhibitory metabolites by in-situ gas-stripping was also performed that resulted in 94.58% increased ethanol and 105.38% elevated hydrogen level. Finally, under non-aseptic thermophilic fermentation conditions, 16.07% reduced ethanol whereas 14.7% elevated hydrogen levels were obtained in comparison with aseptic fermentation conditions. The simultaneous formation of bioethanol and bioH2 by SCB usage as biofuels’ feedstock from C. thermocellum-DSMZ1313 under non-aseptic settings has appeared a potentially sustainable recourse to produce environmentally friendly energy sources. To overcome the non-sterile fermentation processes’ inefficiencies, further studies might prove useful for active large scale deployment of waste biomass-to-biofuel.