Bench-scale fermentation for second generation ethanol and hydrogen production by Clostridium thermocellum DSMZ 1313 from sugarcane bagasse

Abstract

Exploration of eco-friendly energy resources substituting conventional fossil fuels is the real challenge globally. Prospectively, current investigation accentuates the fermentative conversion of low-cost lignocellulosic biomass waste, sugarcane bagasse (SCB) into bioethanol and biohydrogen exploiting thermophilic cellulolytic bacterium Clostridium thermocellum DSMZ 1313. Initially, the optimization of some key fermentation factors for bioethanol and biohydrogen productions was done in 150 ml serum bottles employing Taguchi orthogonal array L27 (3̂13) experimental design. Results elucidated that the most suitable factors for ethanologenesis were 70 g/L cellulose, 10 g/L corn-steep liquor (CSL), 15 mg/L ferrous sulfate (FeSO4·6H2O), 1 g/L magnesium chloride (MgCl2·6H2O), pH 7, and 5 days incubation whereas for hydrogen fermentation were 60 g/L cellulose, 30 g/L CSL, 5 mg/L FeSO4·6H2O, 2 g/L MgCl2·6H2O, pH 7, and 3 days incubation. Quantitatively, 7.422 g/L ethanol and 56.891/50 ml hydrogen were produced from cellulose while 6.352 g/L ethanol and 51.685/50 ml hydrogen with H2SO4-pretreated SCB (substituted with cellulose). Scaled-up suspended-cell fermentations in bench-scale stirred-tank bioreactor resulted in 11.77% increased ethanol yield (0.239 g ethanol/g of glucose) and twofold higher hydrogen volumes (106.88 ml hydrogen/g of glucose). The employment of SCB directly as substrate for biofuels production has appeared sustainable to meet the high global energy demands.