Optimization of key factors affecting biohydrogen production from microcrystalline cellulose by the co-culture of Clostridium acetobutylicum X9 + Ethanoigenens harbinense B2

Abstract

The key factors (initial pH value, substrate concentration, incubation time, C/N and L-cysteine concentration) that affect biohydrogen production from microcrystalline cellulose in batch fermentation by the co-culture of isolated strains (Clostridium acetobutylicum X₉ + Ethanoigenens harbinense B₂) were optimized using an orthogonal experiment. The isolated strain, Clostridium acetobutylicum X₉, had high hydrogen yield from microcrystalline cellulose (MCC), and Ethanoigenens harbinense B₂ could produce hydrogen efficiently from monosaccharides directly from microcrystalline cellulose. The optimal parameters were as follows: initial pH value of 6.0, 12 g L⁻¹ substrate concentration, 40 h incubation time, 0.7 g L⁻¹ L-cysteine concentration and a 4 : 1 ratio of C/N. Under the optimum culture conditions, a maximum hydrogen yield rate of 10.4 mmol g-MCC⁻¹ was obtained. This yield is approximately 2.2-fold greater than that of mono-culture Clostridium acetobutylicum X₉. It suggests that the optimal conditions achieved can be applied to the production of hydrogen from microcrystalline cellulose using the co-culture of isolated strains, Clostridium acetobutylicum X₉ + Ethanoigenens harbinense B₂.