|Other Abstract||With the increasing of resources shortage, energy crisis and environmental pollution, much attention has been focusing on anaerobic digestion (owing to its high pollution removal ability and renewable energy generation: hydrogen or biogas). Microbes are the main vehicle for anaerobic digestion, which determine the production efficiency. Therefore, it is significant to pay attention to exploitations of highly more efficient microorganisms and optimize the fermentation conditions, which is responsible for the efficiency of anaerobic technology. Previously, we isolated a hydrogen producing ethanol-type bacterium Hydrogenispora ethanolica LX-B. In this study, the characteristic about anaerobic biohydrogen of this bacterium, application the bioaugmentation technology into the anaerobic digestion of corn straw was investigated. Results showed that the strain possess high hydrogen production efficiency, application into the anaerobic digestion of corn straw could accelerate the degradation of straw and improve production efficiency in the condition of energy saving, environmental friendly and mild conditions. Main contents and results of the present study are as follows:
1. The biohydrogen production potential of Hydrogenispora ethanolica LX-B was studied. Firstly, the effect of glucose and products inhibition by acetate, ethanol and hydrogen on the growth and hydrogen production was assayed. Results showed that Hydrogenispora ethanolica is a promising strain for hydrogen production with relatively high hydrogen yields, high growth rate, a wide rage of substrate utilization and production tolerance. The bacterium grew well and kept high hydrogen yield in a wide range of initial glucose concentrations up to 41.5 g/L. The maximal yields of 1.8 mol H2/mol glucose and 1.4 mol ethanol/mol glucose were observed at 1.1 g/L glucose at 37 °C and pH 7.0. Neither acetate nor ethanol exhibited significant inhibition: the addition of ethanol or acetate up to 100 mM only had less than 20% inhibition on the growth and glucose consumption during two weeks of incubation. Besides, under high hydrogen partial pressure of 27 mmol/L culture, the growth and glucose consumption of the pure culture was not inhibited. Secondly, hydrogen production ability on various sugars and corn straw was also investigated. Results demonstrated that the strain could grow on pentose, hexose and polyose, in which glucose, xylose, arabinose, mannose and galactose are the preferred carbon source. Besides, the strain would be an ideal candidate for hydrogen production with cellulosic biomass. The maximum H2 yield of 6.8 mL/g was achieved by NaOH-pretreated corn straw, which was 21.9% higher than the control (5.6 mL/g-corn straw).
2. The bioaugmentation effect of H. ethanolica LX-B on anaerobic digestion of corn straw was studied. Results showed that bioaugmentation with the strain could increase 16-18% methane yield of corn straw degradation. The maximum methane yield was 233.8 mL/g-corn straw with 5% inoculation. H. ethanolica could improve the methane yields from methyl cellulose and xylan (models for cellulose and hemicelluloses, respectively) by 21.7% and 14.2%. A proposed mechanism is that H. ethanolica promotes more hydrolysates of lignocellulosic biomass (such as pentose and hexose) to ethanol, acetate and hydrogen, and provides a source of substrates for the methanogens. As a result, the degradation of cellulose of corn straw were improved.|