Abstract:

In this work, the effects of total concentration of glucose-xylose mixture and mass ratio of xylose to glucose on hydrogen production, hydrogen production efficiency, bacteria growth and residual sugar content were investigated in the co-fermentation of glucose and xylose.It was shown that maximum hydrogen production efficiency of 2.1—2.2 mol H₂·mol^-1 was obtained from xylose at initial xylose concentration of 5—10 g·L^-1, which was twice of that from glucose under the same experimental conditions.And the maximum cumulative hydrogen yield of 3020 ml·L^-1 was obtained at initial xylose concentration of 15 g·L^-1，which was equal to that from glucose at initial glucose concentration of 30 g·L^-1.As initial sugar concentration was greater than 30 g·L^-1, cumulative hydrogen yield from xylose was found to decrease rapidly, while a slow increase was found from glucose with increasing sugar concentration.Under a mixed sugar environment with initial total sugar concentration of 15 g·L^-1, maximum cumulative hydrogen yield was obtained at the mass ratio of 1∶0.5(xylose to glucose), which was the best environment for bacteria growth.However, at initial total sugar concentration of 30 g·L^-1, the medium with a mass ratio of 1∶2(xylose to glucose)was the best environment for bacteria growth.In this case, an optimum cumulative hydrogen yield of 4150 ml·L^-1 was obtained, which was 1.37 or 1.46 times of that from respective fermentation of glucose or xylose at initial concentration of 30 g·L^-1. In the co-fermentation process of glucose and xylose, both of glucose and xylose were consumed simultaneously in different degrees by anaerobic mixed microflora.It was interesting to note that xylose was easier consumed than glucose at the concentration less than 15 g·L^-1, while glucose was easier consumed than xylose at the concentration greater than 22.5 g·L^-1.The results would be helpful for the further study of hydrogen production from biomass.