| With merits of high energy density（122 MJ/kg）,clean,and ability to be sufficiently conversed through fuel cell or internal combustion engine,hydrogen was suggested as one of the promising types of energy in future.Photobiological hydrogen production was considered as a sustainable approach since it can be coupled with the sufficient degradation of organic wastes using solar energy,and operated under mild conditions.Lignocellulosic biomass were rich in hydrocarbonates,which were suitable to meet needs of microbial and the resources are huge and renewable.However,lignocellulosic have structurally difficult-to-degradability and compositional complexity,how to efficiently hydrolyze them and enhance the hydrogen production and metabolism capacity of photosynthetic bacteria based on lignocellulose is important for the efficient development of waste lignocellulose resources significance.Aiming to enhance the lignocellulose-H2 production through photobiological way,research works were in sequence carried out.Firstly,an alevornal photobioreactor with photosynthetic bacterial biofilm was constructed to investigate strategies for the improvement of stable productivity in hydrogen by the immobilized cells of photosynthetic bacteria（PSB）using glucose as the sole carbon source.Then,enhancement of the metabolism in cell growth and hydrogen evolution of PSB was conducted in a suspended cultured bioreactor using the mixed carbon substrate of glucose and xylose.Thirdly,enhancement of photobiological hydrogen production from hydrolysate of straw was employed.A photobioreactor with high specific area by regular cutting grooves on the surface of transparent PMMA material.Experiments with Box-Behnken design was employed to optimize key operational parameters for achieving the maximal hydrogen production performance of bioreactor,and resulting in the maximal hydrogen production rate（HPR）at 57.6±0.3 mL/h/L with a H2 yield of 1.8 mol H2/mol glucose under conditions of 125.9μE/m2/s light intensity with 590 nm light wavelength,52.4 mM initial glucose concentration and flow rate of 209 mL/h.Characteristics of grooves in strengthening the convective mass transfer and distributing evenly in incident light was considered to positive affecting ability of stable photosynthetic bacterial biofilm for their nitrogenase activity in H2 production by the sufficiently providing of reducing power and ATP.Glucose and xylose were the two main reducing sugars in hydrolysate obtained after pretreatment of raw lignocellulosic materials（RLM）.To efficient fermentation of organic carbon within RLM,experimental studies were carried out to optimize the process of such a mixture carbon based photofermentation using RSM technique.The results indicated that when the initial substrate concentration,the content of glucose in the carbon source and the light intensity were 39 mM,59%mol/mol and 12.6 W/m2,the maximum hydrogen production rate was 28.57±0.6 mL/h/L.The hydrogen yield is 1.26mol H2/mol mixed sugar,and the light energy conversion efficiency is 12%.More nutrients and stable microenvironment provided by such a mixed sugar can realize a faster growth of cells and enhance H2 production activity of nitrogenase,therefore resulted in the improvement of H2productivity of bioreactor.The optimized hydrolyse with under conditions of the the temperature is 200℃,time50 min,solid-liquid ratio 1:15,dilute hydrochloric acid concentration 0.6%,ultrasonic power 200W,time at 20 min.At this time,the reducing sugar yield was 40.2%,the glucose concentration was 72 mM,and the xylose concentration was 92 mM.this obtained by the combined pretreatment through grinding,dilute acid,liquid hot water and microwave.Studies on enhancing H2 productivity from RLM were revealed that based biohydrogen was enhanced to get a higher rate of H2 production in 25.6±0.6 mL/h/L,H2 production potential of 1119±20 mL/L and H2 yield of 1.18mol H2/mol lignocellulosic hydrolysate were attained under the H2 production conditions of the initial substrate concentration 42 mM,the initial substrate concentration and the initial inoculum ratio 0.38 mmol/mg（initial inoculation cell concentration is 0.11 g/L）and the light intensity is 14.96 W/m2（wavelengthλ=590 nm）.As an abundant resource rich in carbohydrates,lignocellulosic materials has a wide perspective in their utilization.Investigations in this work can provide necessary references including configuration,operation and regulation of bioreactor for the future exploration on techniques of high efficient transform of lignocellulose into H2,and thus give aidances for both therotical and practial studies in the future. |
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