Research On Hydrogen Production By Clostridium Hydrogeniproducens T2 Using Pentose And Hexose

The technology of anaerobic ferment to produce hydrogen can be widely applied in the future, however, there are still some problems, such as how to improve the systematic efficiency and operational stability and how to lower the product costs ,which need resoving. Many articles have been published on obtaining the substrates producing hydrogen in high-efficiency and low-cost. Lignocellulosic material can be found easily and is of large reserves and low prices. But it is less efficient if the material has been directly applied to produce hydrogen. By means of physical, chemical, or biological methods to pretreat, the material is translated into hexose and pentose for fermentation,which result in a substantial increase in hydrogen production. In this dissertation, experiments were carried out on the hydrogen production with hexose and pentose by strain T2,which are benefit to utilize cellulose to reduce the hydrogen-production cost both theoretically and practically.The efficiency of hydrogen production is directly related to the quality of the bacteria. Clostridium hydrogeniproducens T2 is a new species under Clostridium and a typical Mesophilic bacteria. This paper using it for fermentative hydrogen production, it was conducted in batch mode and used glucose as substrate to analyze the effect of substrate concentration and inoculum size on the hydrogen production capacity on it. By different methods of cultivation, we analyze the ways of strain T2 using glucose and xylose and the rules of its growth and hydrogen production. Finally there was a study on the capacity of strain T2 when utilizing the hydrolyzate pretreatment solution of corn cob.Based on the obtained optimal substrate concentration and inoculums which is 60 mmol/L and 10%, investigated the hydrogen production characteristics of pure glucose, mixed sugar (glucose and xylose ratio 3:1,1:1,1:3), pure xylose as the substrate respectively. The results showed that strain T2 can synchronously utilize glucose and xylose, However, when the substrate are mixed carbohydrate in the ratio of 3:1 and 1:1, glucose showed obvious inhibition of strain T2 using xylose, xylose utilization rate is merely about 30%.As fed-batch cultivation can release the glucose inhibition of yeast fermentation, a further study was maded on hydrogen production of T2 under the conditions of fed batch cultivation. The results showed that in fed-batch culture conditions, total sugar utilization rate was 79.5%, compared with the batch culture increased 27.7%. On this basis, further experiments on continuous culture of strain T2 with pure glucose, mixed sugar (glucose and xylose ratio 3:1,1:3), pure xylose respectively, showed that T2 can also synchronously utilize glucose and xylose and compared with the batch culture, however, achieved higher hydrogen production and hydrogen production rate, the hydrogen production rate were 2.79 mol-H₂/mol- glucose,2.7 mol-H₂/mol-mixed sugar ,2.09 mol-H₂/mol-mixed sugar,1.79 mol-H₂/mol-xylose.Hydrogen production by corncob were studied. After determined the composition of corn cob, three kinds of pretreatment was acted on it which are acid gas explosion, gas explosion and alkali treatment. The pretreatment solution were then utilized as the substrate of hydrogen production. The results show that, strain T2 has the strong capacity of hydrogen production using hydrolyzate pretreatment solution of corncob. The saccharification rate by pretreatment with acid gas explosion was about 72%, the hydrogen production rate was 124 ml-H₂/g-corncob and 173.6ml-H₂/g-reducing sugar. The saccharification rate by pretreatment with alkali was about 67%, however, the lag phase of strain T2 was up to 11h, which in the result of slow hydrogen production rate. After the pretreatment of gas explosion, saccharification rate is relatively low at 59%, on the other hand the hydrogen production is higher: 159.3ml-H₂/g-reducing sugar. By adopting this approach, the pretretment costs are low ,which showed gas explosion also a good way of pretreatment corncob.