Regulation Of Iron-loaded Biochar On Hydrogen Production With Xylose As Substrate By Thermoanaerobacterium Thermosaccharolyticum W16

Hydrogen production by fermentation of straw-based biomassis a hot topic of current research,however,there are problems of low xylose utilization and low hydrogen yield during straw biomass fermentation for hydrogen production..Biocharcan enhance the efficiency of anaerobic fermentation due to its excellent physicochemical properties,but its enhancement effect is limited.Iron is widely used as an additive to promote hydrogen production because it is the metal component of the active centre of hydrogenase.Based on this,Thermoanaerobacterium thermosaccharolyticum W16,which can synchronise metabolism pentose and hexose to produce hydrogen,was used as the subject of this study.And then,prepared iron-loaded biochar from straw and Fe Cl₃ to investigate its effect on hydrogen production performance of the strain W16 and xylose consumption in the substrate.The correlation between the hydrogen production efficiency of thermophilic bacteria and the surface structural characteristics of iron-loaded biochar was investigated.The pyrolysis temperature and aoolication conditions of iron-loaded biochar were optimized.On this basis,we combined the dynamic changes of ORP,pH,Fe²⁺concentration and transcriptional level of essential genes of hydrogen production and metabolism to reveal the regulatory mechanism of iron-loaded biochar on xylose metabolism of thermophilic bacteria.The specific research results are as follows.The specific experimental results are as follows:The iron-loaded biochar was prepared by impregnation method at different pyrolysis temperatures.The results revealed that,with the increase of pyrolysis temperature,the content of the C element increased,the content of the Fe element decreased,and the specific surface area and total pore volume increased.At a pyrolysis temperature of 300℃,Fe₂O₃was successfully loaded;at 500℃,Fe₂O₃and Fe₃O₄crystalline forms were present,while at 800℃,iron was present in the form of Fe₂O₃,Fe₃O₄ and Fe⁰.ent in the form of and as well as.To address the problems of low conversion efficiency of xylose and low hydrogen production rate by W16,iron-loaded biochar prepared at different temperatures was added to the hydrogen production system with xylose as substrate,and the system with the same temperature pyrolyzed biochar additive was settled as control.The results showed that the higher the pyrolysis temperature of iron-loaded biochar exhibited a better promotion effect on hydrogen production.The maximum hydrogen production of 950.2 m L/L was obtained when iron-loaded biochar was added at 3.5 g/L with a pyrolysis temperature of 800℃,which was 81.8%higher than that of the control and 17.8%higher than the group with biochar additive.This indicates that the biochar modified with iron can further improved the hydrogen production efficiency of xylose fermentation by W16.And then,the effect of adding iron biochar with glucose and xylose mixed substrate on the hydrogen production efficiency of W16 was further investigated.It was found that the addition of iron-loaded biochar not only promoted the utilization of xylose in the sugar mix by W16,but also enhanced the consumption rate of glucose and xylose in mixed substrates.This result indicates that the addition of iron-loaded biochar effectively alleviated the carbon catabolite repression effect of W16 when mixed sugar was used as substrate.The mechanism of enhanced hydrogen production efficiency of W16 with xylose as substrate by iron-containing biochar was analyzed by combining the dynamic changes of ORP,pH,Fe²⁺concentration and transcript levels of key genes of hydrogen production metabolism.It was found that addition of iron-loaded biochar resulted in a smoother decreasing trend of pH,and a lower redox potential in the hydrogen production system.This indicates that iron-loaded biochar has an excellent buffering effect and creates a suitable environment for the growth of strain W16.It was found that Fe²⁺was gradually released from the fermentation hydrogen production system and the expression level of xylose isomerase gene increased after the addition of iron-carrying biochar by Fe²⁺concentration detection.It is possible that the Fe²⁺released from the iron-loaded biochar activated the metalloenzyme xylose isomerase,resulting in an increased level of the xylose isomerase gene expression,thus promoting the utilization of xylose by W16.