Research On The Construction And Regulatory Techniques Of Bionic Rumen Anaerobic Fermentation System

Renewable bio-energy obtained from the anaerobic fermentation of orgnic complex matters has a great significance to protect the environment and mitigating energy shortage.However,the low conversion efficiency of conventional anaerobic fermentation system for the refractory cellulosic biomass limits its large-scale application.The cellulosic biomass can be effectively degraded in the rumen of ruminants.From the perspective of bionics,different bionic rumen anaerobic fermentation systems are constructed to produce acids and CH₄,respectively,and then the key technologies of the bionic rumen anaerobic fermentation system using the rumen microorganisms are researched in this study.The main results and conclusions are made as follows:(1)The lignocellulose degradation characteristics of rumen microorganisms and the cosubstrate strategy with lignocellulosic biomass and food waste(FW)for enhancing lignocellulose degradation during rumen fermentation were studied.The characteristics of rumen microbial community and the dominant lignocellulolytic functional rumen microbes were revealed by Illumina Mi Seq sequencing technology.The functional rumen microbiome is mainly composed by ruminal bacteria,fungi,and archaea.Ruminal bacteria and fungi are mainly involved in lignocellulose degradation.Clostridiales order including Lachnospiraceae NK3A20 group,Caproiciproducens,unclassified Clostridiaceae 1 and unclassified Family XI genera and the genus Wallemia were the predominant lignocellulolytic ruminal bacteria and fungi,respectively.The rich lignocellulolytic enzymes were secreted by the abundant and diverse rumen bacteria and fungi contributed to the persistent hydrolysis of lignocellulosic wastes.And the corresponding high VFA yield of 0.484 g COD/g VS was achieved.The diversity and richness of functional rumen microbes in rumen fermentation were promoted with FW as a cosubstrate,and the cosubstrate strategy with lignocellulosic biomass and FW can be used to enhance lignocellulose degradation during rumen fermentation.(2)Through simulating the rumen physicochemical environment of ruminant herbivores and inoculating rumen fluid,the batch and semi-continuous bionic rumen anaerobic fermentation systems were constructed in anaerobic batch reactor and dynamic membrane bioreactor,respectively,and then compared the cosubstrate degradation characteristics of large ruminant cow rumen microorganisms and small ruminant sheep rumen microorganisms.The hydrolysis and acidification efficiency of hemicellulose and lignin of cow rumen microorganisms was higher than that of sheep rumen microorganisms.Moreover,the cellulose degradation capability of sheep rumen microorganisms was higher than that of cow rumen microorganisms.Thus,the cow rumen microorganisms were more suitable than sheep rumen microorganisms for lignocellulosic biomass degradation and maximized the hydrolysis conversion through the anaerobic fermentation.The high interception ability of the dynamic membrane layer formed in the semi-continuous bionic rumen anaerobic fermentation system reduced the washing out of rumen microorganisms and then improved the degradation degree of lignocellulose biomass.The cow rumen microorganisms could secrete more lignocellulolytic enzymes to hydrolyze lignocellulosic biomass than the sheep rumen microorganisms.During the construction and operation process of the batch and semi-continuous bionic systems,the diversity and richness of functional rumen microbes can be well maintained in the bionic rumen anaerobic fermentation system by inoculated the cow rumen microorganisms.(3)Due to the limitations of rumen fluid in the industrial applications,a stable and high-rate bionic rumen anaerobic fermentation system for CH₄was constructed and realized with cow manure(CM)as the source of rumen microorganisms instead of rumen fluid through long-term acclimatization in a conventional single-stage mesophilic anaerobic fermentation system.The maximum CH₄production of 2.71 CH₄L/L/d was achieved.The cellulose,hemicellulose,and lignin were effectively degraded by 78.3%,58.8%,and 47.5%,respectively.With CM addition,more rumen functional microbes(Syntrophomonas,Candidatus Cloacamonas,Clostridium III,Sedimentibacter and Mucor circinelloides genera)were identified from the bionic rumen anaerobic fermentation system for CH₄,and then further enhanced the degradation of cosubstrate.During the construction process,continued increase of enzyme activity was improved in terms of the anaerobic fermentation enzyme and lignocellulose-degrading enzymes.The microbes,including those brought into the bionic rumen anaerobic fermentation system from CM,tended stable after adapt to the changed environment.Without continued CM addition,a stable operation still can be maintained at the high-rate conditions,and the maximum CH₄production was as high as 5.86 CH₄L/L/d.In addition,the bionic rumen anaerobic fermentation system for CH₄was not apparently hindered,and the functional rumen microbes still can be enriched without CM addition.During the construction process of the bionic rumen anaerobic fermentation system for acids,the use of cow rumen microorganisms and dynamic membrane bioreactor is a promising way for industrial engineering to biodegrade cosubstrate for acids production.On the other hand,using CM as the source of cow rumen microorganisms instead of cow rumen fluid,a stable and high-rate bionic rumen anaerobic fermentation system for cosubstrate degradation for CH₄production was constructed in the dynamic membrane bioreactor with CM as inoculum,which provides a proctical technical approach for realizing high-rate anaerobic fermentation system for energy.