Study On The Correlation Between Abundance Of Functional Genes In Nitrogen Cycle And Physic-chemical Parameters During Pig Carcass Composting

Safe and effective treatment of pig carcasses is a common problem faced by Chinese farms.Composting is widely used throughout the world as a method for the harmless treatment of livestock and poultry carcasses.However,there are problems such as low efficiency and severe nitrogen loss during pig composting.In order to investigate the physicochemical parameters of the compost in pig carcasses and the changing rules of the genes involved in nitrogen cycle microbial functions,this study carried out aerobic static composting of pig carcasses,measured the physicochemical parameters during the composting process.Fluorescence quantitative PCR was used to detect the abundance changes of the functional marker genes involved in nitrogen cycle in compost,and the effects of physicochemical parameters on functional genes were analyzed.The results of the study are as follows:1.An aerobic static composting experiment was conducted on the pig carcasses and it was found that the experimental group(added microbial inoculum)and control group both rose to 50? on the second day and reached a maximum temperature of68.3? on the fourth day.the temperature of the experimental group and the control group was higher than 50? was 34 days and 26 days,respectively.The change of pH value in the pile of compost showed an overall trend that increasing first and then decreasing.The pH value ranged from 7.75 to 8.71,and the difference was not significant.Combined with other physicochemical parameters,it was known that the compost was fully decomposed,and the compost was harmless.2.Using quantitative real-time PCR detection,it was found that 16 S rDNA,amoA,narG,nirK,nosZ and nifH genes can be detected in the composting process.The four gene abundances of narG,nirK,nosZ,and nifH were higher during the period from the composting warming period to the mid-high temperature period,and the gene abundance was lower in the later stage of high-temperature composting and maturing.The amoA gene in the experimental group decreased in the late period of high temperature period,and rose to the level equivalent to the warming period in the maturity period.Compared to the level of 16 S rDNA in the compost,amoA<narG,nirK,nosZ<nifH.3.Using SPSS software for correlation analysis,it was found that the abundance of amoA gene involved in nitrification decreased as the water content decreased.Theabundance of narG gene involved in denitrification will decrease with the decrease of water content.The abundance of nirK and nosZ genes will decrease along with the decrease of water content,but also decrease with the increase of ammonium nitrogen content.The abundance of nifH genes involved in nitrogen fixation decreased with decreasing water content,also decreased with increasing ammonium nitrogen content.