Anaerobic Acid Production Characteristics And Microbial Diversity Analysis Of Livestock Manure

Volatile fatty acids(VFAs)are the important intermediate metabolites during the anaerobic digestion(AD)of organic matter,which not only can be further conversed into methane,but also can be used as raw materials to synthesize high value-added bio-based materials.However,the information on anaerobic acidification of animal manure is limited.On the basis of the status,the mesophilic batch anaerobic acification tests were carried out to explore the acidification metabolism of pig manure,chicken manure,and cow manure under different initial pH levels.In addition,the microbial communities were analyzed,and the relationship between the dominant microflora and the VFAs production was also investigated.This study aims to provide theoretical support for the high value utilization of animal manure by AD process.The results showed that the initial pH value significantly affected the VFAs production and the type of acidification metabolism of pig manure,chicken manure,and cow manure.The maxium TVFAs production was obtanied at initial pH values of 10.0,10.0,and 9.0 for pig manure,chicken manure,and cow manure,respectively,which was 648.1(14 d),646.2(17 d),and 413.5(14 d)mgCOD/gVS,respectively.In addition,the acidification metabolic types of pig manure,chicken manure,and cow manure were butyric acid fermentation,propionic acid fermentation,and mixed acid fermentation,respectively.The results of 16S rRNA gene sequencing showed that microbial community diversity in these three animal manure acidification system was significantly different under different initial pH conditions.Under the optimal conditions of acidfication,the dominant acid-producing bacteria in the acidification system of pig manure is Clostridiaceae,which can degrate polysaccharides to be acetate and butyrate.In the chicken manure acidification system,the abundance of Caldicoprobacterhe,one Polysaccharide hydrolytic bacteria and Proteiniphilum,one protein degradation bacteria was 38.2%and 31.1%,respectively.Different from pig manure and chicken manure,in the cow manure acifacation system,the abundance of salt-tolerant Porphyromonadaceae was relative higher.Moreover,the Rutinococaceae and Clostridiaceae are also the dominant microflora,which can efficiently degrade lignocellulose.