Carbon Transformation And Related Microbial Community Succession In Dairy Manure-bagasse Pith Composting Regulated By Additives

A large amount of livestock manure and agricultural solid waste are produced every year in China,which causes serious environmental pollution.Aerobic composting,as an environment-friendly and economical technology,is widely used to treat organic solid wastes.During aerobic composting,microorganisms oxidize and decompose organic matter（OM）to form stable humic substances.In traditional aerobic composting,carbon is lost in the form of carbon dioxide,resulting in poor composting products.In order to solve the problem of carbon loss and improve composting quality,this dissertation aimed to explore the effects of different additives on physico-chemical parameters,carbon transformation,and the succession of related microbial community structure during dairy manure and bagasse pith composting by chemical,physical and biological methods.Organic carbon（SM:sugarance molasses）（T2）and inorganic carbon（NC:Na₂CO₃）（T1）were added to investigate the effects of different carbon source additives on the physico-chemical properties,dissolved organic matter（DOM）and the community structure and diversity of cbb L-containing autotrophic microbes（CCAM）in dairy manure and bagasse pith composting.The results showed that NC or SM could not only enrich the diversity of CCAM community,promote the degradation of organic matter（OM）,but improve the conversion of DOM to humic substances（HS）.From the analysis of ultraviolet spectrophotometer（UV-is）and Fourier transform infrared spectrometer（FT-IR）,SM or NC additive could promote the accumulation of aromatics and the degradation of unstable organic compounds to some extent.The results of flurscence quantitative PCR（q PCR）showed that NC additive was beneficial to the growth of CCAM community which were thermophilic microorganism.During the whole composting process,the abundance of cbb L gene increased first and then decreased.The highest value of copy number of control group（CK）,T1 and T2were 3.2933×10⁸,4.69×10⁸ and 3.2467×10⁸,respectively,and T1 was much higher than CK and T2 during the cooling period.In addition,the results of high-throughput sequencing indicated that Actinobacteria and Bacteroides were the dominant bacteria of CCAM in all treatments,while the abundance was significantly different.Peason cluster analysis revealed that Proteobacteria,Firmicuts,Acidobacteria and Nemadoda were positively correlated with the major environmental factors（C/N,OM and DOM）.To better reduce carbon loss and improve composting quality,the exploration of carbon cycle paths were expanded.Adenosine triphosphate（ATP）and nicotinamide adenine dinucleotide（NADH）（AN）were selected as additives that added at the initial stage of composting to explore its roles in carbon emissions,carbon transformation and related bacterial community succession.In order to further analysis the effects of NC additives on other additives and carbon emissions,ATP,NADH and NC（ANN）were added at the initial stage of another treatment.The results showed that ATP and NADH could improve carbon components degradation and transformation,and promote the succession of bacterial community,while the effects in ANN treatment were stronger,indicating that NC additive could enhance the synergistic effect of ATP and NADH.And ATP,NADH and NC could reduce CO₂ emission from different pathway.High-throughput sequencing showed that the dominant phyla were Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes,and the dominant genera were Pseudoxanthomonas,Kurthia,Bacillus and Corynebacterium＿1),while its abundance and diversity were significant different.Ternary analysis displayed that many unique bacterial communities were gathered in ANN,and Venn analysis showed that the number of total species and unique species in ANN were 753 and 42,respectively,which were much higher than those in CK（733 and 7）and AN（737 and 6）.In addition,CCA showed that OM,DOM and temperature（T）were the main environmental factors driving the succession of bacterial community,and the transformation between carbon components was completed by a variety of bacterial community.In conclusion,the addition of exogenous additives can improve OM degradation and promote microbial community succession.This study provides a new strategy to accelerate carbon conversion and reduce carbon emissions during dairy manure and bagasse pith composting,which is of great significance to improve composting quality.