Analysis Of Lignocellulosic Degradation And Functional Bacterial Diversity In Surfactant Mediated Composting

With the rapid development of animal husbandry and agriculture in China,a large amount of animal excrement and straw waste are produced annually,which has a serious impact on the environment due to incorrect treatment.Not only that,but also caused the waste of agricultural resources.In order to solve the waste of resources and relieve the pressure on the environment,aerobic composting process is used to treat the solid organic waste,which can be converted into organic nutrient soil beneficial to crops through fermentation treatment.However,the traditional composting has the disadvantages of long fermentation time,slow lignocellulosic degradation and low humification degree.Therefore,how to improve the lignocellulosic degradation,humification process and speed up the degree of humification in the process of aerobic composting has become the main problem in the composting process.The purpose of this study was to investigate the effects of surfactant addition on physic-chemical parameters,organic matter(OM)biodegradation,community structure succession and metabolic function of related bacteria during composting.Non-ionic surfactant sucrose fatty acid ester(SE)was selected as additive to study its effect on the composting process of dairy manure and cassava residue.By comparing the experimental results,the thermophilic period in SE lasted for a longer time,the moisture was always maintained at about 65%,and the degradation rates of OM,dissolved organic matters(DOM)and lignocellulosic(16.34%,44.11% and 26.73%)were higher than those in CK(14.71%,39.11% and 19.90%).This indicated that the addition of SE was more conducive to the fermentation of composting.The content of humic substances(HS)in SE increased by 36.34% using total organic carbon analyzer,which was significantly higher than that in CK(17.68%).High-throughput sequencing showed that the relative abundances of Firmicutes and Actinobacteria in SE increased,while the relative abundance of Blastomonas decreased significantly.Redundancy analysis showed that Bacillus and Acinetobacter were positively correlated with temperature and OM,while Azomonas and Luteimonas were positively correlated with p H value,suggesting that the community structure of related bacteria could be optimized by adjusting relevant environmental factors.The effects of anionic surfactant 1-Hexadecylsulfonic acid sodium salt(SAS)and cationic surfactant N-Hexadecyl trimethyl ammonium Chloride(CTAC)on physico-chemical parameters,OM degrdation and bacterial metabolism in the composting process of dairy manure and bagasse were studied.In the case of the same other factors,compared with the CK,the experimental group had obvious advantages in the aspects of temperature,moisture,C/N,OM degradation and HS synthesis,especially the SAS had the highest efficiency.High-throughput sequencing showed that there were differences in bacterial community structure among the three groups.The mean values of OTUs in SAS and CTAC(1409,1428)were higher than those in CK(1308),indicating that surfactants could enrich species diversity.The relative abundances of Firmicutes and Proteobacteria in SAS and CTAC were higher,while the relative abundance of Actinobacteria in CK was higher.Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUST)indicated that amino acid metabolism and carbohydrate metabolism were the most important metabolic pathways during composting.The metabolic processes,environmental and genetic information processing processes and related genes in SAS and CTAC were more abundant than those in CK.Correlation analysis also showed that the dominant flora had a more significant correlation with environmental factors.In general,anionic surfactants perform better in composting.In conclusion,the addition of surfactants can prolong the thermophilic period of composting,increase moisture,enhance the stability of liquid film in the process of compost fermentation,providing a more favorable environment for the growth and metabolism of microorganisms,and thus improve the activity and relative abundance of related microorganisms.In addition,surfactant can also promote the biodegradation and transformation of OM,accelerate the formation of HS,and improve the composting maturity degree,so as to improve the quality of compost products.