Screening Of Garden Biomass Degrading Bacteria And The Compost Application

With the rapid development of urban greening construction,the output of garden waste continues to increase,and its efficient disposal and resource utilization of biomass is an important way to realize material recycling and green development.Among them,composting is one of the most convenient and practical disposal methods to realize the efficient utilization of garden waste.However,garden biomass composting faces basic application problems such as a long natural composting cycle,difficult degradation of lignocellulose,and uncertain dynamics of cracking of structural substances.To this end,this study screened degradable functional strains to explore their enzymatic properties and degradation mechanisms,and compounded them to form an enzymatic bacteria system for composting applications,in order to explore the chemical properties and structural depolymerization of the composting process.Dynamic changes.The specific research content and main results are as follows:(1)Using sodium carboxymethyl cellulose as the sole carbon source,degrading functional bacteria were screened from the natural understory humus layer.Through Congo red staining,filter paper disintegration and determination of cellulase(endonuclease,exonuclease,glucosidase)and total enzyme activity,the final screened strains with higher enzyme activity were QL-1 and QL-4.16SrDNA and ITS sequencing identified Pseudomonas mandelii and Aspergillus fumigatus,and constructed their phylogenetic tree based on their genetic relationship.(2)Explore the enzymatic properties of degrading strains.The enzyme production conditions of the strains were optimized by orthogonal experiment design of five factors and four levels.The analysis of variance showed that the setting of factor levels had a significant impact on the experimental results(P<0.05 or P<0.01);For the degradation of cellulose,the weight loss rates of Pseudomonas mandelii QL-1 and Aspergillus fumigatus QL-4 reached 9.87%and 14.52%respectively on the 15th day of the degradation experiment;the content of degraded substances in the system decays exponentially with time The degradation amount was fitted to a nonlinear regression equation,and the results showed that Aspergillus fumigatus QL-4 had a significant effect on the degradation of lignocellulose(P<0.1),which was in line with the first-order kinetic law;(3)Explore the degradation mechanism of degrading strains.Gas chromatography-mass spectrometry was used to quantify the content of lignin G-Lignin,S-Lignin and H-Lignin monomers in the degradation residue.The degradation rate of lignin monomer of Aspergillus fumigatus QL-4 reached 15.49%at 15 days;The structure difference between G-Lignin and S-Lignin monomer was used to analyze the effect of strains on the stability of lignin structure.The results show that QL-4 has a stronger effect on the depolymerization of lignin structure,and it plays an important role in the removal of methoxyl groups;by analyzing the changes in the molecular structure of lignin during the degradation process,it is inferred that there is a degradation of lignin β-aryl ether metabolic pathway.(4)Compound strains were screened for garden biomass composting treatment,and the original strains and the addition of rhamnolipids were used as two control treatments at the same time.By monitoring the changes of various physical and chemical properties during the composting process,the influence of external additives on composting was discussed.Composting results showed that,except for the blank CK group which was not mature,the other treatment groups all reached basic maturity within 40 days.Among them,the pH value,electrical conductivity,ammonium nitrogen,nitrate nitrogen,germination index,organic matter,total nutrients,heavy metals,and degradation rates of cellulose and lignin show different trends during the compost heating period,high temperature period and cooling period,and Due to the different treatments of composting strains,there are relative differences between the groups;the degradation rate of cellulose and lignin finally reached 9.14%～11.39%and 18.63%～22.34%;the three groups of compost substrates were all added with 4 different amounts The treatment was carried out,and the cultivation and planting experiment was carried out for 30 days in comparison with the garden soil.The results showed that the effects of composting substrates in each group on the cultivation and planting of muskmelon reached a significant level(P<0.05).The optimal addition amount of the original bacterial strain and the rhamnolipid control group was 50%,and the optimal addition amount of the compost substrate of the screening bacteria experimental group is 40%.