Study On Humic Substances Formation By Different Microorganisms Utilizing Organic Materials Like Sugar And Cyanobacteria

The progressive deterioration of global soil quality aroused particularly concerning about the soil resource condition, to improve soil organic matter content continually and implement effective management are the important way to cope with the deterioration trouble. As the main part of the soil organic matter, humic substances have significant influences on the quality and quantity of SOC. Organic materials and microorganisms are the pivotal material basis of humic substances formation, the humification effects and humus composition and structure are directly related to the degree of different microbial utilizing different organic materials. In view of the different effects of different microorganisms on humus formation based on the microbial utilization of carbohydrates and cyanobacteria in liquid pure culture condition and of corn stover in soil culture condition, in this research, the methods of shake-flask liquid pure culture and long-term soil simulation experiments were adopted to study the characteristics of thallus sediments and extracellular metabolisms produced by bacteria, actinomyces and fungi with glucose, cellulose and cyanobacteria, the dynamic effect law of quantity and forming sequence of HS fraction formed by different microbial with corn straw added into Dark Brown soil, at the same time, to explore the possibility of cyanobacteria spontaneously formed humus and the alkali extraction products features of different natural organic materials. The relevant conclusions were as follows:(1) Under liquid culture conditions, the extracellular metabolisms produced by microorganisms with organic materials had simple structure, the structure of thallus sediments was more complex but there still existed certain gaps between thallus sediments and standard humic acids. There were less aromatic, carboxyl and carbonyl carbon contens, more polysaccharide components in thallus sediments when glucose was used as carbon source.Actinomyces and fungi could utilize glucose to promote the transformation of simple organic matters into complex matters. More aromatic rings and unsaturated carbon chain were synthesized by Streptomyces prunicolor with glucose, the thallus sediment structure was more "mature"; more stable and long fatty hydrocarbon chains were synthesized by Brevibacterium sp.with glucose, the thallus sediments had high saturation and low maturity. The thallus sediments produced by microorganisms with cellulose had more simple structures than that with glucose.Structures of Brevibacterium sp. and Trichoderma viride thallus sediments were more complex,the two strains could synthetic complex macromolecular organic compounds after degradationof cellulose, Structures of Penicillium, Streptomyces sp. and Bacillus megaterium thallus sediments were were much simple, which were the degradation products of cellulose.(2) This study figured out the corresponding relation between thallus sediments composition and alkali extraction components, and defined two indicators of the efficiency and the degree of transformation. Considering the two indicators comprehensively, we found that the metabolites produced by Streptomyces prunicolor and Streptomyces sp. had low relative contents but high complexity and strong stability, the characteristic of Streptomyces prunicolor was especially prominent. The features of thallus sediments produced by Brevibacterium sp. and Bacillus megaterium were opposite. The water-soluble components content of metabolites produced by fungi with cellulose was more than by other microbe, metabolites produced by Trichoderma viride had more relative contents and higher complexity than that by Penicillium.(3) The possibility of cyanobacteria spontaneously formed humus was very low, but there were some complex organic substances produced in growth periods, which provide material conditions for humus formation. Relative to the humus, thallus of cyanobacteria had more organic nitrogen and less organic carbon, high contents of protein and polysaccharide. The extracellular metabolism contained a large number of hydroxy and carboxyl functional groups,and the structure of intracellular metabolites was more complicated than that of extracellular metabolites. The aromaticity of thallus in late logarithmic and decay phases was higher, which was closer to the complexity of fulvic acid.(4) Under liquid culture condition, the aromaticity of thallus sediments produced by microorganisms with cyanobacteria as the sole carbon sources reduced, the degree of oxidation rised, and the structure was simpler. Cyanobacteria, especially that under decline phase could be decomposed by microbial, in which the degradation ability of soil leachate with a complex microbial was the strongest, followed by bacteria and actinomycetes, the thallus sediments produced by fungi with cyanobacteria were the most complex.(5) Microorganisms could obviously promote the humification of the amended organic materials in soil, and there was time effect belong that. The effects on humic acids relative contents of fungi and actinomycetes were remarkable greater than that of bacteria. Microbial treatments did benefit to the synthesis of HA, and there was great possibility that FA turned into HA, which was embodied in the transformation of C and N elements. Actinomycetes affected the structure of humic acids mainly by C=O bond, bacteria and fungi played major roles on the N and H contents of the humic acids, respectively.(6) The total organic carbon contents of natural biomaterials were higher than that of soil.Compared with soil samples, the water-soluble components and alkali insoluble componentscontents in alkali extraction of natural biomaterials components were obviously high, and the alkali extracted components content was significantly low. There were differences between different natural biomaterials alkali extraction components and soil humus. The alkali extraction components of natural biomaterials were not humus.In general, there were differences in effects of different microorganisms with organic carbon sources under liquid culture conditions, the effects results were complex, different from that under soil culture conditions. The humification degree of microorganism with glucose was higher than that with cyanobacteria and cellulose. The humification process of glucose was a synthetic process, the humification process of cellulose had degradation and synthesis stages,the cyanobacteria humification process was the degradation of residual. The research had solved some unknown problems in liquid culture, comprehensively discussed the microbial effect and time effect of organic materials humification in long-term soil culture, and explored the role of cyanobacteria in humus origin, provided deep understanding of the biochemistry process of humus formation and origin.