不同粘粒矿物对微生物利用木质素形成腐殖质差异性的影响

Humic substances (HS) was a product that formed with the soil abiotic and non abiotic process. The indispensible basic materials of HS formation could be provided by lignin. The studies about the microorganisms and their enzymes as biological catalysts participating in the transformation of lignin into HS were much more, whereas the research about minerals as non biological catalysts involving in the formation of HS based on the microbial utilization of lignin was only in its infancy. The questions about whether the catalysis from different types of mineral caused the differences in both composition and structure characteristics of HS and how the minerals acted as a catalyst were all unknown. In view of that, the liquid shake-flask method was adopt and cultured for a period of 110 days, in which the lignin served as a sole carbon source in the culture medium. The different types of clay minerals (kaolinite, montmorillonite, goethite, δ-MnO2 and bayerite) was introduced respectively, and then inoculated with a multiple species inoculant, which constituted a "three-membered cultural system". The research target focused on the dynamic changes of HS components and the molecular structure characteristics of humic acid (HA) respectively extracted from the microbial residue. That combining to the change in the composition of clay mineral surface functional groups could reveal the mechanism of minerals catalyzing the formation of HS. The relevant results would not only provide a theoretical basis for expounding the heterogeneous structure of humus and controling its forming pathway, but also provide a realistic basis for developing a more efficient decomposition agent of organic materials.

腐殖物质（HS）是伴随土壤生物与非生物过程所形成的产物，木质素可为其形成提供重要的基础材料。关于微生物及其酶系作为生物催化剂参与木质素向HS转化的研究较多，而对于矿物作为非生物催化剂参与木质素向HS转化的研究却很少。不同矿物类型所发挥的催化作用能否引起HS在组成和结构特征上的差异，矿物参与催化HS形成的机理和规律是什么，我们均不得而知。鉴于此，项目拟采用液体摇瓶培养法，在以木质素为碳源基质的培养液中分别引入不同类型的粘粒矿物（高岭石、蒙脱石、针铁矿、δ-MnO2和三羟铝石），再接种复合菌构成“三元培养体系”，进行为期110天的恒温培养。研究内容紧密围绕菌体残留物HS组分的动态变化以及胡敏酸（HA）分子的结构特征，并能结合粘粒矿物表面官能团组成的改变来揭示矿物催化HS形成的机理。相关研究成果既可为腐殖质异质结构的阐明及其形成途径的控制提供理论基础，还可为高效有机物料腐熟剂的研制提供现实依据。

腐殖化过程无法摆脱矿物而存在，为探明矿物对微生物驱动下木质素参与腐殖化进程的影响，采用液体摇瓶培养法，向添加高岭石、蒙脱石、针铁矿、δ-MnO2或三羟铝石的木质素培养液中接种复合菌剂，在110 d培养期间采用TOC分析仪、元素分析仪、FTIR、SEM、XRD、13C NMR及TG/DSC技术对细胞代谢产物的TOC含量，矿物-菌体残留物的回收率、腐殖质组成及提取类胡敏酸（HLA）的结构特性，矿物参与形成矿物-菌体残留物后的结构变化进行分析。结果表明：（1）针铁矿更易提高矿物-菌体残留物的回收率，蒙脱石作用最小。高岭石对细胞代谢产物中TOC含量促进作用最大，δ-MnO2作用最小；（2）δ-MnO2可促进矿物-菌体残留物HLA的形成，新形成的HLA分子结构相对简单。δ-MnO2和三羟铝石更易促进类富里酸（FLA）分子的缩合，使之向HLA转化。在积累类胡敏素（HLu）方面，δ-MnO2更具优势；（3）高岭石、蒙脱石对HLA分子中C、H和O+S含量的累积作用、对HLA缩合度的促进作用远低于铁铝锰氧化物。除三羟铝石外，其余4种矿物下形成的HLA分子中几乎不含氮，仅为腐殖质形成的前体物质；历经110 d培养，高岭石对HLA分子中糖类、羧酸及羟基的促进作用最大，间接改善HLA分子的氧化度，而蒙脱石相反。高岭石、蒙脱石和δ-MnO2更易促进HLA分子中芳香碳的分解，而针铁矿和三羟铝石则可提升其结构中的芳香碳比例，其中，针铁矿对HLA分子芳香度和不饱和度的促进作用最大，而蒙脱石最小；（4）参与形成矿物-菌体残留物后，高岭石结构水失衡，表面水化层多点形成氢键，Al‒OH发生脱羟作用。蒙脱石结构由团粒状变为片层状，结晶水收缩使层间结构遭到破坏，菌体胞外聚合物可与其表面官能团形成氢键，低角度衍射峰消失。针铁矿晶体结构出现大量纳米孔隙，表面结构水脱除，水合羟基与菌体间以氢键形式结合。δ-MnO2球状颗粒结合更加松散，表面结合水脱去，羟基与菌体发生缔合，低角度衍射峰发生轻微移动。三羟铝石晶粒轮廓更为清晰，表面OH-、A1-OH等活性基团与菌体以氢键形式结合。除蒙脱石外，其余4种矿物均未发生物相改变。