我国低阶煤储量十分丰富，但低阶煤热值低、水分高、挥发分高、易自燃，直接燃烧效率低，污染严重。目前的深加工方法主要有热转化法和微生物降解转化法，其中热解、气化和液化等热转化方法存在能耗高、设备复杂的缺点。煤的微生物降解则是利用微生物的生化作用将煤炭转化为液体燃料或高附加值的化学品的一种新途径，具有反应条件温和、设备要求简单、能耗低等优点。煤的微生物降解转化研究至今已开展了四十余年，也取得了不少成果，但仍存在降解率低，降解时间长，降解机理不明晰等问题，还需进行大量的研究工作。

本文选用了花土沟游动微菌、多噬香鞘氨醇单胞菌、恶臭假单胞菌和枯草芽孢杆菌枯草亚种四种细菌，以及硬毛栓孔菌、新硬毛革耳、疣孢漆斑菌和黄孢原毛平革菌四种真菌对新疆大南湖低阶煤进行降解实验。通过单因素和正交试验确定了大南湖煤微生物降解的最佳工艺条件，利用多种方法表征了降解液相产物和固相产物。探究了六种螯合剂作用下细菌降解大南湖煤的降解过程。借助代谢组学的方法揭示了优势细菌花土沟游动微菌对大南湖煤的降解机理。同时，还通过蛋白组学技术和煤的模型化合物研究了优势真菌硬毛栓孔菌对大南湖煤的降解机理。本论文的具体工作如下：

(1) 四种细菌和四种真菌降解大南湖低阶煤的条件及产物分布研究

通过单因素和正交试验确定了四种细菌降解大南湖煤的最佳工艺条件为：煤浆浓度均为0.5 g/50 mL、菌液接种量在5-7 mL/50 mL之间、培养温度均为30 °C，降解时间均为15 天。花土沟游动微菌、多噬香鞘氨醇单胞菌、恶臭假单胞菌和枯草芽孢杆菌枯草亚种四种细菌在各自最佳工艺条件下对大南湖低阶煤的降解率分别为46.85%、41.62%、35.61%和37.12%。通过单因素和正交试验确定了四种真菌降解大南湖低阶煤的最佳工艺条件为：煤浆浓度均为0.6 g/50 mL、菌液接种量在8-10 mL/50 mL之间、培养温度均为30 °C，降解时间均为18天。硬毛栓孔菌、新硬毛革耳、疣孢漆斑菌和黄孢原毛平革菌四种真菌在各自最佳工艺条件下对大南湖低阶煤的降解率分别为75.05%、39.69%、70.54%和50.94%。四种细菌和四种真菌降解大南湖低阶煤的液相产物中含有大量的小分子有机物，分子量在85.05-546.79之间，主要有醇类、羧酸类、醛类、酮类、芳香烃和脂肪烃。细菌和真菌的作用使得大南湖低阶煤碳和硫含量降低，羧基和醚键被降解。细菌使煤样碳结构的石墨化程度增加，微晶结构的有序度增加而真菌能破坏煤的芳香结构和芳香层之间的连接。同时，细菌和真菌作用使煤的比表面积增大，煤结构中出现新的小孔和微孔。热重结果说明细菌和真菌确实对大南湖低阶煤的大分子结构产生了破坏作用，C_al-O、C_al-C_al、C_ar-O和C_ar-C_al等化学键被降解。

(2) 六种螯合剂对四种细菌降解大南湖低阶煤的促进作用研究

探究了六种螯合剂 (AO、EDTA、CA、IDS、GLDA和MGDA) 对四种细菌 (花土沟游动微菌、多噬香鞘氨醇单胞菌、恶臭假单胞菌和枯草芽孢杆菌枯草亚种) 降解大南湖低阶煤的影响。AO、IDS、GLDA和MGDA这四种螯合剂的添加都能促进四种细菌对大南湖低阶煤的降解。在六种螯合剂中，GLDA对恶臭假单胞菌降解大南湖低阶煤的促进作用最为显著，在最佳工艺条件下，添加3 mM的GLDA能使降解率从39.66%提高到了81.46%，降解时间从14天缩短为2天。在大南湖低阶煤降解过程中，添加的螯合剂与金属离子结合，破坏煤中的配位键，碱性物质和四种细菌分泌的其它活性物质主要作用于羧基和醚键等。因此，螯合剂的加入使其能够与微生物分泌的其它活性物质协同降解大南湖低阶煤，极大提高降解率和缩短降解时间。

(3) 利用代谢组学方法研究优势细菌花土沟游动微菌对大南湖低阶煤的降解机理

花土沟游动微菌所分泌的代谢产物是降解大南湖低阶煤的主要物质。采用代谢组学方法对添加大南湖低阶煤后的花土沟游动微菌的代谢产物进行了鉴定。结果表明，与花土沟游动微菌的代谢产物相比，共鉴定出43种上调和38种下调的代谢产物。发现花土沟游动微菌分泌的6种目标代谢产物，即碱性物质 (氨、酪胺、N-(5-氨基戊基)乙酰胺、L-左旋肉碱、甜菜碱) 和螯合剂 (柠檬酸盐) 对大南湖低阶煤具有降解特性。因此，花土沟游动微菌对大南湖低阶煤的降解过程中存在碱降解途径和螯合剂降解途径。这6种目标代谢产物作用于大南湖低阶煤中的酯键、醚键和配位键，将大南湖低阶煤的大分子结构解聚为醇、醛和酮等液体有机分子。

(4) 利用蛋白组学技术和煤的模型化合物探究优势真菌硬毛栓孔菌对大南湖低阶煤的降解机理

硬毛栓孔菌分泌的胞外酶是降解大南湖低阶煤的主要物质。硬毛栓孔菌分泌的3种木质素降解酶的酶活由强到弱为锰过氧化物酶>漆酶>木质素过氧化物酶。利用蛋白组学对添加大南湖低阶煤后的硬毛栓孔菌分泌的蛋白质进行了鉴定，检测结果表明，与硬毛栓孔菌分泌的蛋白质相比，共有110种上调和81种下调的蛋白质。所有差异蛋白中，芳醇脱氢酶和草酸氧化酶证明了硬毛栓孔菌所分泌的三种胞外木质素降解酶参与到了大南湖低阶煤的降解过程中。同时，羧酸酯水解酶、醛酮还原酶、(4-O-甲基)-D-葡萄糖醛酸-木质素酯酶和β-木聚糖酶也可能与大南湖低阶煤的降解有关。硬毛栓孔菌对6种煤的模型化合物的作用强度从大到小依次为二苯醚>苯甲酸乙酯>萘>吡啶>喹啉>苯甲酸。这说明醚键、酯键和稠环芳烃更易受到硬毛栓孔菌的攻击。6种煤的模型化合物与木质素过氧化物酶、锰过氧化物酶和漆酶的结合能均为负值，说明分子间的作用以及对接过程可以自发进行。

China has rich reserves of low-rank coal, but low-rank coal has the characteristics of low calorific value, high moisture content, high volatile content, and easy spontaneous combustion resulting in low combustion efficiency and severe pollution. Currently, the main deep processing methods are thermal conversion and microbiological degradation. Among them, thermal conversion methods such as pyrolysis, gasification, and liquefaction have the disadvantages of high energy consumption and complex equipment. Microbiological degradation of coal is a new way to utilize low-rank coal at normal temperature and pressure, and the degradation process is green and pollution-free. The research on microbiological degradation and conversion of coal has been carried out for more than 40 years, and has achieved certain results, but there are still problems such as low degradation rate, long degradation time, and unclear degradation mechanism. Therefore, a lot of research work is still needed.

In this paper, four kinds of bacteria, P. huatugouensis, S. polyaromaticivorans, P. putida and B. subtilis subsp. subtilis, and four kinds of fungi, T. trogii, P. neostrigosus, M. verrucaria and P. chrysosporium, were selected for the degradation of Xinjiang Dananhu low-rank coal. The optimal process conditions for microbial degradation of Dananhu low-rank coal were determined through single-factor and orthogonal experiments, and multiple methods were used to characterize liquid phase and solid phase degradation products. The degradation process of Dananhu low-rank coal by bacteria under the action of six chelating agents was explored. The degradation mechanism of predominant bacterium, P. huatugouensis, for Dananhu low-rank coal was revealed by using metabolomics. At the same time, the degradation mechanism of predominant fungus, T. trogii, for Dananhu low-rank coal was studied by using proteomics technology and model compounds of coal. The specific work of this thesis is as follows:

(1) Study on conditions and product distributions of Dananhu low-rank coal degraded by four bacteria and four fungi

The optimal process conditions for the degradation of Dananhu low-rank coal by four bacteria were determined through single-factor and orthogonal experiments and the optimal process conditions are: the pulp density of 0.5 g/50 mL, the bacterial inoculation quantity in the range of 5-7 mL/50 mL, the incubation temperature of 30 °C, the degradation time of 15 days. The degradation rates of Dananhu low-rank coal by four bacteria including P. huatugouensis, S. polyaromaticivorans, P. putida and B. subtilis subsp. subtilis, under their corresponding optimal conditions were 46.85%, 41.62%, 35.61%, and 37.12%. The optimal process conditions for the degradation of Dananhu low-rank coal by four fungi were determined through single-factor and orthogonal experiments and the optimal process conditions are: the pulp density of 0.6 g/50 mL, the fungal inoculation quantity in the range of 8-10 mL/50 mL, the incubation temperature of 30 °C, the degradation time of 18 days. The degradation rates of Dananhu low-rank coal by four fungi including T. trogii, P. neostrigosus, M. verrucaria and P. chrysosporium, under their corresponding optimal conditions were 75.05%, 39.69%, 70.54% and 50.94%. The liquid-phase products of Dananhu low-rank coal degraded by the four bacteria and four fungi contained a large amount of small organic molecules with a molecular weight between 85.05-546.79, mainly including alcohols, carboxylic acids, aldehydes, ketones, aromatic hydrocarbons, and fatty hydrocarbons. The actions of bacteria and fungi reduced the carbon and sulphur content of Dananhu low-rank coal and degraded the carboxyl and ether bonds. Bacteria increased the degree of graphitization of coal carbon structure and the order degree of microcrystalline structure, while fungi could disrupt the connection between the aromatic structure and the aromatic layer of coal. At the same time, the action of bacteria and fungi increased the specific surface area of coal and created new small and micro pores in the coal structure. The TG results showed that the four bacteria and four fungi did indeed damage the macromolecular structure of Dananhu low-rank coal, and chemical bonds such as C_al-O, C_al-C_al, C_ar-O and C_ar-C_al were degraded, promoting the thermal decomposition reaction of coal.

(2) Study on the promoting effects of six chelating agents on the degradations of Dananhu low-rank coal by four bacteria

The effects of six chelating agents (AO, EDTA, CA, IDS, GLDA and MGDA) on the degradation of Dananhu low-rank coal by four species of bacteria (P. huatugouensis, S. polyaromaticivorans, P. putida and B. subtilis subsp. subtilis) were investigated. The addition of chelating agents AO, IDS, GLDA, and MGDA could promote the degradation of Dananhu low-rank coal by the four bacteria. Among the six chelating agents, GLDA showed the most significant promotion effect on the degradation of Dananhu low-rank coal by P. putida, and under the optimal process conditions, the addition of 3 mM GLDA increased the degradation rate from 39.66% to 81.46%, and shortened the degradation time from 14 days to 2 days. During the degradation of Dananhu low-rank coal, the added chelating agent combined with metal ions, breaks the coordination bonds in coal, and the alkaline substances and other active substances secreted by the four bacteria mainly act on carboxyl and ether bonds. Therefore, the addition of chelating agents enables them to synergistically degrade Dananhu low-rank coal with other active substances secreted by microorganisms, greatly improving the degradation rate and shortening the degradation time.

(3) The degradation mechanism of Dananhu low-rank coal by predominant bacterium, P. huatugouensis used by metabolomics method

The metabolites secreted by the P. huatugouensis were the main substances for the degradation of Dananhu coal. The metabolomics approach was used to identify the metabolites of P. huatugouensis after addition of Dananhu low-rank coal. The results indicated that 43 upregulated and 38 downregulated metabolites were identified compared to the metabolites of P. huatugouensis alone. 6 target metabolites secreted by P. huatugouensis, which were alkaline substances (Ammonia, Tyramine, N-acetylcadaverine, L-carnitine, Betaine) and chelator (Citrate), were found to have biodegradation activities on Dananhu low-rank coal. Hence, there were alkali pathway and chelator pathway in the degradation process of Dananhu low-rank coal. The above 6 target metabolites could act on the ester, ether, and metal linkages of Dananhu low-rank coal to depolymerize macromolecular structure into liquid organic molecules such as alcohols, aldehydes and ketones.

(4) The degradation mechanism of Dananhu low-rank coal by predominant fungus, T. trogii used by proteomic method and model compounds of coal

The extracellular enzymes secreted by T. trogii were the main substances for the degradation of the Dananhu low-rank coal. The enzymatic activities of the three lignin-degrading enzymes secreted by T. trogii were manganese peroxidase > laccase > lignin peroxidase. The proteomic method was used to identify the proteins secreted by T. trogii after addition of Dananhu low-rank coal. The results showed that 110 upregulated and 81 downregulated proteins were identified compared to the proteins of T. trogii alone. Among all differentially expressed proteins, aryl-alcohol dehydrogenase and bicupin oxalate oxidase demonstrated that the three extracellular lignin degrading enzymes secreted by T. trogii were involved in the degradation process of Dananhu low-rank coal. Meanwhile, carboxylic ester hydrolase, aldo/keto reductase, (4-O-methyl)-D-glucuronate-lignin esterase, and β-xylanase may also be related to the degradation of Dananhu low-rank coal. The degradation abilities of T. trogii to six model compounds, in descending order, were: diphenyl ether > ethyl benzoate > naphthalene > pyridine > quinoline > benzoic acid. This indicated that ether bond, ester bond and thick-ringed aromatic hydrocarbons were more susceptible to attack by T. trogii. The binding energy of the six model compounds of coal with lignin peroxidase, manganese peroxidase and laccase were all negative, indicating that the intermolecular interaction and docking process could proceed spontaneously.

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