Biotransformation of Pingzhuang lignite by Penicillium oxalicume HM-M1

With the depletion of clean coal resources, lignite as a kind of low-rank coal has attracted more and more attention. Microbial transformation of lignite is a new technical means to prepare high-value chemicals from lignite, and the key is to separate and screen the microorganisms that can efficiently dissolve and transform lignite. In this study, one fungal strains called Penicillium oxalicume HM-M1 was isolated from Inner Mongolia′s Pingzhuang lignite mine and identified. The strain has the advantages of strong adaptability to lignite environment and high dissolution and transformation efficiency. The dissolution rate of pretreated lignite reached 50.3% in liquid medium at 28 ℃ and dissolved coal for 20 d. The elemental analysis and industrial analysis of coal samples were carried out, and the structure of lignite before and after microbial dissolution and transformation was analyzed by SEM and FTIR. Theresults show that the strain could grow under the condition of using lignite as the only nutrient source, and the lignite could be further dissolved into black fluid. Oxygen content in lignite increased after nitric acid oxidation treatment. At the same time, nitric acid treatment could transform some fixed carbon into volatile components through oxidative cleavage, which further improves the microbial dissolution and conversion rate of lignite. Theresult of SEM analysis showed that after dissolved and transformed by strain HM-M1, the lignite residue became corrosive, the lignite structure became loose and porous, and more lignite components were dissolved and converted into liquid. The result of FTIR analysis showed that the Penicillium oxalicume mainly degrades the O and N groups in lignite, such as carbonyl, carboxyl, amido, ether bond, etc. For GC-MS analysis, 10 kinds of high concentration biodissolution compounds were identified, including benzoic acid, phthalate esters, benzofuran, naphthalene, phenanthrene, etc. Nearly all of these compounds are useful fine chemical raw materials or pharmaceutical synthesis intermediateswith high application value. In this study, penicillium oxalicum was isolated from lignite for the first time and applied to the dissolution and transformation of lignite to prepare high-value chemicals.