【作者】 符波；

【导师】 周洪波；

【作者基本信息】 中南大学 ， 生物工程， 2007， 硕士

【摘要】 生物冶金技术是一种从矿物中提取金属的经济方法，特别适于处理贫矿、表外矿及废矿，并具有成本低、投入小、能耗低、对环境污染小等突出优点。在本文研究中，四株嗜酸硫氧化细菌得到分离纯化和鉴定。为了研究硫氧化细菌在硫化矿浸出中的作用以及是否通过氧化浸出过程中产生的单质硫来提高浸出率，本文主要从硫氧化细菌的分离和鉴定出发，重点研究了嗜铁钩端螺旋菌（Leptospirillum ferriphilum）和氧化亚铁硫杆菌（Acidithiobacillus ferrooxidans）这两株铁氧化细菌以及它们与硫氧化细菌混合对黄铜矿的浸出，同时考察了黄铜矿浸出过程中黄钾铁矾的作用，并讨论了以上四种细菌浸出黄铜矿的机理。从煤矿废水中分离得到四株硫氧化细菌S₂，AA011，AA012和DMC。中度嗜热硫氧化细菌S₂为革兰氏阴性细菌，短杆状，可运动，菌体大小为（0.4～0.6）μm×（1～2）μm。最适生长温度在42℃～45℃之间，最适初始生长pH为2.5。三株嗜温硫氧化细菌AA011，AA012和DMC为可运动的短杆状革兰氏阴性细菌，菌体大小为（0.4～0.7）μm×（1～2）μm。最适生长温度在30℃之间，最适初始生长pH为2.0～2.5。四株细菌均可利用硫磺、四硫酸盐、硫代硫酸盐为能源进行化能自养型生长，不能利用蛋白胨、葡萄糖、酵母粉等有机物以及，也不能进行混合型生长对分离菌株进行了形态、生理生化特性研究及16S rRNA序列分析。这三株细菌均为革兰氏阴性细菌，短杆状，化能自养，可利用单质硫、四硫酸盐、硫代硫酸盐为能源生长，不能利用蛋白胨、葡萄糖、酵母粉等有机物以及硫酸亚铁、黄铁矿、黄铜矿等为能源生长。根据细菌形态特征、生理生化特征和以16S rDNA序列同源性为基础构建的系统发育树分析，结果表明菌株S₂与喜温硫杆菌（Acidithiobacillus caldus）处于同一进化树分支中，菌株AA011，AA012和DMC与氧化硫硫杆菌（Acidthiobacillus thiooxidans）处于同一进化树分支中，基因序列相似性均大于99％。当菌株S₂分别与嗜铁钩端螺旋菌（Leptospirillum ferriphilum）和氧化亚铁硫杆菌（Acidithiobacillus ferrooxidans）混合浸出黄铜矿时，铜浸出率与铁氧化细菌纯培养物相比分别提高56.8％和10％。嗜铁钩端螺旋菌和喜温硫杆菌混合浸出的黄铜矿矿渣的电子扫描显微镜照片显示黄铜矿表面受到细菌的严重蚀刻。各浸矿体系的矿渣的X-衍射分析表明喜温硫杆菌具有通过氧化浸矿过程中产生的硫从而促进黄铜矿浸出的作用。利用氧化亚铁硫杆菌、氧化硫硫杆菌、嗜铁钩端螺旋菌和喜温硫杆菌四种细菌的纯培养物和混合菌进行黄铜矿摇瓶浸出实验。实验结果表明铁氧化细菌与硫氧化细菌混合浸出黄铜矿的效率高出铁氧化细菌纯培养物单独浸出时4.4％-13.9％。硫氧化细菌的存在能有效促进黄铜矿的浸出速率和浸出率。中度嗜热的嗜铁钩端螺旋菌和喜温硫杆菌混合菌的浸出效率比嗜温的氧化亚铁硫杆菌混合菌高出大约8.6％-18％。在含有氧化亚铁硫杆菌的浸出体系中，黄铜矿浸出速率在浸出12-16天后开始下降，这与浸出过程中在矿物表面形成的钝化膜黄钾铁矾有关。嗜铁钩端螺旋菌的纯培养物以及混合菌浸出体系的低pH则大大减少了黄钾铁矾的形成。更多还原

【Abstract】 Bioleaching is an economical method for the recovery of metals fromminerals, especially from low grade ores, overburden and waste from currentmining operations, which requires moderate capital investment with lowoperating cost. Furthermore, bioleaching are generally more environmentallyfriendly than conventional metal recovery processes such as concentration andsmelting. In the present study, four strains of acidophilic sulfur-oxidizingbacteria was isolated and characterized. To understand the role sulfur-oxidizingbacteria plays in mineral bioleaching and whether they enhance the dissolutionof metal sulfides by oxidizing S⁰ formed on the surface during the leachingprocess, we focused on the effects of two pure iron-oxidizing cultures（Leptospirillum ferriphilum or Acidithiobacillus ferrooxidans） and theircombination with the sulfur-oxidizing bacteria on copper dissolution fromchalcopyrite. The role of jarosite precipitation in the bioleaching ofchalcopyrite was also investigated, and the bioleaching mechanisms ofchalcopyrite by the above four bacterial species were discussed.Four strains of acidophilic sulfur-oxidizing bacteria named as S2, AA011,AA012 and DMC were isolated from coal heap drainage. A moderatelythermophilic bacterium named S₂ is motile, Gram-negative, and rod-shaped,measures 0.4 to 0.6 by 1 to 2μm, and grows optimally at 42-45℃and aninitial pH 2.5. Three strains of mesophilic bacteria AA011, AA012 and DMCare motile, Gram-negative, rod-shaped, and measures 0.4 to 0.7 by 1 to 2μm.They grow optimally at 30℃and initial pH 2.0-2.5. The four strains growautotrophically by using elemental sulfur, sodium thiosulfate and potassiumtetrathionate as energy sources. The strains can not use organic matter andinorganic minerals including ferrous sulfate, pyrite and chalcopyrite as energysources. The morphological, biochemical and physiological characterizationand analysis based on 16S rRNA gene sequence indicated that the strain S₂ ismost closely related to Acidithiobacillus caldus and that the strains AA011,AA012 and DMC are most closely related to Acidithiobacillus thiooxidans（＞99% similarity in gene sequence）.The combination of the strain S₂ with L. ferriphilum or A. ferrooxidans inchalcopyrite bioleaching improved the copper leaching efficiency. Compared with the pure iron-oxidizing culture, percentage copper release of the mixedculture increased 50.6% （L. ferriphilum） and 10% （A. ferrooxidans）respectively. Scanning electron microscope（SEM） analysis revealed that thechalcopyrite surface in a mixed culture of L. ferriphilum and A. caldus washeavily etched. The energy dispersive X-ray （EDX） analysis indicates that A.caldus has the potential role to enhance the recovery of copper fromchalcopyrite by oxidizing the sulfur formed during the bioleaching progress.The bioleaching of chalcopyrite in shake flasks was investigated withpure and mixed cultures of A. ferrooxidans, A. thiooxidans, A. caldus and L.ferriphilum. The mixed cultures containing both iron- and sulfur-oxidizingbacteria were more efficient than the pure culture alone. The presence ofsulfur-oxidizing bacteria positively increased the dissolution rate and thepercentage recovery of copper from chalcopyrite. An increase of 4.4% to13.9% in percentage recovery of copper was reached. Mixed culturesconsisting of moderately thermophilic L. ferriphilum and A. caldus leachedchalcopyrite more effectively than mesophilic A. ferrooxidans mixed cultures（8.6%-18% higher percentage recovery of copper）. The decrease ofchalcopyrite dissolution rate in leaching systems containing A. ferrooxidansafter 12-16 days coincided with the formation of jarosite precipitation on themineral surface during the bioleaching as a passivation layer. Low pHsignificantly reduces jarosite formation in pure and mixed cultures of L.ferriphilum and A. caldus.更多还原