Gardner M N, Rawlings D E
Department of Microbiology, University of Cape Town, Rondebosch, South Africa.
J Appl Microbiol. 2000 Jul;89(1):185-90. doi: 10.1046/j.1365-2672.2000.01117.x.
Considerably larger quantities of cyanide are required to solubilize gold following the bio-oxidation of gold-bearing ores compared with oxidation by physical-chemical processes. A possible cause of this excessive cyanide consumption is the presence of the enzyme rhodanese. Rhodanese activities were determined for the bacteria most commonly encountered in bio-oxidation tanks. Activities of between 6.4 and 8.2 micromol SCN min(-1) mg protein(-1) were obtained for crude enzyme extracts of Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Thiobacillus caldus, but no rhodanese activity was detected in Leptospirillum ferrooxidans. Rhodanese activities 2-2.5-fold higher were found in the total mixed cell mass from a bio-oxidation plant. T. ferrooxidans synthesized rhodanese irrespective of whether it was grown on iron or sulphur. With a PCR-based detection technique, only L. ferrooxidans and T. caldus cells were detected in the bio-oxidation tanks. As no rhodanese activity was associated with L. ferrooxidans, it was concluded that T. caldus was responsible for all of the rhodanese activity. Production of rhodanese by T. caldus in batch culture was growth phase-dependent and highest during early stationary phase. Although the sulphur-oxidizing bacteria were clearly able to convert cyanide to thiocyanate, it is unlikely that this rhodanese activity is responsible for the excessive cyanide wastage at the high pH values associated with the gold solubilization process.
与通过物理化学方法氧化相比，含金矿石生物氧化后需要大量得多的氰化物来溶解金。这种过量氰化物消耗的一个可能原因是存在硫氰酸酶。测定了生物氧化槽中最常见细菌的硫氰酸酶活性。氧化亚铁硫杆菌、氧化硫硫杆菌和嗜热硫杆菌的粗酶提取物的活性为6.4至8.2微摩尔硫氰酸盐每分钟每毫克蛋白质，但在氧化亚铁钩端螺旋菌中未检测到硫氰酸酶活性。在一个生物氧化厂的总混合细胞团中发现硫氰酸酶活性高2至2.5倍。氧化亚铁硫杆菌无论在铁上还是在硫上生长都会合成硫氰酸酶。使用基于聚合酶链反应的检测技术，在生物氧化槽中仅检测到氧化亚铁钩端螺旋菌和嗜热硫杆菌细胞。由于氧化亚铁钩端螺旋菌没有硫氰酸酶活性，得出的结论是嗜热硫杆菌是所有硫氰酸酶活性的原因。嗜热硫杆菌在分批培养中产生硫氰酸酶与生长阶段有关，在稳定期早期最高。虽然硫氧化细菌显然能够将氰化物转化为硫氰酸盐，但这种硫氰酸酶活性不太可能是与金溶解过程相关的高pH值下过量氰化物浪费的原因。
