Han CJ, Kelly RM
Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, USA.
Biotechnol Bioeng. 1998 Jun 20;58(6):617-24. doi: 10.1002/(sici)1097-0290(19980620)58:6<617::aid-bit7>3.0.co;2-l.
The biooxidation capacity of an extremely thermoacidophilic archaeon Metallosphaera sedula (DSMZ 5348) was examined under bioenergetic challenges imparted by thermal or chemical stress in regard to its potential use in microbial bioleaching processes. Within the normal growth temperature range of M. sedula (70-79 degrees C) at pH 2.0, upward temperature shifts resulted in bioleaching rates that followed an Arrhenius-like dependence. When the cells were subjected to supraoptimal temperatures through gradual thermal acclimation at 81 degrees C (Han et al., 1997), cell densities were reduced but 3 to 5 times faster specific leaching rates (Fe3+ released from iron pyrite/cell/h) could be achieved by the stressed cells compared to cells at 79 degrees C and 73 degrees C, respectively. The respiration capacity of M. sedula growing at 74 degrees C was challenged by poisoning the cells with uncouplers to generate chemical stress. When the protonophore 2,4-dinitrophenol (5-10 μM) was added to a growing culture of M. sedula on iron pyrite, there was little effect on specific leaching rates compared to a culture with no protonophore at 74 degrees C; 25 μM levels proved to be toxic to M. sedula. However, a significant stimulation in specific rate was observed when the cells were subjected to 1 μM nigericin (+135%) and 2 μM (+63%); 5 μM levels of the ionophore completely arrested cell growth. The ionophore effect was further investigated in continuous culture growing on ferrous sulfate at 74 degrees C. When 1 μM nigericin was added as a pulse to a continuous culture, a 30% increase in specific iron oxidation rate was observed for short intervals, indicating a potential positive impact on leaching when periodic chemical stress is applied. This study suggests that biooxidation rates can be increased by strategic exposure of extreme thermoacidophiles to chemical or thermal stress, and this approach should be considered for improving process performance. Copyright 1998 John Wiley & Sons, Inc.
在热应激或化学应激所带来的生物能量挑战条件下，对极端嗜热嗜酸古菌嗜热栖热硫化叶菌（DSMZ 5348）的生物氧化能力进行了检测，以探究其在微生物生物浸出过程中的潜在用途。在嗜热栖热硫化叶菌正常生长温度范围（70 - 79摄氏度）、pH值为2.0的条件下，温度升高导致生物浸出速率呈现出类似阿累尼乌斯定律的依赖关系。当通过在81摄氏度下逐步热适应使细胞处于超适温度时（Han等人，1997），细胞密度降低，但与79摄氏度和73摄氏度的细胞相比，处于应激状态的细胞的比浸出速率（从黄铁矿释放的Fe3 + /细胞/小时）分别快3至5倍。通过用解偶联剂毒害细胞以产生化学应激，对在74摄氏度下生长的嗜热栖热硫化叶菌的呼吸能力进行了挑战。当将质子载体2,4 - 二硝基苯酚（5 - 10μM）添加到以黄铁矿为生长底物的嗜热栖热硫化叶菌培养物中时，与74摄氏度下未添加质子载体的培养物相比，对比浸出速率几乎没有影响；25μM的浓度被证明对嗜热栖热硫化叶菌有毒。然而，当细胞受到1μM尼日利亚菌素（+ 135%）和2μM（+ 63%）处理时，对比速率有显著提高；5μM的离子载体水平完全抑制了细胞生长。在以硫酸亚铁为底物、74摄氏度下的连续培养中进一步研究了离子载体的作用。当向连续培养物中脉冲添加1μM尼日利亚菌素时，在短时间内观察到比铁氧化速率增加了30%，这表明当施加周期性化学应激时，对浸出可能有积极影响。本研究表明，通过将极端嗜热嗜酸菌有策略地暴露于化学或热应激下，可以提高生物氧化速率，并且应考虑采用这种方法来改善工艺性能。版权所有© 1998 John Wiley & Sons, Inc.
