Determining the effect of acid stress on the persistence and growth of thermophilic microbial species after mesophilic colonisation of low grade ore in a heap leach environment

摘要

The microorganisms involved in the bioleaching of sulphidic mineral ores are acidophilic. Generally, a pH in the range of pH 1-2.5 is applied for optimal growth in these systems. In operating heaps, perturbation of conditions could result in changes in the pH outside this "safe" window, so an understanding of the effect of changes in pH on growth and activity of bioleaching microbes is needed. Previous work has shown that some microorganisms e.g. Acidithiobacillus thiooxidans, Leptospirillum ferriphilum and Lepto-spirillum ferrooxidans are able to adapt to low pH environments (~pH 0.9). However, most studies on the response of micro-organisms implicated in mineral bioleaching to pH have been conducted under submerged, aerated culture conditions, with limited performance-based studies conducted under conditions mimicking a heap environment. In this study, the effect of acid stress on the persistence of the thermophilic micro-organisms in the ore bed inoculated at mesophilic conditions and their subsequent growth on reaching thermophilic conditions is considered.