Effect of pH values on extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

The effect of pH values on the extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans was comparatively investigated in different phases of bacterial growth during chalcopyrite bioleaching. The results indicate that the extracellular protein is always more than the extracellular polysaccharide secreted by attached cells on the chalcopyrite, on the contrary, and is always less than the extracellular polysaccharide secreted by free cells in the solution at bacterial adaptive phase, logarithmic phase and stationary phase whenever pH value is at 1.0, 1.5, 2.0 or 2.5; free cells are mainly through the secretion of extracellular polysaccharide rather than the extracellular protein to fight against disadvantageous solution environment, such as high concentration of metal ions and unsuitable pH solution; both amounts of polysaccharide and protein secreted by attached cells are mainly positively related to the solution acidity rather than the total concentration of soluble metal ions. The experimental results imply that bacteria are mainly through secreting more extracellular polysaccharide to fight against disadvantageous environment and the extracellular protein perhaps plays an important role in oxidation？reduction reactions in the bioleaching system.

甘氨酸亚铁结晶粒度和均匀性研究

试验研究搅拌速度、添加晶种、降温速度等因素对甘氨酸亚铁结晶粒度和均匀度的影响。结果表明：搅拌速度很大程度地影响晶体粒度及均匀度;添加晶种的结晶粒度是自然结晶粒度的5倍左右,乙醇结晶的粒度是自然结晶粒度的1.5~2倍,且二者的结晶粒度更大,均匀性更好;降温速度越快,晶体粒度越小,粒径分布越集中。