Article Abstract:
Saccharomyces cerevisiae has a high-affinity Mn2+/H+ antiport system for Mn2+ transport at low Mn2+ concentrations and a low-affinity transport system at high Mn2+ concentrations. The high-affinity system has a K(sub m) of 0.3 micro-M and is competitively suppressed by ions such as Mg2+ and Zn2+. The low-affinity system has a K(sub m) of 62 micro-M and is non-competitively suppressed by Mg2+. The low-affinity system is more specific for Mn2+ ions than the high-affinity system. The transport of Mn2+ in the presence of toxic concentrations of Mn2+ has a negative value of K(sub m).
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Article Abstract:
The accumulation of cadmium on biofilms was investigated using biofilms with pure- and mixed-cultures of sulphur bacteria to determine the factors that affect the uptake of this heavy metal. Results reveal that cadmium is localized on the superficial layer of the biofilm and that the degree of heavy metal adsorption is correlated with the presence of polysaccharides indicating that accumulation takes place via entrapment or precipitation. Biofilms with mixed cultures were more efficient in accumulating cadmium.
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Article Abstract:
The use of factorial methods to clarify significant variables and a response-surface analysis to ferret out more details was found to be effective in providing information useful to process optimization as well as efficient in making use of experimental results. This experimental approach was applied in studying the effect of process variables on alkalization and elimination of contaminating toxic metals from a simulated acid leachate by continuous mixed cultures of sulphate-reducing bacteria.
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