Microorganisms have the potential to remove heavy metals from polluted waters and
effluents and may be used in clean-up processes. Microbial associations were enriched for
and adapted to grow in nutrient solutions containing various concentrations of different
metals. As immobilised cells are known to be more stable and more efficient in metal
uptake than are corresponding planktonic or free-living cells the attachment of the
microbial associations was investigated using a model stream and it was found that biofilm
development was better on rough surfaces such as ground glass and polystyrene than on
smooth surfaces such as unetched glass plates and glass beads. When comparing metal uptake
by planktonic and attached microorganisms, attached populations were found to
have a greater metal-uptake capacity. The uptake of individual metals from various metal
combinations was tested with various proportions of pregrown metal-adapted microbial
populations as inoculum and it was found that a particular metal was taken up more readily
by microbial associations which had previously been exposed to that metal. Lead (Pb2+)
appeared to be taken up more readily than copper (Cu2+) or cadmium (Cd2+) while Cd2+
was more actively removed than Cu2+ from solution. pH also affected metal uptake and
the optimum range for Cu2+ uptake by the Cu2+ -adapted microbial association was found
to be between 5.8 and 7.0. Dead microbial biomass was investigated and found to have
efficient metal uptake capacity. Living mycelium from an isolated Aspergillus species
showed poor uptake of Cu2+ initially, but when this fungus was pregrown and subsequently
killed by moist heat treatment the non-living mycelium was efficient in removal of Pb2+
and Cu2+ ions. The optimum mycelial biomass concentration for metal uptake was also
determined. The mechanism of metal uptake by this Aspergillus species was determined,
using electron microscopy and EDX techniques, to be metabolism-independent biosorption
onto the hyphal surface. Thus the microbial associations and fungal cultures used in this
study were shown to have the potential for use in the removal of heavy metals from
polluted waters. / Thesis (Ph.D.)-University of Natal, Pietermartizburg, 1995.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/9249 |
| Date | January 1995 |
| Creators | Meyer, Angela. |
| Contributors | Wallis, Mike. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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