Repository logo

Doctoral Degrees (Microbiology)

Permanent URI for this collectionhttps://hdl.handle.net/10413/8007

Browse

Browsing Doctoral Degrees (Microbiology) by Subject "Anaerobic bacteria--Industrial applications."

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Bioremediation of heavy metal polluted waters.
    (1995) Meyer, Angela.; Wallis, Frederick Michael.
    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.
  • Thumbnail Image
    Item
    Microbiological investigations into granular sludge from two anaerobic digesters differing in design and industrial effluent purified.
    (1995) Howgrave-Graham, Alan R.; Wallis, Frederick Michael.
    Due to a combination of selection criteria, sludges from upflow anaerobic digesters treating industrial waste waters consist primarily of well-settling, dense agglomerates called granules. Quantification of the component mixed microbial populations of these granules has been severely restricted by the inability of researchers to disrupt them without concomitantly destroying numerous cells. In situ quantification using light and electron microscopy is complicated by the high cell numbers and bacterial diversity; the small cell size; and the destructive nature of electron microscopy preparative techniques preventing the viewing of more than a small percentage of the population at a time. For these reasons, in this investigation, standardization of qualitative electron microscopic techniques was performed prior to their application to granules. Isolation and electron and light microscopic techniques were applied to granules from a fullscale clarigester treating effluent from a maize-processing factory. In addition, a method using montaged transmission electron micrographs (TEMs) taken along a granule radius, and image analysis, was developed for bacterial quantification within granules. This method, together with antibody probe quantification, was applied to granules from an upflow anaerobic sludge blanket (UASB) digester treating a brewery effluent. The clarigester granules contained a metabolically and morphologically diverse population of which many members were not isolated or identified. By contrast, the UASB digester granules consisted primarily of morphotypes resembling Methanothrix, Methanobacterium and Desulfobulbus, in order of predominance. However, only about one-third of the population reacted with antibody probes specific to strains of bacterial species expected to occur within these granules. According to the antibody probe library used, the Methanobacterium-like cells observed in TEMs were probably Methanobrevibacter arboriphilus. From this study it is apparent that different anaerobic digester designs, operational parameters, and the chemical composition of the waste water purified, are factors which influence the formation and maintenance of granules differing with respect to their microbial populations. Until the difficulties associated with quantification are overcome, the processes governing granule formation and/or population selection will remain obscure.