Browsing by Author "Rossouw, Johann Herman"

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    Assessing the capacity for micropollutants to induce changes in the biofilm EPS composition and yield
    (Stellenbosch : Stellenbosch University, 2021-12) Rossouw, Johann Herman; Wolfaardt, Gideon M.; Stone, Wendy; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: A consequence of widespread chemical manufacturing and usage is the increasing presence of a new class of contaminant: micropollutants. Despite the investment of significant resources into the development of novel approaches to wastewater treatment, the removal efficiency of micropollutants has been varied and conflicting between different studies. A notable gap in current research efforts is assessing the capacity for chronic micropollutant exposure to alter the main mechanisms contributing to their removal in secondary wastewater treatment. The aim of this study was three-fold. First, to investigate the comparative homogeneity of the Slime-EPS matrix composition for multi- versus single-species biofilms. Secondly, to attempt to quantify the adsorptive capacity of the Slime-EPS fragment utilizing a published dye-probing analysis protocol. Finally, to assess the capacity for chronic (7-day) micropollutant exposure to influence the composition and yield of the Slime-EPS fragment for a known, biofilm producing Pseudomonas species. Single-species biofilms exhibited a more consistent Slime-EPS composition in terms of their protein: carbohydrate ratio. Dye-probing analysis efforts indicated the capacity for toluidine blue dye to exhibit altered spectral absorbance as a result of increased dimerization – which was found to be influenced by both the introduction of the Slime-EPS itself and increasing concentrations of NaCl. Increasing concentrations of TB dye was shown to induce hypsochromic (blue-) spectral shifts. Ciprofloxacin was found to significantly reduce the biofilm Slime-EPS yield (p < 0.05) following 7 days of continuous exposure, whereas exposure to diclofenac for the same interval had no significant effect on Slime-EPS yield. Neither ciprofloxacin nor diclofenac had a significant effect on the Slime-EPS protein: carbohydrate ratio following 7 days of exposure.