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The purification and functional study of compounds produced by Escherichia coli BP that induce and Inhibit sulphate reducing bacteria growth

Student thesis: Doctoral Thesis

The induction and inhibition of sulphate reducing bacteria (SRB) growth is of academic and biotechnological interests due to their involvement in corrosion, hydrocarbon degradation and reservoir souring. The purification and functional study of SRB growth enhancer (SGE) and SRB growth inhibitor (SGI) produced by Escherichia coli BP is reported in this research. The SGE can be used as a supplement in the media for rapid SRB detection while the SGI can be used for the prevention of biocorrosion mainly induced by SRB.

The optimum growth conditions for highest SGE production were determined. The enhancer and inhibitor were purified using ion exchange and size exclusion chromatography. SRB cultures in the presence of SGE showed two order of magnitude higher growth than untreated SRB while with SGI they showed growth with two order of magnitude less.

Scanning electron microscopy (SEM), atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM) were used to study the effects of the enhancer and inhibitor on SRB growth. The SRB treated with the enhancer had growth enhancement while the inhibitor caused changes of SRB morphology and revealed the bactericidal effects on SRB growth.

The structural analysis of purified SGE and SGI were carried out using nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption ionisation–time of flight (MALDI-TOF) spectrometry. The NMR spectra of SGI and SGE were assigned to methylene, methine, alkynes, ketones, esters, aromatics and amides functional groups.

The MALDI-TOF spectra in linear mode showed the compounds to be an oligomeric series with repeat ~ 213 m/z unit between each of the peaks. The data revealed that the molecular mass of SGE is around 1700 Da while that of SGI is estimated as 2400 Da.
Original languageEnglish
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Award dateJun 2016

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