The Department of Microbiology proudly delivered four new doctoral graduates who received their degrees during the recent December 2014 and March 2015 graduation ceremonies.
Dr Eunice Nonhlanhla Zwane
Dissertation title: Production, characterisation and application of a recombinant ferulic acid esterase from Aspergillus tubingensis
Dissertation Summary / Tesis Opsomming
Supervisors: Prof M Viljoen-Bloom, Prof WH van Zyl, Dr K Rumbold
Dr Heinrich Kroukamp
Dissertation title: Improving the protein secretion capacity of Saccharomyces cerevisiae with strain engineering
Baker’s yeast is frequently used for the production of industrial and biopharmaceutical proteins. Improving the production and secretion of recombinant proteins has the benefit of reducing the production costs and promoting accessibility to these technologies. This also holds true for second generation biofuel production, where high levels of hydro- lytic enzymes are required to break down the complex carbohydrates in agricultural waste. The successful application of yeast strain engineering approaches was demonstrated to increase the secreted yields of several types of cellulolytic proteins, identifying potential genetic elements that promote secretion in yeast and some of the mechanisms responsible for this enhanced protein secretion were elucidated.
Promoter: Prof WH van Zyl
External Co-supervisor: Dr R den Haan
Dr Kim Trollope
Dissertation title: Engineering a fungal β-fructofuranosidase
Random and semi-rational protein engineering approaches were used to improve the Aspergillus japonicus β-fructofuranosidase enzyme for fructooligosaccharide (FOS ) synthesis from sucrose. Improved enzyme variants were identified showing enhanced FOS , production efficiency, specific activity and thermostability. The study detailed a new method to rapidly quantify FOS , using mid-infrared spectroscopy and a bioinformatics tool for in silico functional sub- classification of β-fructofuranosidases . The improved enzymes, combined with enzyme structure-function insights, will
benefit future industrial production of FOS, a health-promoting dietary supplement for humans and animals.
Supervisor: Dr H Volschenk
Co-supervisor: Prof J Görgens
Dr Du Preez van Staden
Dissertation title: In vitro and in vivo characterisation of amyloliquecidin, a novel two-component lantibiotic produced by Bacillus amyloliquefaciens
Antimicrobial resistance is one of the major problems faced by the medical industry. Two antimicrobial-producing bacteria, Bacillus clausii AD1 and Bacillus amyloliquefaciens AD2, were isolated from Fynbos soil in the Western Cape. Both strains produced lantibiotics, i.e. ribosomally synthesised cationic antimicrobial peptides, with extensive post-translational modifications. The lantibiotics were active against a number of pathogenic bacteria. Amyloliquecidin, produced by strain AD2, is a novel two-peptide lantibiotic active against Staphylococcus aureus. The peptide was extremely effective in the treatment of skin infections and stimulated wound healing. The two operons encoding the production and secretion of the lantibiotics were sequenced and annotated.
Supervisor: Prof LMT Dicks
Co-supervisor: Dr SM Deane
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