Browsing by Author "Botes, DP"

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    Cloning and expression of a chimeric protease inhibitor encoding gene in Escherichia coli and Pichia pastoris
    (1996) Matsebula, Aaron Mfanuzile; Botes, DP; Klump, HH; Maeder, Dennis
    Squash family protease inhibitors are small peptides of 27-32 residues, hence they are ideal subjects for structure-function studies. Their small size is within the reach of peptide chemical synthesis, which enables one to produce enough peptide material for experimental purposes within a reasonable time frame.
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    The enzymatic release of glycosidically-bound terpenes in must
    (1989) Strauss, Lindie Helene; Botes, DP
    Flavour in wines is perhaps the most important factor affecting wine quality, with monoterpenoids being among the compounds contributing to flavour. In grapes there exists glycosidically-bound forms of these monoterpenes, representing a latent source of aroma. This project is a study on the ability of different enzymes to release these monoterpenes in Muscat d'Alexandrie and Weisser Riesling grapes. Different commercial enzyme preparations were characterised with respect to their catalytic properties and fractionated by ion exchange chromatography in the most active fractions. Amongst those commercial preparations tested, Rohapect C was found to be the most effective at conditions prevalent during wine making. These purified fractions were added to the above mentioned grapes to determine their effect on the release of different monoterpenes. Even though the enzymes were active on synthetic substrates, limited release of terpenes from must could be detected. Possible causes for this apparent inability to release monoterpenes were investigated. Product inhibition due to the presence of high concentrations of glucose in the must appeared to be the main cause of limited enzyme activity. In an attempt to overcome this problem, glucose in the above mentioned cultivars was oxidised to gluconic acid by glucose oxidase, prior to attempting monoterpene release by Rohapect C. Although no marked increase in the release of total terpenes occured, a significant increase in the concentrations of some individual terpenes could be observed. The effect of this on wine quality remains to be ascertained.