Browsing by Author "Morgan, Joanne"
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- ItemScreening, isolation and characterisation of antimicrobial/antifungal peptides produced by lactic acid bacteria isolated from wine(Stellenbosch : Stellenbosch University, 2003-03) Morgan, Joanne; Du Toit, M.; Pretorius, I. S.; Vivier, Melane A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology.ENGLISH ABSTRACT: Winemaking is an age-old tradition that dates back to as early as 6000 BC. In our modern era there are several insects and microorganisms that pose a threat to the grapevine, the environment and the final wine product. Farmers and winemakers are becoming aware of the threat and the fight against disease, spoilage and/or pathogenic microorganisms is on the rise. Currently, the natural environment is being altered through rural developments, pollution and disaster, which in turn is responsible for altering the natural micro flora. The result is a harsh battle between man and microorganism. The weapon used often against microorganisms is chemical preservatives, such as sulphur dioxide. These chemical preservatives change the nutritional value, quality and wholesomeness of the wine. Chemical preservatives suppress the quality of the wine with a reduction in wine consumption by the consumers. Until the 18th century, wine was regarded as a safe drink and prescribed by doctors. In the zo" century alcohol consumption became the focus point of some health campaigners. Medical science restored the good name of wine in the 1990s when it came to light that moderate red wine consumption may aid in preventing heart disease and assist in stress management. The only drawback that lowers consumption levels is the use of chemical preservatives. It is of utmost importance to place the focus on health issues and the development of natural preservation methods that are environmentally friendly and contributes to the overall wholesomeness of the wine. Due to these demands, the scientific community placed the focus of research projects on the development and enhancement of biopreservation methods, in order to minimise chemical preservation use. One of the most promising biocontrol agents is bacteriocins. These proteinaceous molecules produced by various lactic acid bacteria exert antimicrobial activity towards closely related organism. Research has shown that bacteriocins may aid in the prevention of wine-spoilage and enhance natural preservation techniques. Most of the research on biopreservation in food and beverages has been performed on the bacteriocins of LAB. No evidence could be found that indicated bacteriocin production by wine isolated LAB in South Africa. This study is therefore, of utmost importance and is considered to be novel pioneering work for the South African wine industry. The main objective of this study was to screen wine isolated LAB for the production of antimicrobial and/or antifungal compounds. This was followed by the isolation and characterisation of the produced bacteriocins. This study forms part of a greater project that focuses on wine preservation, under the auspices of the Institute for Wine Biotechnology.The research results in this study indicated the production of bacteriocins by wine isolated LAB of South African origin. It was found that numerous isolates exerted antimicrobial activity towards other wine associated LAB. The most predominant species that gave the highest activity was Lactobacillus brevis and Lactobacillus paracasei. Experimental results indicated that the bacteriocins produced by these two species were thermo-stable and active over a wide pH range, including the temperatures and pH values that reign in the South African wine environment. The antimicrobial activity was lost after treatment with proteolytic enzymes, such as proteinase K and lysozyme. The size, production and growth kinetic curves of the bacteriocins under investigation showed similar results that are comparable to other findings in the literature. Antifungal activity was detected against Botryfis cinerea that indicated limited inhibitory activity towards spore germination, but had no effect on hyphal growth. This study provides novel information regarding bacteriocin production by LAB isolated from the South African wine industry. The results indicate the suitability of these bacteriocins as possible biopreservatives in the wine environment. The proposed results obtained in this study will aid in the development of bacteriocinproducing, tailored made wine yeast or LAB that may in future, play vital roles in the winemaking process.