Screening, isolation and characterisation of antimicrobial/antifungal peptides produced by lactic acid bacteria isolated from wine

[摘要] ENGLISH ABSTRACT: Winemaking is an age-old tradition that dates back to as early as 6000 BC. In ourmodern era there are several insects and microorganisms that pose a threat to thegrapevine, the environment and the final wine product. Farmers and winemakers arebecoming aware of the threat and the fight against disease, spoilage and/orpathogenic microorganisms is on the rise. Currently, the natural environment is beingaltered through rural developments, pollution and disaster, which in turn isresponsible for altering the natural micro flora. The result is a harsh battle betweenman and microorganism. The weapon used often against microorganisms is chemicalpreservatives, such as sulphur dioxide. These chemical preservatives change thenutritional value, quality and wholesomeness of the wine. Chemical preservativessuppress the quality of the wine with a reduction in wine consumption by theconsumers.Until the 18th century, wine was regarded as a safe drink and prescribed bydoctors. In the zo century alcohol consumption became the focus point of somehealth campaigners. Medical science restored the good name of wine in the 1990swhen it came to light that moderate red wine consumption may aid in preventingheart disease and assist in stress management. The only drawback that lowersconsumption levels is the use of chemical preservatives.It is of utmost importance to place the focus on health issues and the developmentof natural preservation methods that are environmentally friendly and contributes tothe overall wholesomeness of the wine. Due to these demands, the scientificcommunity placed the focus of research projects on the development andenhancement of biopreservation methods, in order to minimise chemical preservationuse.One of the most promising biocontrol agents is bacteriocins. These proteinaceousmolecules produced by various lactic acid bacteria exert antimicrobial activity towardsclosely related organism. Research has shown that bacteriocins may aid in theprevention of wine-spoilage and enhance natural preservation techniques.Most of the research on biopreservation in food and beverages has beenperformed on the bacteriocins of LAB. No evidence could be found that indicatedbacteriocin 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 SouthAfrican wine industry.The main objective of this study was to screen wine isolated LAB for theproduction of antimicrobial and/or antifungal compounds. This was followed by theisolation and characterisation of the produced bacteriocins. This study forms part of agreater project that focuses on wine preservation, under the auspices of the Institutefor Wine Biotechnology.The research results in this study indicated the production of bacteriocins bywine isolated LAB of South African origin. It was found that numerous isolatesexerted antimicrobial activity towards other wine associated LAB. The mostpredominant species that gave the highest activity was Lactobacillus brevis andLactobacillus paracasei. Experimental results indicated that the bacteriocinsproduced 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 wineenvironment. The antimicrobial activity was lost after treatment with proteolyticenzymes, such as proteinase K and lysozyme. The size, production and growthkinetic curves of the bacteriocins under investigation showed similar results that arecomparable to other findings in the literature. Antifungal activity was detected againstBotryfis 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 LABisolated from the South African wine industry. The results indicate the suitability ofthese bacteriocins as possible biopreservatives in the wine environment. Theproposed 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 thewinemaking process.

[发布机构] Stellenbosch University