Thesis (MSc)--Stellenbosch University, 2003. / Full text to be digitised and attached to bibliographic record. / 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. / AFRIKAANSE OPSOMMING: Wynmaak is 'n eeu oue tradisie wat terugdateer tot so vroeg soos 6000 jaar v.C. In
ons moderne eeu is daar verskeie insekte en mikro-organismes wat In bedreiging vir
die wingerdstok, asook die omgewing en die finale wynproduk inhou. Boere en
wynmakers word al hoe meer bewus van hierdie bedreiging, terwyl die stryd teen
siektes, bederf en/of patogene mikro-organismes ook aan die toeneem is. Tans word
die natuurlike omgewing deur landelike ontwikkeling, besoedeling en natuurlike
rampe verander, wat op sy beurt weer verantwoordelik is vir die verandering van
mikroflora. Die gevolg is 'n harde stryd tussen die mens en mikro-organismes. Die
wapen wat gereeld ingespan word in die stryd teen mikro-organismes, is chemiese
preserveermiddels, soos swaweidioksied. Hierdie chemiese preserveermiddels
verander die voedingswaarde, kwaliteit en die voedsaamheid van die wyn. Dit
onderdruk ook die gehalte van wyn, wat meebring dat minder wyn deur die verbruiker
gedrink word.
Tot en met die agtiende eeu is wyn deur dokters as 'n veilige drankie voorgeskryf.
In die twintigste eeu het alkoholverbruik die fokuspunt van gesondheidskamvegters
geword. In die 1990's het die mediese wetenskap wyn se goeie naam in ere herstel
toe dit aan die lig gekom het dat In matige verbruik van rooiwyn moontlik hartsiektes
kan voorkom en help om stres te beheer. Die enigste nadelige faktor wat
verbruikersvlakke verlaag, is die gebruik van chemiese preserveermiddels.
Dit is uiters noodsaaklik om die fokus op gesondheidskwessies te plaas en die
ontwikkeling van natuurlike preserveermetodes wat omgewingsvriendelik is en tot die
algehele voedsaamheid van wyn bydra. As gevolg van hierdie eise het
wetenskaplikes die fokus geplaas op navorsingsprojekte vir die ontwikkeling en
verbetering van biopreserveringsmetodes met die doelom die gebruik van chemiese
preserveermiddels te verminder.
Een van die belowendste biokontrolemiddels is bakteriosiene. Hierdie
proteïenagtige molekule word deur verskeie melksuurbakterieë vervaardig en oefen
anti-mikrobiese aktiwiteit teenoor nabyverwante organismes uit. Navorsing het
getoon dat bakteriosiene moontlik kan help in die voorkoming van wynbederf en
natuurlike preserveertegnieke kan verbeter.
Die meeste van die navorsing op biopreservering in voedsel en drank is op die
bakteriosiene van melksuurbakterieë uitgevoer. Geen bewys kon gevind word in Suid
Afrika wat bakteriosienproduksie deur wyn-geïsoleerde melksuurbakterieë aangedui
het nie. Hierdie studie is daarom baie belangrik en word as baanbreker werk vir die
Suid Afrikaanse wynbedryf beskou.
Die hoofdoel van hierdie studie was om wyn-geïsoleerde melksuurbakterieë vir die
produksie van anti-mikrobiese en/of anti-fungiese substanse te toets. Dit is gevolg
deur die isolasie en karakterisering van die geproduseerde bakteriosiene. Hierdie
studie maak deel uit van 'n groter projek wat fokus op wynpreservering en wat onder
leiding van die Instituut van Wynbiotegnologie uitgevoer word.
Navorsingsresultate van hierdie studie dui op die produksie van bakteriosiene deur
wyn-geïsoleerde melksuurbakterieë van Suid Afrikaanse oorsrong.
Daar is gevind dat verskeie isolate anti-mikrobiese aktiwiteit teenoor ander
wynverwante malksuurbakterieë uitgeoefen het. Die oorheersende spesie wat die
hoogste aktiwiteit getoon het, was Lactobacillus brevis en Lactobacillus paracasei.
Eksperimentele uitslae dui daarop dat die bakteriosiene wat deur hierdie twee
spesies geproduseer word, termostabiel en aktief is oor 'n wye pH reeks, insluitende
die temperature en pH-waardes wat in die Suid Afrikaanse wynomgewing voorkom.
Die anti-mikrobiese aktiwiteit het verlore gegaan na behandeling met proteolitiese
ensieme soos proteïnase K. Die groote, produksie en groeikinetika kurwes van die
bakteriosiene wat ondersoek is, toon vergelykbare resultate met ander bevindings in
die literatuur. Anti-fungiese aktiwiteit is opgemerk teen Botrytis cinerea, wat beperkte
inhiberende aktiwiteit ten opsigte van spoorontkieming aangedui het, maar geen
effek op hifegroei gehad nie.
Hierdie studie verskaf nuwe inligting aangaande bakteriosienproduksie deur
melksuurbakterieë wat van die Suid Afrikaanse wynomgewing geïsoleer is. Die
resultate dui op die geskiktheid van hierdie bakteriosiene as moontlike
biopreserveermiddels in die wynbedryf. Die voorgestelde resultate deur hierdie studie
verkry sal help in die ontwikkeling van bakteriosien produserende, spesifiek
vervaardigse wyngis of melksuurbakterieë, wat in die toekoms 'n baie belangrike rol
in die wynmaakproses sal speel.
Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53582 |
Date | 03 1900 |
Creators | Morgan, Joanne |
Contributors | Du Toit, M., Pretorius, I. S., Vivier, M. A., Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology. |
Publisher | Stellenbosch : Stellenbosch University |
Source Sets | South African National ETD Portal |
Language | en_ZA |
Detected Language | Unknown |
Type | Thesis |
Format | 82 pages : illustrations |
Rights | Stellenbosch University |
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