55 research outputs found
Endophytic Diversity in Vitis vinifera with Different Vineyard Managements and Vitis sylvestris Populations from Northern Italy: A Comparative Study of Culture-Dependent and Amplicon Sequencing Methods
No full textThis study aimed to investigate the endophytic microbial populations associated
with wild and domesticated grapevines using both culture-based and culture-independent
methods. Through culture-based methods, 148 endophytes were identified. The dominant
fungal species included Aureobasidium pullulans, Alternaria alternata, and Cladosporium allicinum,
while predominant bacterial species were Ralstonia pikettii, Nocardia niigatensis, and
Sphingomonas echinoides. Culture-independent methods employed metagenomic techniques
to explore microbial biodiversity, focusing on targeted amplification of bacterial 16S rRNA
as well as fungal ITS and 26S rRNA gene regions. The main bacterial species identified
included Halomonas sp., Sphingomonas sp. and Massilia sp., whereas the fungal population
was dominated by Cladosporium sp., Malassezia sp. and Mucor sp. The findings revealed
that vineyard management practices did not lead to statistically significant variations in
microbial communities. The consistent presence of these genera across all samples suggests
that they are stable components of the grapevine endophytic microbiota, remaining
relatively unaffected by external environmental factors
Heterologous production of family 5 fungal endo-1,4-B-mannanases in Saccharomyces cerevisiae
No full textDissertation (PhD)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: Mannan polysaccharides occur in the hemicellulose fraction of plant cell walls, either as
structural polymers or as reserve carbohydrates. They are found predominantly in the
seeds of leguminous plants in the form of galactomannan, and in softwoods as
galactoglucomannan. Endo-I,4-I3-mannanases hydrolyze mannan polysaccharides to
oligosaccharides of various lengths. These enzymes are secreted as single catalytic
modules or as part of multi-modular proteins by fungi, bacteria, plants and animals. For
example, the l3-mannanase of Aspergillus aculeatus, designated Aa-Man5A, is secreted
as a single catalytic module, whereas that of Trichoderma reesei, designated Tr-Man5A,
contains a l3-mannanase catalytic module linked to a cellulose-binding module by a Pro-
Ser-Thr-rich linker.
Heterologous gene expression in yeast provides the opportunity to produce individual
hydrolytic enzymes in a host expression system devoid of related activities.
Saccharomyces cerevisiae has a well-developed expression system and has frequently
been used as a model organism for heterologous gene expression. A number of
autoselection systems have been devised so that recombinant S. cerevisiae strains can be
cultivated in any medium of choice without exerting selective pressure. An autoselection
system based on defective chromosomal ura3 andfurl genes involved in the pyrimidine
biosynthesis pathway of S. cerevisiae, and complementation of the ura3 gene with a
multicopy plasmid-borne URA3 gene, were used in this study.
The man1 of A. aculeatus gene encoding Aa-Man5A was cloned and expressed in
autoselective S. cerevisiae under the regulation of the alcohol dehydrogenase (ADH2PT)
and the phosphoglycerate kinase (PGK1PT) promoter and terminator sequences.
Expression of man1 under both promoters resulted in high production levels of Aa-
Man5A. The production levels were significantly higher than the levels of endo-l,4-13-
mannanases produced by heterologous expression in Escherichia coli, and were
comparable to the production levels of enzymes produced in Pichia pastoris, which
presumably has a higher secretion capacity than S. cerevisiae. The recombinant yeast strain expressing man1 under the regulation of the PGK1p promoter displayed stunted
biomass formation during the logarithmic phase, which was relieved when the native f3-
mannanase secretion signal was replaced with the yeast MFuis secretion signal. The
recombinant Aa-Man5A displayed biochemical properties similar to those of the native
Aa-Man5A. The recombinant enzyme hydrolyzed unsubstituted mannan to
predominantly mannose, mannobiose, and mannotriose.
The expression of the man1 and man1 ácbd gene constructs of T reesei in S. cerevisiae
fur 1::LEU2 strains under the regulation of the PGK1 PT promoter and terminator resulted
in the production and secretion of Tr-Man5A and Tr-Man5A~CBD (lacking the cellulose
binding module), respectively. However, the production levels of both proteins were
approximately I5-fold lower than the production levels of Aa-Man5A. These levels did
not improve after replacement of the native secretion signal with the MFuis secretion
signal. Interestingly, reducing the cultivation temperature from 30°C to 20°C led to a
five-fold increase in the secreted levels of Tr-Man5A, but a three-fold decrease in the
production of Aa-Man5A.
A preliminary investigation was performed to evaluate the possibility of using the
recombinant Aa-Man5A in the processing of instant coffee. Arabica coffee extracts
treated with Aa-Man5A displayed low viscosity in comparison to the untreated extract
and showed better retention of volatile/aromatic compounds than the autoclaved extract.
The results indicated that Aa-Man5A is capable of hydrolyzing coffee galactomannan
and can be used for processing instant coffee.AFRIKAANSE OPSOMMING: Mannaanpolisakkariede kom in die hemisellulose fraksie van plantselwande as
strukturele polimere of reserwe koolstofbron voor. Mannaan word hoofsaaklik in die sade
van peulplante, III die vorm van galaktomannaan, en III sagtehout as
galaktoglucomannaan aangetref. Endo-I,4-j3-mannanase kan mannaanpolisakkariede na
oligosakkariede van verskillende lengtes afbreek. Hierdie ensieme word deur fungi,
bakterieë, plante en diere as enkele katalitiese modules of as deel van multi-modulêre
proteïene uitgeskei. Die j3-mannanase (Aa-Man5A) van Aspergillus aculeatus is
byvoorbeeld 'n enkele katalitiese module, maar die j3-mannanase (Tr-Man5A) van
Trichoderma reesei bestaan uit 'n j3-mannanase katalitiese module gekoppel aan 'n
sellulose-bindingsmodule deur middel van 'n Pro-Ser- Thr-ryke koppelstuk.
Heteroloë geenuitdrukking in gIS bied die geleentheid om individuele hydrolitiese
ensieme in 'n gasheer uitdrukkingsisteem sonder verwante aktiwiteite te produseer.
Saccharomyces cerevisiae het 'n goed ontwikkelde uitdrukkingsisteem en word as model
organisme vir heteroloë geenuitdrukking gebruik. 'n Aantal outoseleksiesisteme is
ontwikkel, waardeur rekombinante S. cerevisiae-tese in enige medium sonder selektiewe
druk gekweek kan word. 'n Outoseleksiesisteem, gebaseer op defektiewe chromosomale
ura3 en furl gene wat vir ensieme in die pirimidien biosinteseweg kodeer, en
komplementasie van die ura3-geen met die wilde-tipe URA3-geen wat op In multikopie
plasmied teenwoordig is, is vir hierdie studie gebruik.
Die manl-geen, wat vir die Aa-Man5A j3-mannanase van A. aculeatus kodeer, is
gekloneer en in outoselektiewe S. cerevisiae onder die regulering van die
alkoholdehidrogenase 2 (ADH2PT) en fosfogliseraatkinase 1 (POKl PT) promotor- en
termineerderopeenvolgings uitgedruk. Uitdrukking van die manl-geen onder albei
promotors het hoë produksievlakke van Aa-Man5A gelewer. Die produksievlakke was
aansienlik hoër as die endo-I,4-j3-mannanase-vlakke wat deur heteroloë geenuitdrukking
in Escherichia coli geproduseer was, en kon vergelyk word met die produksievlakke van ensieme in Pichia pastoris. P. pastoris is veronderstel om In hoër sekresiekapasiteit as
S. cerevisiae te hê. Die rekombinante gisras wat die manl-geen onder beheer van die
PGKl p promotor uitgedruk het, se biomassavorming was belemmer gedurende die laat
logaritmiese fase. Die belemmering is opgehef nadat die natuurlike sekresiesein van
13-mannanasemet die MFais sekresiesein vervang is. Die rekombinante Aa-ManSA het
soortgelyke biochemiese eienskappe as die natuurlike Aa-ManSA getoon. Die
rekombinante ensiem het onvertakte mannaan tot hoofsaaklik mannose, mannobiose en
mannotriose gehidroliseer.
Die uitdrukking van die manl- en manl Licbd-geenkonstrukte van T. reesei in
S. cerevisiae furl::LEU2-rasse onder regulering van die PGKlPT promotor en
termineerder het tot die produksie en sekresie van onderskeidelik die Tr-ManSA en
Tr-ManSAilCBD (sonder die sellulose-bindingsdomein) ensieme gelei. Die
produksievlakke van beide proteïene was egter ongeveer IS-voudig laer as die vlakke van
Aa-ManSA. Hierdie vlakke het egter nie verbeter nadat die natuurlike sekresiesein met
die MFais sekresiesein vervang is nie. Interessant is die feit dat 'n afname in
opkwekingstemperatuur vanaf 30°C tot 20°C tot 'n vyf-voudige toename m
sekresievlakke van die Tr-ManSA gelei het, maar tot 'n drie-voudige afname in die
produksie van Aa-ManSA.
'n Voorlopige ondersoek na die moontlike gebruik van rekombinante Aa-ManSA in
kitskoffieprosessering is ondersoek.. Arabica koffie-ekstrak wat met Aa-ManSA
behandel is, het 'n laer viskositeit in vergelyking met onbehandelde ekstrak getoon, asook
beter behoud van vlugtige/aromatiese verbindings in vergelyking met geoutoklaveerde
ekstrak. Hierdie resultate toon dat Aa-ManSA in staat is om koffee galaktomannaan te
hidroliseer en dat dit vir die prosessering van kitskoffie gebruik kan word.Doctora
Comparative analysis of fermentative yeasts during spontaneous fermentation of grapes from different management systems
No full textThesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The microorganisms associated with grape berry surface can be influenced by numerous factors such as agronomic parameters. Hence, the focus of this study was comparison between three agronomic farming systems to evaluate their impact on yeast diversity. In addition, the dynamics of the yeast population throughout wine alcoholic fermentation were monitored. Three vineyards (conventional, biodynamic and integrated) were chosen and the experiment was carried out during the 2012 and 2013 vintages. A total of 600 yeast isolates including Saccharomyces and non-Saccharomyces were obtained from grape must and during different stages of fermentation including beginning, middle and end of alcoholic fermentation, from all three vineyards. Yeast species diversity in grape must and their population dynamics were evaluated by cultivating the yeasts in nutrient media and using “Polymerase Chain Reaction and sequence analysis of the ITS1-5.8S rRNA-ITS2 region. Eight, four and one species were detected from biodynamic, conventional and integrated must in 2012 vintage whereas, 2013 vintage displayed a higher diversity and 12, 11 and 9 different species were identified from biodynamic, conventional and integrated vineyard, respectively. Aureobasidium pullulans was the most frequent isolate in all three vineyards whereas Saccharomyces cerevisiae was below detection level in grape must and was only isolated in low frequencies in biodynamic must (3% of the total population) in both vintages. In general, the overlap of common yeast isolates (e.g. M. pulcherrima and H. uvarum) was observed in the musts obtained from different vineyards although unique minor species could be isolated and clearly demonstrated the distinction between the three vineyards. Moreover, biodynamic must displayed a higher degree of diversity in both 2012 and 2013 compared to the conventional and integrated vineyards. The beginning of all spontaneous fermentations was dominated by non-Saccharomyces yeast species (e.g. H. uvarum, C. zemplinina), as the fermentation proceeded, the population of non-Saccharomyces species were gradually decreased and strongly fermentative yeast S. cerevisiae dominated and completed the fermentations. The dynamics of S. cerevisiae strains was also evaluated during different stages of fermentation (beginning, middle and end), using interdelta PCR methods. A high diversity (10-18 strains per fermentation) and the sequential substitution of S. cerevisiae strains were observed throughout spontaneous fermentations. In addition, integrated vineyard displayed the highest S. cerevisiae strains compared to biodynamic and conventional vineyard.AFRIKAANSE OPSOMMING: Die mikro-organismes wat met die oppervlak van druiwe bessies geassosieer word kan deur veskeie agronomiese faktore beїnvloed word. Gevolglik was die focus van die studie om ‘n vergelyking tussen die impak van drie verksillende boerdery sisteme op die invloed op gis diversiteit te bepaal. Die dinamiek van gis populasies tydens alkoholiese fermentasie is bykomstig bestudeer. Drie verskillende wingerde (konvesioneel, biodinamies en geïntegreerd) is gebruik vir die studie tydens die 2012 en 2013 oesjare. In total is 600 gis isolate, insluitend Saccharomyces en nie-Saccharomyces giste, verky van druiwe mos tydens verkillende fases van die fermentasie proses (begin, middle en einde) vir al drie wingerde. Die diversiteit en populasie dinamika van gis spesies in die druiwe mos is geëvalueer deur die giste in verskillendde media op te groei en ook deur die gebruik van die “polymerase ketting reaksie” (PKR) en DNS volgorde bepaling van die ITS1-5.8S rRNA-ITS2 gebied. Tydens die 2012 oesjaar is agt, vier en een afsonderlike spesies geїsoleer, in vergelyking met die 12, 11 en 9 verskillende spesies wat tydens 2013 geidentifiseer is is uit die biodinamiese, konsensionele en geïntegreerde onderskeidelik. Aureobasidium pullulans is teen die hoogste frekwensie geїsoleer in al drie wingerde, terwyl Saccharomyces cerevisiae onder die deteksie limiet was in druiwe mos en ook slegs in lae getalle in die biodinamiese mos (3% van die totale populasie) in beide oesjare. Oor die algemeen is ‘n oorvleuling tussen verwante spesies (bv. M. pulcherrima en H. uvarum) waargeneem en die mos vanaf verskillende wingerde, terwyl meer geringe spesies deurgans geїsoleer kon word en duidelik ‘n verkill tussen die drie wingerde uitgewys het. Druiwe mos uit die biodinamiese wingerd het verder ‘n hoёr graad van diversiteit en beide 2012 en 2013 vertoon as beide die konvesnionele en geïntegreerde wingerde. Die begin van alle spontane fermentasies was gedomineer deur die populasie van nie-Saccharomyces gis spesies (bv. H. uvarum, C. zemplinina), wat geleidelik afgeneem het met die verloop van die fermentasie. Die populasie van die sterk fermentatiewe, S. cerevisiae, het toegeneem tydens fermentasie en die fermentasie afgehanel as dominante gis. Die dinamika van S. cerevisiae rasse is ook geëvalueer tydens die verskillende fases van fermentasie (begin, middle en einde) deur gebruik te maak van interdelta PKR metodes. ‘n Hoё diversiteit (10-18 rasse per fermentasie) en die opeenvolgende verplasing van S. cerevisiae rasse was waargeneem deur die verloop van spontane fermentasies. Daarbenewens het die geïntegreerde wingerd die grootste getal S. cerevisiae rasse in vergelyking met die biodinamiese en konvensionele wingerde opgelewer.Master
Bacterial diversity of Cabernet Sauvignon must from different locations and the dynamics during wine fermentation
No full textThesis (MScAgric)--Stellenbosch University, 2022.ENGLISH ABSTRACT: Wine grapes harbour a microbiota that drives wine fermentations that may contribute to the
chemical fingerprint of finished wines. The bacterial communities on grapes, in particular lactic
acid bacteria (LAB) conduct malolactic fermentation (MLF), which modifies the acidity, flavour and
microbial stability of wine. This study aimed to investigate the bacterial diversity on Vitis vinifera
L. cv Cabernet Sauvignon in three vineyards (VIN-A, VIN-B and VIN-C), situated in different areas
of the Stellenbosch wine district during 2019 and 2020 vintages. The Automated Ribosomal
Intergenic Spacer Analysis (ARISA) was used to evaluate the community fingerprint of grape
must. Bacterial population dynamics and diversity were determined in grape must and throughout
the wine fermentation by cultivating bacteria on nutrient media and using Polymerase Chain
Reaction and sequence analysis of the 16S region. Followed by the characterisation of a selection
of Lactiplantibacillus plantarum and Oenococcus oeni isolates from the 2019 and 2020 vintages,
which were subjected to Random Amplified Polymorphic DNA (RAPD) typing to generate genetic
profiles, which were compared to determine their recurrence in the various vineyards.
Chemical composition (pH, malic acid and sugar) of the grape must from each vineyard were
different for both vintages. The fermentations differed between the vineyards, the wines from VIN-
A was able to complete the MLF in 2019, while other vineyards presented stuck MLF.
Using ARISA, 117 and 116 peaks were detected in 2019 and 2020, respectively. Each peak was
considered as an operational taxonomic unit (OTU). The data showed some overlap of the OTUs
in grape must from different vineyards. Thirteen bacterial OTUs in 2019 and 8 peaks in 2020 were
detected in all three vineyards, whereas the majority of the OTUs were vineyard specific. Analysis
of similarities (ANOSIM) of the OTU data showed notable differences in the bacterial communities
between vintages.
The viable counts of the grape must differed between the vintages. In 2019, the total bacterial
population density in grape must ranged between 103 and 105 colony forming units per millilitres
(CFU/mL), while in 2020, the bacterial population density ranged between 103 and 104 CFU/mL.
A total of 360 bacterial isolates including both LAB and acetic acid bacteria (AAB) were obtained
from grape must and different stages of fermentation from all vineyards during both vintages. The
bacterial diversity differed between the vineyards and over the vintages. Five bacterial species
were detected in grape must from VIN-B and VIN-C and 3 species in VIN-A in 2019, whereas
2020 presented higher bacterial diversity and 6, 11 and 6 different species were identified in VIN-
A, VIN-B and VIN-C respectively. L. plantarum was found in grape must from all vineyards,
accounting for more than 50% of the total population. O. oeni was detected in grape must of both
2019 and 2020 vintages from VIN-B and VIN-C, where it accounted for 4% of the total population
in 2019. In general, the overlap of common species such as Apilactobacillus kunkeei and
Acetobacter malorum was observed in wine from different vineyards. Minor unique species were
isolated and clearly differed between the three vineyards. In addition, L. plantarum ISP20_9 and
O. oeni ISO20_1 were the only isolates that were recurring in both 2019 and 2020 vintages. The
L. plantarum and O. oeni strains showed different patterns of malic acid degradation within 7
days, indicating strain differences.AFRIKAANSE OPSOMMING: Wyndruiwe huisves mikrobes wat die alkoholiese fermentasie dryf en bydra tot die chemiese
profiel van die finale wyne. Die bakteriese gemeenskap op druiwe, veral melksuurbakterieë (MSB)
voer appelmelksuurgisting (AMG) uit wat die suurheid, geur en mikrobiese stabiliteit van wyn kan
modifiseer. Die doel van hierdie studie was om die bakteriese diversiteit op Vitis vinifera L. cv
Cabernet Sauvignon, in drie wingerde (VIN-A, VIN-B and VIN-C) wat in verskillende areas van
die Stellenbosch Wyndistrik geleë is, te ondersoek tydens die 2019 and 2020 oesjare.
Outomatiese Ribosomale Intergeniese Spasieerder Analise (ORISA) was gebruik om die
vingerafdruk van die mikrobiese gemeenskap van die druiwemos te genereer. Die bakteriese
populasie dinamika en diversiteit van druiwemos en tydens fermentasie was ondersoek, deur die
kultivering van bakterieë op voedingsmedia en die gebruik van die Polimerase kettingreaksie
(PKR) in kombinasie met volgorde analise van die 16S streek. Dit was opgevolg deur die
karakterisering van ‘n seleksie van Lactiplantibacillus plantarum and Oenococcus oeni isolate van
2019 en 2020 deur gebruik te maak Ewekansig Geamplifiseerde Polimorfiese DNA (EGPD) om
die genetiese profiele op rasvlak te onderskei. Hierdie profiele was gebruik om te bepaal watter
rasse herhaaldelik in die verskeie wingerde voorgekom het.
Die chemiese samestelling (pH, appelsuur en suiker) van die druiwemos van elke kelder het
verskil vir beide oesjare. Die fermentasies het verskil tussen wingerde en die wyne van VIN-A
kon AMG suksesvol in 2019, maar die wyne van die ander wingerde kon nie.
Een honderd en sewentien en 116 pieke kon respektiewelik in 2019 en 2020, onderskei word
deur ORISA te gebruik. Elke piek was as ‘n operasionele taksonomiese eenheid (OTE) beskou.
Die data het gewys dat daar oorvleueling tussen die OTEs van die druiwemos van die verskillende
wingerde was. Dertien bakteriese OTEs in 2019 en 8 pieke in 2020 was waargeneem in al drie
wingerde, maar die meerderheid van die OTEs was wingerd spesifiek. Ontleding van
ooreenkomste van die OTE data het gewys dat daar noemenswaardige verskille in die bakteriese
gemeenskappe tussen oesjare was.
Die lewensvatbare tellings van die bakterieë in die druiwemos het verskil tussen die oesjare. In
2019, het die totale bakteriese populasie gewissel tussen 103 and 105 kolonievormende eenhede
per milliliter (KVE/mL), terwyl dit in 2020, gevarieer het tussen 103 and 104 KVE/mL. Drie honderd
en dertig bakteriese isolate, insluitende MSB en asynsuurbakterieë (ASB), was uit druiwemos en
tydens die verskillende stadiums van fermentasie geïsoleer van al die wingerde en oor beide
oesjare. Die bakteriese diversiteit het verskil tussen die wingerde en tussen die oesjare. Vyf
bakteriese spesies was waargeneem in druiwemos VIN-B en VIN-C, maar slegs 3 spesies in
druiwemos van VIN-A in 2019. In 2020, was meer bakteriese diversiteit waargeneem en 6, 11 en
6 verskillende spesies was geïdentifiseer in druiwemos van VIN-A, VIN-B en VIN-C, respektiewelik. L. plantarum was teenwoordig in druiwemos van al die wingerde en het bygedra
tot 50% van die totale populasie. O. oeni was teenwoordig in druiwemos van VIN-B en VIN-C in
2019 en 2020, waar dit 4% van die totale populasie in 2019 verteenwoordig het. Die oorvleueling
van gemeenskaplike spesies soos Apilactobacillus kunkeei en Acetobacter malorum was
waargeneem in wyne van die verskillende wingerde. Unieke spesies wat teen lae persentasies
voorgekom het, het ook duidelik verskil tussen die drie wingerde. L. plantarum ISP20_9 en O.
oeni ISO20_1 was die enigste isolate wat herhalend voorgekom het gedurende die 2019 en 2020
oesjare. Die L. plantarum and O. oeni rasse het verskillende appelsuur afbraak patrone gewys,
wat ‘n aanduiding is van rasverskille.Master
Investigating the Effect of Selected Non-Saccharomyces Species on Wine Ecosystem Function and Major Volatiles
No full textNatural alcoholic fermentation is initiated by a diverse population of several non-Saccharomyces yeast species. However, most of the species progressively die off, leaving only a few strongly fermentative species, mainly Saccharomyces cerevisiae. The relative performance of each yeast species is dependent on its fermentation capacity, initial cell density, ecological interactions as well as tolerance to environmental factors. However, the fundamental rules underlying the working of the wine ecosystem are not fully understood. Here we use variation in cell density as a tool to evaluate the impact of individual non-Saccharomyces wine yeast species on fermentation kinetics and population dynamics of a multi-species yeast consortium in synthetic grape juice fermentation. Furthermore, the impact of individual species on aromatic properties of wine was investigated, using Gas Chromatography-Flame Ionization Detector. Fermentation kinetics was affected by the inoculation treatment. The results show that some non-Saccharomyces species support or inhibit the growth of other non-Saccharomyces species in the multi-species consortium. Overall, the fermentation inoculated with a high cell density of Starmerella bacillaris displayed the fastest fermentation kinetics while fermentation inoculated with Hanseniaspora vineae showed the slowest kinetics. The production of major volatiles was strongly affected by the treatments, and the aromatic signature could in some cases be linked to specific non-Saccharomyces species. In particular, Wickerhamomyces anomalus at high cell density contributed to elevated levels of 2-Phenylethan-1-ol whereas Starm. bacillaris at high cell density resulted in the high production of 2-methylpropanoic acid and 3-Hydroxybutanone. The data revealed possible direct and indirect influences of individual non-Saccharomyces species within a complex consortium, on wine chemical composition
Biochemical characterization and evaluation of the oenological attributes of Lachancea species
No full textThesis (MScAgric)--Stellenbosch University, 2017.ENGLISH SUMMARY: Previously thought to be the catalyst for spoilt wine, several non-Saccharomyces yeasts are now commercially available for winemaking. Increasing investigations into this group of microorganisms has emphasized their oenological potential in terms of their contribution to the organoleptic profile of the resulting wines. However, their sub-optimal fermentation performances, force their combined inoculation with the main wine yeast Saccharomyces cerevisiae. Among the non-Saccharomyces yeasts, Lachancea thermotolerans has been reported to bring about an overall improvement in wine acidity through the production of L-lactic acid and reduction of acetic acid as well as increased glycerol and 2-phenylethanol levels, which can impart a sweet taste and flowery aromas to wine, respectively. Its secretion of hydrolytic enzymes of oenological relevance has also been reported. Other species of the Lachancea genus (L. fermentati and L. lanzarotensis) have also been isolated from the fermentation environment, but have not received the same degree of focus as L. thermotolerans. The aim of this study was to investigate the oenological potential of these species, regarding their expression of oenologically relevant enzymes, their fermentation attributes and the expression and location of β-glucosidase during fermentation of synthetic and real grape must (Muscat d’Alexandrie).
All the Lachancea spp. illustrated β-glucosidase activity in initial plate screenings, while none exhibited protease or pectinase activities. L. thermotolerans and L. fermentati also displayed higher tolerance to ethanol and SO2 when exposed to varying concentrations of these inhibitory compounds. Higher fermentation performance was demonstrated by L. thermotolerans strains and L. fermentati, which performed much better in Muscat grape juice, and was the only Lachancea spp. to complete the fermentation in monoculture. During these fermentations, all three Lachancea spp. illustrated β-glucosidase activity, where the highest levels were expressed by a L. thermotolerans strain, Y940. Most of the enzyme activity originated from the cell walls of the yeasts, while lower levels were isolated in the intracellular region and none determined to be released into the medium. The mixed culture fermentations resulted in wine products with significantly different chemical compositions compared to the S. cerevisiae fermentation. L. thermotolerans and L. lanzarotensis mixed culture fermentations resulted in similar wines with increased production of common compounds including isoamyl alcohol, butanol and ethyl phenylacetate. L. fermentati seemingly produced wines dissimilar to the other Lachancea spp., producing levels of acetic acid perhaps flagging this species as a potential spoilage microorganism. This study provided novel information on relatively uninvestigated Lachancea spp., where their oenological potential was highlighted by the ability to express β-glucosidase enzymes during fermentations and producing wines significantly different from S.AFRIKAANS OPSOMMING: ‘n Aantal nie-Saccharomyces giste, voorheen aan gedink as die kataliste vir bederfde wyn, is nou kommersieël beskikbaar vir wynbereiding. In diepte ondersoeke na hierdie groep mikro-organisms het hul wynkundige potensiaal, in terme van hul bydra tot die organoleptiese profiel van die gevolglike wyn, beklemtoon. Alhoewel, hul sub-optimale fermentasie gedrag forseer hul gekombineerde inokulasie saam met die hoof wyn gis Saccharomyces cerevisiae. Onder die nie-Saccharomyces giste, word berig dat Lachancea thermotolerans ‘n algehele verbetering in wyn suurheid te weeg bring deur die produksie van L-melksuur en ‘n verlaging in asynsuur asook ‘n verhoging in gliserol en 2-fenieletanol vlakke, wat onderskeidelik ‘n soet smaak en blommerige aroma aan die wyn kan verleen. Die afskeiding van hidrolitiese ensieme van wynkundige belang is ook al berig. Ander spesies van die Lachancea genus (L. fermentati en L. lanzarotensis) is ook al uit fermentasie omgewings ge-isoleer, maar hul is nie so in deeglik soos L. thermotolerans bestudeer nie. Die doel van hierdie studie was om die wynkundige potensiaal van hierdie spesies te ondersoek, met betrekking tot die uitdrukking van wynkundige relevante ensieme, hul fermentasie eienskappe en die setel van β-glukosidase gedurende fermentasie in sintetiese en egte druiwe sap (Muscat d’Alexandrie).
Al die Lachancea spp. het β-glukosidase aktiwiteit getoon in die plaat siftings, maar het geen protease of pektinase aktiwiteit getoon nie. L. thermotolerans en L. fermentati het ‘n hoë toleransie vir etanol en SO2 vertoon in ‘n inhibiese sifting met verkillende konsentrasies van hierdie inhibitoriese komponente. L. thermotolerans rasse en L. fermentati het ook hoër fermentasie prestasie getoon; hierdie spesies was die enigste Lachancea spp. wat as monokulture die fermentasie voltooi het en goeie prestasie in Muscat druiwe sap getoon het. Gedurende hierdie fermentasies het al drie Lachancea spp. β-glukosidase aktiwiteit getoon, met die hoogste vlakke wat deur L. thermotolerans ras Y940 uitgedruk is. Meeste van die ensiem aktiwiteit het in die selwand voorgekom, terwyl laer vlakke uit die intrasellulêre area ge-isoleer is en geen ensiem aktiwiteit in die medium as uitgeskeide ensiem voorgekom het nie. Die gemengde kultuur fermentasies het gelei tot wynprodukte met beduidend anderse chemiese samestelling in vergelyking met S. cerevisiae fermentasie. L. thermotolerans en L. lanzarotensis gemengde kultuur fermentasies het soortgelyke wyne met hoër produksie van algemene verbindings, insluitend isoamiel alkohol, butanol, en etiel fenielasetaat, opgelewer. L. fermentati het oënskynlik wyne geproduseer wat heelwat anders is as die ander Lachancea spp., met vlakke van asynsuur wat moontlik ‘n aanduiding is dat die spesie ‘n potensiele bederf mikroorganisme is. Hierdie studie het nuwe inligting oor die relatief onbestudeerde Lachancea spp. getoon, waar hul wynkundige potensiaal uitgelig is deur die vermoë om β-glukosidase ensieme uit te druk gedurende fermentasies en om wyne te produseer wat beduidend anders is as die van S. cerevisiae.Master
Unravelling the Vitis vinifera L. cv Pinotage fermentation microbiome across the Western Cape
No full textThesis (MScAgric)--Stellenbosch University, 2023.ENGLISH ABSTRACT: Over the past decade there has been growing interest in understanding the geographic distribution of wine fermentation microbiota due to their contribution to wine aroma and the belief that microorganisms contribute to wine terroir and therefore the distinctiveness particularly of spontaneously fermented wines. Studies conducted in many wine producing regions and on different grapevine cultivars have shown that wine fermentation microbial communities are influenced by vineyard geography, grape variety and vintage. Although South Africa is considered a major wine producing country, little is known about the microbial diversity in its vineyards. Consequently, the current study investigated the geographical distribution of the microbiota associated with Vitis vinifera L. cv Pinotage, a uniquely South African cultivar generated by crossing Hermitage and Pinot noir. Pinotage grapes were collected from 32 vineyards across 9 districts and processed following standard winemaking practices at the Stellenbosch University experimental cellar. The chemical and microbial community composition of the resulting grape must were compared. Furthermore, spontaneous fermentations were conducted, and the microbial population dynamics were monitored. The chemical compositions of the Pinotage finished wines were also analysed. Based on ARISA profiles, the bacterial communities were similar between regions and districts, and smaller differences that were found could be attributed to chance. Phylogenetic surveys based on amplicon sequencing revealed an increase in bacterial dissimilarities over distance. Vineyards were found to be mostly similar with the genera Acetobacter, Bacillus, Enterobacter, Gluconobacter, Kozakia, Pantoea, Pseudomonas and Streptomyces being the main contributors to the similarities. In contrast, ARISA data showed that fungal communities were different and displayed increasing dissimilarities over distance. Differences were found to be greater than those expected by chance. However, phylogenetic surveys showed similarities between regions and variance of vineyards with individual districts. The similarities that were found were attributed to the genera Mycosphaerella, Penicillium and Aspergillus. No significant differences were found between the yeast communities over distance, likely due to the genus Torulospora, which was in high abundance. For within vineyard analysis, blocks hosted some unique bacterial and fungal operational taxonomic units, and differences were theorised to be due to mesoclimate, and differences in harvest dates. All wines fermented to dryness, although fermentative yeasts were not found in all must samples. It was theorised that yeast species may have been inoculated in musts from the cellar equipment used or cellar environment. The bacterial and fungal dynamics were monitored at different periods in fermentation and general decline in OTUs from musts to finished wines was found. Finished wine samples were found to have no significant differences between them. Broad standard deviation in chemical samples was found and attributed to biological replicates and possible oxidation of samples. Overall, this work provides evidence for the natural microbial population associated with Pinotage musts and adds to the growing information on the microbial biogeography of grape musts. This research could inform Pinotage management practices and could help to enhance Pinotage wine distinctiveness.AFRIKAANSE OPSOMMING: Oor die afgelope dekade was daar toenemende belangstelling in die begrip van die geografiese
verspreiding van wynfermentasiemikrobiota as gevolg van hul bydrae tot wynaroma en die oortuiging
dat mikroörganismes bydra tot wynterroir en dus die eiesoortigheid van veral spontaan
gefermenteerde wyne. Studies wat in baie wynproduserende streke en op verskillende
wingerdkultivars uitgevoer is, het getoon dat wynfermentasie mikrobiese gemeenskappe deur
wingerdgeografie, druifvariëteit en oesjaar beïnvloed word. Alhoewel Suid-Afrika as 'n groot
wynproduserende land beskou word, is min bekend oor die mikrobiese diversiteit in sy wingerde.
Gevolglik het die huidige studie die geografiese verspreiding van die mikrobiota wat met Vitis
vinifera L. cv Pinotage geassosieer word, ondersoek, 'n unieke Suid-Afrikaanse kultivar wat
gegenereer word deur Hermitage en Pinot noir te kruis.
Pinotage druiwe is van 32 wingerde oor 9 distrikte versamel en volgens standaard wynmaakpraktyke by
die Universiteit Stellenbosch eksperimentele kelder verwerk. Die chemiese en mikrobiese
gemeenskapsamestelling van die gevolglike druiwemos is vergelyk. Verder is spontane fermentasies
uitgevoer, en die mikrobiese populasiedinamika is gemonitor. Die chemiese samestellings van die
Pinotage voltooide wyne is ook ontleed.
Gebaseer op ARISA-profiele was die bakteriese gemeenskappe soortgelyk tussen streke en distrikte,
en kleiner verskille wat gevind is kon aan toeval toegeskryf word. Filogenetiese opnames gebaseer
op amplikonvolgordebepaling het 'n toename in bakteriese ongelykhede oor afstand aan die lig
gebring. Daar is gevind dat wingerde meestal soortgelyk is met die genera Acetobacter, Bacillus,
Enterobacter, Gluconobacter, Kozakia, Pantoea, Pseudomonas en Streptomyces wat die belangrikste
bydraers tot die ooreenkomste was. Daarteenoor het ARISA-data getoon dat swamgemeenskappe
verskillend was en toenemende verskille oor afstand vertoon. Daar is gevind dat verskille groter is
as wat toevallig verwag is. Filogenetiese opnames het egter ooreenkomste tussen streke en variasie
van wingerde met individuele distrikte getoon. Die ooreenkomste wat gevind is, is toegeskryf aan
die genera Mycosphaerella, Penicillium en Aspergillus. Geen betekenisvolle verskille is gevind
tussen die gisgemeenskappe oor afstand nie, waarskynlik as gevolg van die genus Torulospora, wat in
groot oorvloed was. Vir binne wingerdontleding, het blokke 'n paar unieke bakteriese en swam
operasionele taksonomiese eenhede gehuisves, en verskille is teoretiseer as gevolg van mesoklimaat,
en verskille in
oesdatums.
Alle wyne het tot droog gegis, hoewel fermentatiewe giste nie in alle mosmonsters gevind is nie.
Daar is teoretiseer dat gisspesies moontlik in most ingeënt is uit die keldertoerusting wat
gebruik is of kelderomgewing. Die bakteriese en swamdinamika is tydens verskillende tydperke in
fermentasie gemonitor en algemene afname in OTU's van mos tot klaarwyne is gevind. Daar is gevind
dat voltooide wynmonsters geen beduidende verskille tussen hulle het nie. Breë standaardafwyking in
chemiese monsters is gevind en toegeskryf aan biologiese herhalings en moontlike oksidasie van
monsters.
Oor die algemeen verskaf hierdie werk bewyse vir die natuurlike mikrobiese populasie wat met
pinotagemos geassosieer word en dra by tot die groeiende inligting oor die mikrobiese biogeografie
van druiwemos. Hierdie navorsing kan Pinotage-bestuurspraktyke inlig en kan help
om Pinotage-wyn se eiesoortigheid te verbeter.Master
Evaluating the effect of environmental parameters on the dynamics of the wine yeast consortium
No full textThesis (PhDAgric)--Stellenbosch University, 2018.ENGLISH ABSTRACT: Wine fermentation is a complex biochemical process which is characterized by the sequential
development of various weakly and strongly fermentative yeast species. Thus, in such a multispecies consortium, individual species interact with one another and with their environment. Consequently, final chemical composition of wine will be affected significantly by the contribution of individual species as well as yeast-yeast interactions present in a wine consortium. The contribution of individual strain in the wine consortium is affected by several biotic (ecological interactions, killer factors, and grape variety) as well as abiotic parameters (temperature, sulphur dioxide, oxygen and nutrient availability). However, each strain will be affected differently by the combination of these parameters. Previous studies in wine fermentations have mainly focused on mixed culture fermentations composed of two species. Thus, fundamental rules underlying the effect of these parameters in a multi-species ecosystem are not fully understood. To decipher the principles that govern the complex wine ecosystem, a simplified model consortium comprising eight species commonly encountered in South African grape microbiota was established. An Automated ribosomal intergenic spacer analysis (ARISA) method was also developed in order to monitor population dynamics of the yeast consortium. The influence of presence of Saccharomyces cerevisiae as a biotic stress was investigated on the dynamics of yeast consortium in synthetic must using plating method and ARISA. Furthermore, the yeast consortium was used as an inoculum in Chenin blanc grape must where the population dynamics were monitored by plating method. The results confirmed that a selective pressure applied by the keystone species, S. cerevisiae modified the pattern of population dynamics. Wine ecosystem was characterized by supportive and inhibitory interactions. Furthermore, in spite of the differences between the two grape matrices, a similar pattern of population dynamics was observed in both fermentations. This observation suggested broad applicability of the model consortium to study the ecological interactions in the wine fermentation. In the next step, the variation in initial cell densities of each member of the consortium was used as a tool to untangle the contribution of individual strain in the population dynamics and wine aroma. The data suggest that S. cerevisiae applied a selective pressure to suppress the growth of main competitor in the wine ecosystem. Moreover, the presence of individual non-Saccharomyces species at a higher cell density, favoured the growth of some non-Saccharomyces species while suppressing the growth of others in the yeast consortium.
Lastly, the effect of temperature and sulphur addition on the dynamics of the yeast consortium was evaluated in the synthetic must and real grape must fermentations.
The results demonstrated that ecological interactions are largely independent of the matrix, confirming that the constructed multispecies consortium is a robust model that can be used as a tool to predict microbial behavior from
a simple ecosystem to the complex natural environment. Furthermore, the effect of temperature and sulphur dioxide on the growth of non-Saccharomyces species was species/strain dependent.
The results suggest that environmental parameters modify the pattern of population dynamics. However, ecological interactions seem to drive the wine ecosystem. The current study for the first time revealed the potential of a multi-species yeast consortium in understanding the ecological interactions in wine fermentation.AFRIKAANSE OPSOMMING: Wynfermentasie is 'n komplekse biochemiese proses wat deur die opeenvolgende ontwikkeling
van verskeie swak en sterk fermenterende gis spesies gekarakteriseer word. Dus, in so 'n multispesie konsortium, is daar 'n interaksie tussen die individuele spesies en tussen die spesies en hul omgewings. Gevolglik sal die finale chemise komposisie van die wyn beduidend deur die bydrae van individuele gis spesies en die gis-gis interaksies teenwoordig in die wyn beïnvloed word. Die bydrae van individuele gisrasse in die wynkonsortium word deur verskeie biotiese (ekologiese
interaksies, “killer” faktore en druifvariëteit) sowel as abiotiese faktore (temperatuur, swaweldioksied, suurstof en die beskikbaarheid van voedingstowwe) beïnvloed. Elke gisras sal
egter verskillend deur die kombinasie van die faktore beïnvloed word. Vorige studies wat handel oor wynfermentasie het hoofsaaklik op gemengde kultuur fermentasies met twee gis spesies gefokus. Dus is die onderliggende fundamentele reëls van die faktore in 'n multi-spesie ekosisteem nie volledig verstaan nie.
Om die beginsels wat die komplekse wyn ekosisteem regeer te ontsyfer, is 'n vereenvoudigde model konsortium, bestaande uit agt spesis wat algemeen voorkom in Suid-Afrikaanse
druifmikrobiota, gevestig. 'n Outomatiese ribosomale intergeniese spasiëringsanalise (ORISA) metode was ook ontwikkel om die bevolkings dinamika van die giskonsortium te monitor. Die invloed van die teenwoordigheid van Saccharomyces cerevisiae as 'n biotiese stres faktor op die
dinamika van die giskonsortium in 'n sintetiese druiwemos was ondersoek deur die uitplaat metode en ORISA te gebruik. Die giskonsortium was verder gebruik as 'n inokulum in Cenin blanc druiwe mos waar die bevolkingsdinamika deur die uitplaat metode gemonitor was. Die resultate bevestig dat die geselekteerde druk wat deur die hoeksteen spesies, S. cerevisiae, uitgevoer was die patroon van die bevolkingsdinamika verander het. Die wynekosisteem was gekarakteriseer deur die ondersteunende en inhiberende interaksies. Ten spyte van die verskille tussen die twee
druifmatrikse is 'n soortgelyke patroon van bevolkingsdinamika in beide fermentasies waargeneem. Hierdie observasie stel die wye toepassing van die model konsortium om die ekologiese interaksies in wynfermentasie te bestudeer voor. In die volgende stap is die variasie in aanvanklike seldigthede van elke lid van die konsortium gebruik as 'n “tool” om die individuele bydrae van elke individuele gisras in die bevolkingsdinamika en wynaroma te bepaal. Die data stel voor dat S. cerevisiae 'n selektiewe druk toegepas het om die groei van die hoof kompeteerder in die wynekosisteem te onderdruk. Die teenwoordigheid van individuele nie-Saccharomyces spesies teen 'n hoër seldigtheid, het ook die groei van sommige nie-Saccharomyces spesies bevoordeel terwyl dit die groei van ander in die giskonsortium onderdruk het.
Laastens is die effek van temperatuur en swawel toevoegings op die dinamika van die giskonsortium geëvalueer in die sintetiese druiwe mos en werklike druiwe mos fermentasies. Die resultate demonstreer dat ekologiese interaksies grootliks onafhanklik is van die matriks, wat bevestig dat die bewerkstelling van 'n multi-spesies konsortium 'n robuuste model is wat gebruik kan word as 'n tool om die mikrobiale gedrag van 'n eenvoudige ekosisteem tot 'n komplekse
natuurlike omgewing kan voorspel. Daarbenewens is die effek van temperatuur en swaweldioksied op die groei van nie-
Saccharomyces spesies afhanklik van die spesies/ras. Die resultate stel voor dat omgewings faktore die patroon van bevolkingsdinamika verander. Nietemin blyk dit dat die ekologiese interkasies die wynekosisteem dryf. Die huidige studie het vir die eerste keer die potensiaal van 'n multi-spesies giskonsortium onthul om die ekologiese interaksies in wynfermentasie te verstaan.Doctora
Characterization of Chenin Blanc wines produced by natural fermentation and skin contact : focus on application of rapid sensory profiling methods
No full textThesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Producers of South African (SA) dry and semi-dry Chenin blanc table wines are currently
experimenting with winemaking techniques to modulate the flavours of the predominantly fruity
styles of this genre. An important stage during wine style development is sensory profiling
paired with consumer acceptance testing, before wine is produced on industrial scale. With
those aforementioned goals in mind, this study was conducted in partnership with two
commercial SA wine cellars.
The main focus of the study was an investigation into the treatment effects of two winemaking
techniques, respectively grape skin contact and natural fermentation, on the sensory profiles of
experimentally produced Chenin blanc wines. Results obtained with descriptive sensory
analysis (DA) of the wines were compared to those obtained by two rapid sensory profiling
methods, namely projective mapping (PM) and frequency of attribute citation (FC). A consumer
preference study was also done on the wines. In order to understand the treatment effects
better, the dominant non-Saccharomyces yeasts that were present during the natural
fermentations were identified using polymerase chain reaction (PCR), while the major volatile
chemical compounds were identified with chromatography and mass spectrometry.
The sensory and chemical profiles of the naturally fermented wines were significantly different
from those of the inoculated wines. PCR analysis identified some of the yeasts present during
alcoholic fermentation. In comparison to the inoculated fermented wines, the naturally
fermented wines were generally perceived to have more intense and riper tropical fruity aromas,
with enhanced sweetness and reduced intensities of sourness, bitterness and astringency.
The wines fermented on the skins (FoS) had lower ester and volatile thiol concentrations than
the control wines (with no skin contact) and limited skin contact wines. Sensory attributes linked
to the FoS wines included aromas of dried fruit, dried grass and a vegetative character, with an
increased sour and bitter taste and astringent mouthfeel. In contrast, the wines that were
produced with limited skin contact (12 hours) retained their tropical fruity aromas better than the
FoS wines. Limited skin contact seemed to have had a less harsh effect on the taste and
mouthfeel than the FoS wines. A consumer study was done to establish a Generation Y
consumer group’s (18-35 years) preference for the different treated wines. Overall, the naturally
fermented wines, which were described as having a strong tropical fruit character, were
preferred. The FoS wines were generally disliked by the consumers. Results obtained from the three sensory analysis methods, respectively DA, PM and FC, were
similar, thereby confirming the suitability of the rapid methods PM and FC, to extract qualitative
information from the sensory profiling of white wine.
The results of this study made a significant contribution towards validation of rapid sensory
methods for wine evaluation, which are particularly valuable in the context of sustainability and
technology transfer to research and industry alike. The knowledge gained on the chemical
profiles of SA Chenin blanc is novel and this is one of the first reports on the volatile thiol
content of SA Chenin blanc wine.AFRIKAANSE OPSOMMING: Produsente van Suid-Afrikaanse (SA) droë en semi-droë Chenin blanc tafelwyne
eksperimenteer tans met wynmaaktegnieke om die oorwegend vrugtige style van hierdie genre
te varieer. ‘n Belangrike fase van wynstylontwikkeling is sensoriese profilering van die produkte
met gepaardgaande verbruikersaanvaardingstoetse, voordat die wyne op industriële skaal
geproduseer word. Met dié bogenoemde doelwitte in gedagte, was hierdie studie in
vennootskap met twee kommersiële SA wynkelders gedoen.
Die hooffokus van die studie was om die invloed van twee wynmaaktegnieke, onderskeidelik
druifdopkontak en natuurlike fermentasie, op die sensoriese profiele van eksperimenteel
geproduseerde Chenin blanc wyne te ondersoek. Resultate wat met beskrywende sensoriese
analise (DA) van die wyne verkry is, is vergelyk met dié wat deur twee vinniger sensoriese
profileringsmetodes metodes, naamlik projektiewe kartering (PM) en frekwensie van
kenmerkaanhaling (FC) verkry is. 'n Verbruikervoorkeurstudie is ook op die wyne gedoen. Ten
einde die behandelingseffekte beter te verstaan, is die dominante nie-Saccharomyces giste wat
teenwoordig was tydens die natuurlike fermentasie geïdentifiseer met behulp van die
polimerasekettingreaksie (PCR), terwyl die vernaamste vlugtige chemiese verbindings
geïdentifiseer is met chromatografie en massaspektrometrie.
Die sensoriese en chemiese profiele van die natuurlike gefermenteerde wyne was beduidend
anders as dié van die geiinokuleerde wyne. PCR analise het sommige giste wat teenwoordig
was tydens alkoholies fermentasie geïdentifiseer. In vergelyking met die geiinokuleerde wyne,
het die natuurlik gefermenteerde wyne intenser en ryper tropiese vrugtige aromas getoon, met
‘n verhoogde perspesie van soetheid en laer intensiteite van suurheid, bitterheid en vrankheid. Die wyne wat berei is deur fermentasie op die druifdoppe (FoS) het laer konsentrasies van
esters en vlugtige swawelverbinding gehad, as die kontrole wyne (geen dopkontak) en beperkte
dopkontak wyne. Sensoriese eienskappe gekoppel aan die FoS wyne was geasssosieer met
gedroogde vrugte, gedroogde gras en 'n vegetatiewe aroma, met gepaardgaande verhoogde
suur en bitter smaakpersepsies en ‘n frank mondgevoel. In teenstelling, het die wyne wat
geproduseer is met 'n beperkte dopkontak (12 uur) hul tropiese vrugtige aroma beter behou as
die FoS wyne. Beperkte dopkontak het ook ‘n minder negatiewe uitwerking op die
smaakpersepies van bitterheid en vrankheid gehad. ‘n Verbruikerstudie is gedoen om 'n groep
jong Generasie Y verbruikers (18-35 jaar) se voorkeure vir die verskillende behandelings te
bepaal. Oor die algemeen is die natuurlike gefermenteerde wyne, wat beskryf is met 'n sterk
tropiese vrugtekarakter verkies, terwyl die groep nie van die FoS wyne gehou het nie. Resultate wat verkry is met drie sensoriese analise metodes, onderskeidelik DA, PM en FC,
was soortgelyk en die geskiktheid van die vinniger metodes, PM en FC, om kwalitatiewe
inligting van witwyn se sensoriese eienskappe te verkry, is bevestig.
Die resultate verkry met hierdie studie maak ‘n beduidende bydrae tot die validering van
vinniger sensoriese metodes vir wynevaluering, wat veral waardevol is in die konteks van
volhoubaarheid en tegnologieoordrag na navorsing en die industrie.
Die nuwe kennis wat in hierdie studie gegenereer is met die chemiese profilering van SA
Chenin blanc wyn is baie waardevol en hierdie is een van die eerste narvorsingsprojekte oor die
inhoud van vlugtige swawelverbings in SA Chenin blanc wyn
Characterization of cv. Cabernet Sauvignon (Vitis vinifera L.): the contribution of Ecklonia maxima seaweed extract
No full textThesis (MScAgric)--Stellenbosch University, 2022.ENGLISH ABSTRACT: Conventionally grape cultivation makes use of chemical fertilizers and synthetic pesticides to
sustain growth and ensure fruit production ultimately resulting in more resistant grapevines to
pests and diseases. However, their application also imposes a negative impact on human health and
the environment. Therefore, agricultural sustainability is increasingly encouraged to ensure food
safety and the conservation of the environment. In this regard viticulture is urgently seeking
alternative solutions to increase sustainability. Biostimulants is a novel and sustainable tool
which may be a good alternative to reduce the chemical-dependency typical of conventional
cultivation practices, thereby supporting eco-friendly methods to increase agricultural outputs,
via fruit quality, and resistance to abiotic stress.
Biostimulants is the term given to a range of products, of natural origin, known to promote
vegetative and reproductive growth as well as increase tolerance against biotic and abiotic stress.
Seaweed extracts, a sub-category of biostimulants, have been highlighted as one of the most
promising groups of biostimulants for use in viticulture. Commercial seaweed extract products are
often derived from Ascophyllum nodosum (often located on the coasts of the North Atlantic), with
studies on its effects on plant physiology being very popular and well-researched. The South
African species, Ecklonia maxima, and its effects on wine grapes, is however under researched.
The aim of this study was to evaluate the influence of Ecklonia maxima (EM) seaweed extract on vine
physiology, grape and wine quality within in the South African viticultural context on Vitis
vinifera
L. Cabernet Sauvignon. Foliar applications of a commercial Ecklonia maxima seaweed extract
biostimulant, under the trade name Kelpak ®, were conducted before flowering, at fruit set and at
véraison under two irrigation scenarios ((i) irrigated and (ii) non-irrigated). Grapevine
photosynthetic capacity, chlorophyll content and water status were not impacted by the application
of Ecklonia maxima. Leaf area and fruit composition were positively impacted by the treatments. The
combination of EM applications and irrigation resulted in significantly higher leaf area.
Furthermore, the leaf area continuously increased throughout the season which is the first study to
report this finding. The latter resulted in increased concentrations of sugars, organic acids,
amino acids and phenolic content in grape berries. Surprisingly, the increased concentrations of
the metabolites at harvest were not reflected in the wine parameters (final alcohol content (%),
wine pH and total acidity and phenolic content) made in this study. This suggests that fermentation
kinetics altered the extraction of these metabolites.
Our findings correspond with that of the use of Ascophylum nodosum which resulted in increased
fruit quality. The study was only conducted in one season and subsequent seasons should be
conducted to have a clear understanding of the photosynthetic, water use, and metabolic pathways
induced when using Ecklonia maxima. Furthermore, Ecklonia maxima should be used in conjunction
with conventional farming to enhance grapevine functioning and fruit quality.AFRIKAANSE OPSOMMING: Konvensionele druiweverbouing maak gebruik van chemiese kunsmis en sintetiese plaagdoders om groei
te onderhou en vrugteproduksie te verseker wat uiteindelik lei tot meer weerstandbiedende wingerde
teen plae en siektes. Die toepassing daarvan het egter ook 'n negatiewe impak op menslike
gesondheid en die omgewing. Daarom word landbouvolhoubaarheid toenemend aangemoedig om
voedselveiligheid en die bewaring van die omgewing te verseker. In hierdie verband soek wingerdbou
dringend alternatiewe oplossings om volhoubaarheid te verhoog. Biostimulante is 'n nuwe en
volhoubare hulpmiddel wat 'n goeie alternatief kan wees om die chemiese afhanklikheid tipies van
konvensionele verbouingspraktyke te verminder, en sodoende eko-vriendelike metodes te ondersteun om
landbou-uitsette te verhoog, deur vrugkwaliteit, en weerstand teen abiotiese stres.
Biostimulante is die term wat gegee word aan 'n reeks produkte van natuurlike oorsprong, wat bekend
is om vegetatiewe en reproduktiewe groei te bevorder, asook om verdraagsaamheid teen biotiese en
abiotiese stres te verhoog. Seewierekstrakte, 'n sub-kategorie van biostimulante, is uitgelig as
een van die mees belowende groepe biostimulante vir gebruik in wingerdbou. Kommersiële
seewierekstrakprodukte word dikwels afkomstig van Ascophyllum nodosum (dikwels geleë aan die kus
van die Noord-Atlantiese Oseaan), met studies oor die uitwerking daarvan op plantfisiologie wat
baie gewild en goed nagevors is. Die Suid-Afrikaanse spesie, Ecklonia maxima, en die uitwerking
daarvan op wyndruiwe, word egter onder navorsing gedoen.
Die doel van hierdie studie was om die invloed van Ecklonia maxima (EM) seewierekstrak op
wingerdfisiologie, druif- en wynkwaliteit binne in die Suid-Afrikaanse wingerdboukonteks op Vitis
vinifera L. Cabernet Sauvignon te evalueer. Blaartoedienings van 'n kommersiële Ecklonia maxima
seewierekstrak biostimulant, onder die handelsnaam Kelpak ®, is voor blom, by vrugset en op
verraison uitgevoer onder twee besproeiingscenario's ((i) besproei en (ii) Nie-besproei). Wingerd
fotosintetiese kapasiteit, chlorofil inhoud en water status is nie beïnvloed deur die toediening
van Ecklonia maxima nie. Blaaroppervlakte en vrugtesamestelling is positief deur die behandelings
beïnvloed. Die kombinasie van EM-toedienings en besproeiing het aansienlik groter
blaaroppervlakte tot gevolg gehad. Verder het die blaaroppervlak voortdurend deur die seisoen
toegeneem, wat die eerste studie is wat hierdie bevinding rapporteer. Laasgenoemde het gelei tot
verhoogde konsentrasies van suikers, organiese sure, aminosure en fenoliese inhoud in
druiwebessies. Verbasend genoeg is die verhoogde konsentrasies van die metaboliete tydens oes nie
weerspieël in die wynparameters (finale alkoholinhoud (%), wyn pH en totale suur en fenoliese
inhoud) wat in hierdie studie gemaak is nie. Dit dui daarop dat fermentasiekinetika die ekstraksie
van hierdie metaboliete verander het.
Ons bevindinge stem ooreen met dié van die gebruik van Ascophylum nodosum wat gelei het tot
verhoogde vrugkwaliteit. Die studie is slegs in een seisoen uitgevoer en daaropvolgende seisoene
moet uitgevoer word om 'n duidelike begrip te hê van die fotosintetiese, watergebruik en
metaboliese weë wat geïnduseer word wanneer Ecklonia maxima gebruik word. Verder moet Ecklonia
maxima saam met konvensionele boerdery gebruik word om wingerd se funksionering en vrugkwaliteit te
verbeter.Master
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