Impact of exogenous thiamine on Kluyveromyces marxianus under oenological conditions
| dc.contributor.advisor | Divol, Benoit | en_ZA |
| dc.contributor.author | Labuschagne, Pieter Willem Jacobus | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology. | en_ZA |
| dc.date.accessioned | 2020-11-30T15:18:15Z | |
| dc.date.accessioned | 2021-02-01T07:56:49Z | |
| dc.date.available | 2020-11-30T15:18:15Z | |
| dc.date.available | 2021-02-01T07:56:49Z | |
| dc.date.issued | 2020-12 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Managed inoculation of non-Saccharomyces yeast species is regarded as a practical way to introduce new characteristics to wine. However, these yeasts struggle to survive until fermentation is complete. The non- Saccharomyces strain, Kluyveromyces marxianus IWBT Y885, was recently isolated from South African grape juice and was partially characterised for winemaking purposes. This yeast strain displays relatively good fermentation ability as well as commercially relevant characteristics such as the production of strong pectinase activity and high phenylethanol and phenylethyl acetate production levels. In order to consider this strain for industrial winemaking, it is important to ensure its prolonged survival and good fermentation performance. A key factor for survival, growth and sustained metabolic activity of all yeasts is their nutrient requirements. Thus, identifying nutrients that are essential for maximising fermentation performance, and subsequently ensuring adequate levels of nutrients, is a means to ensure significant contribution of yeast to wine properties. This study aimed to identify essential nutrients, other than previously studied sugars and nitrogen, for maximum impact of K. marxianus Y885, as well as to characterise the outcomes of their utilisation. A multifactorial experimental design was employed to investigate the impact of nutrient concentrations on fermentation performance with K. marxianus Y885 in synthetic must. Exogenous thiamine concentration was determined to be the most significant factor impacting fermentation performance of K. marxianus Y885. The response to exogenous thiamine concentration for K. marxianus Y885 and S. cerevisiae EC1118 was compared in terms of population viability, fermentation rate, total sugars utilised, thiamine assimilation kinetics, and final wine composition. A saturation effect for initial thiamine concentration of K. marxianus Y885 fermentations was characterised, with a maximum fermentation rate and over 90% of available sugars utilisation obtained at 0.25 mg/L. A delayed uptake of thiamine at higher concentrations for K. marxianus Y885 suggested differential regulation of thiamine uptake compared to S. cerevisiae EC1118. In addition, different trends in metabolites produced between species suggest that thiamine concentration impacts the carbon metabolic flux differently in these two yeasts. To assess how this knowledge would translate to industrial winemaking conditions, the effect of maximum legal thiamine concentration to K. marxianus Y885/S. cerevisiae EC1118 sequential fermentations at semi-industrial scale in real grape must was investigated. No effect of thiamine supplementation on fermentation performance was observed, most likely as a result of the high native must thiamine content and lack of indigenous organisms that may compete for thiamine. However, thiamine concentration clearly differentially affected major volatile production of K. marxianus Y885 and S. cerevisiae EC1118. Notably, an increased fusel alcohol production of K. marxianus Y885 resulted from thiamine addition, which positively affects wine aroma. This study provides relevant information that may be used to ensure optimal utilisation of K. marxianus Y885 in oenology and aids in our understanding of how thiamine alters yeast metabolism. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Bestuurde innokulasie van nie-Saccharomyces gisspesies word beskou as 'n praktiese metode om nuwe eienskappe in wyne te bewerkstellig. Hierdie groep giste sukkel egter om te oorleef totdat die fermentasieproses voltooi is. Die nie-Saccharomyces gisstam, Kluyveromyces marxianus IWBT Y885, is onlangs vanuit Suid-Afrikaanse druiwesap geïsoleer en is gedeeltelik gekarakteriseer vir wynmaakdoeleindes. Hierdie gisstam vertoon relatiewe goeie fermentasievermoë, sowel as eienskappe van waarde vir kommersiële gebruik, insluitend die produksie van sterk pektinase-aktiwiteit en hoë produksievlakke van die aromaverbindings, fenieletanol en fenieletielasetaat. Ten einde hierdie gisstam vir industriële wynmaak te oorweeg, is dit belangrik om volgehoue oorlewing en goeie fermentasieverrigting te verseker. 'n Sleutelfaktor vir die groei, oorlewing en volgehoue metaboliese aktiwiteit van alle giste is hul voedingsbehoeftes. Daarom is die identifisering van voedingstowwe wat noodsaaklik vir maksimum fermentasieverrigting is, tesame met toesiening na voldoende beskikbare konsentrasies van hierdie voedingstowwe, 'n praktiese benadering om die bydrae van giste tot wyneienskappe te verseker. Hierdie studie het ten doel gehad om voedingstowwe te identifiseer wat noodsaaklik is vir die maksimum impak van K. marxianus Y885 op wyneienskappe, asook om die uitkomste van die benutting van die voedingstowwe te karakteriseer. 'n Multifaktoriale eksperimentele model is gebruik om die impak van voedingstofkonsentrasies op fermentasieverrigting van K. marxianus Y885 in sintetiese druiwesap te ondersoek. Die eksogene tiamienkonsentrasie is as die faktor wat die fermentasieverrigting van K. marxianus Y885 mees beduidend beïnvloed het vasgestel. Die reaksie van K. marxianus Y885 en S. cerevisiae EC1118 op eksogene tiamienkonsentrasie is vergelyk in terme van populasiegroei, fermentasiesnelheid, totale suiker assimilasie, tiamienassimilasie kinetika en finale wynsamestelling. 'n Versadigingseffek vir die aanvanklike tiamienkonsentrasie vir K. marxianus Y885 fermentasies is gekarakteriseer, waar die maksimum fermentasiesnelheid asook meer as 90% van die beskikbare suikers geassimileer is by 0.25 mg/L. 'n Vertraagde opname van tiamien by hoër konsentrasies vir K. marxianus Y885 stel differensiële regulering van opname in vergelyking met S. cerevisiae EC1118 voor. Daarbenewens dui verskillende tendense in metabolietproduksie tussen spesies daarop dat tiamienkonsentrasie koolstofmetabolisme van hierdie twee giste verskillend affekteer. Ten einde te bepaal hoe hierdie kennis oordra na industriële wynmaaktoestande, is die effek van maksimum wettige tiamien toevoeging op K. marxianus Y885/S. cerevisiae EC1118 opeenvolgende fermentasies op ‘n semi-industriële skaal in regte druiwesap ondersoek. Geen effek van tiamien toevoeging op die fermentasieverrigting is waargeneem nie, waarskynlik as gevolg van ‘n hoë tiamieninhoud reeds aanweesig in die sap voor toevoeging, asook die gebrek aan inheemse organismes wat vir opname van tiamien kan meeding. Die tiamienkonsentrasie het egter duidelik die produksie van aromaverbindings vir K. marxianus Y885 en S. cerevisiae EC1118 differensiëel beïnvloed. Veral opmerklik was 'n verhoogde produksie van fuselalkohole vir K. marxianus Y885 met hoër timienkonsentrasies, wat wynaroma positief beïnvloed. Hierdie studie verskaf relevante inligting wat benut kan word om die optimale gebruik van K. marxianus Y885 vir wynmaak te verseker, sowel as om ons kennis te verbreed aangaande die effek van tiamien op gismetabolisme. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.format.extent | xi, 108 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/109480 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Kluyveromyces marxianus | en_ZA |
| dc.subject | Saccharomyces cerevisiae | en_ZA |
| dc.subject | Wine -- Fermentation | en_ZA |
| dc.subject | Yeast nutrition | en_ZA |
| dc.subject | Thiamine | en_ZA |
| dc.subject | Yeast -- Effect of stress on | en_ZA |
| dc.subject | Grapes -- Effect of stress on | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Impact of exogenous thiamine on Kluyveromyces marxianus under oenological conditions | en_ZA |
| dc.type | Thesis | en_ZA |