The utilisation of nitrogenous compounds by commercial non-Saccharomyces yeasts associated with wine
| dc.contributor.advisor | Divol, Benoit | en_ZA |
| dc.contributor.advisor | Bauer, Florian | en_ZA |
| dc.contributor.author | Prior, Kelly Jade | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. | en_ZA |
| dc.date.accessioned | 2017-11-20T11:00:35Z | |
| dc.date.accessioned | 2017-12-11T11:12:58Z | |
| dc.date.available | 2017-11-20T11:00:35Z | |
| dc.date.available | 2017-12-11T11:12:58Z | |
| dc.date.issued | 2017-12 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2017. | en_ZA |
| dc.description.abstract | ENGLISH SUMMARY: Nitrogen is an essential element for yeast growth and metabolism. During winemaking, the uptake of nitrogen sources ensures the completion of alcoholic fermentation while participating in the production of aroma compounds. Preference for certain nitrogen sources has been determined for Saccharomyces cerevisiae, the main wine yeast, but not in other yeast species, collectively referred to as non-Saccharomyces yeasts. Yet, the latter are becoming increasingly used in industry in combination with S. cerevisiae and the preferences of these yeasts should also be investigated in order to ensure optimal fermentation ability and aroma compound production. This could unravel possible competition between yeast species and consequently potential needs for supplementation to avoid stuck fermentations and production of off-aroma compounds. This study investigated the nitrogen source preferences of a number of commercial non-Saccharomyces yeasts (Pichia kluyveri Viniflora® FootZen™, Torulaspora delbrueckii Biodiva™ TD291, Metschnikowia pulcherrima Flavia® MP346 and Lachancea thermotolerans Viniflora® Concerto™) by conducting pure culture fermentations in a synthetic grape must medium with nitrogen sources present at equal assimilable nitrogen concentrations. Uptake varied between yeast species, however P. kluyveri and M. pulcherrima showed similar uptake trends, as did L. thermotolerans and T. delbrueckii. Nitrogen uptake was also proportional to CO2 release, sugar consumption and yeast growth. L. thermotolerans and T. delbrueckii took up a greater amount of the nitrogen sources than P. kluyveri and M. pulcherrima, as well as at a faster rate. Variations in amino acid preferences between yeast species were observed. The presence of ammonium was shown to affect the % uptake of certain amino acids for the different species as well as the onset of amino acid uptake for T. delbrueckii. Sequential fermentations with grape must-like nitrogen concentrations revealed that L. thermotolerans and T. delbrueckii pose a larger problem regarding competition with S. cerevisiae compared to P. kluyveri and M. pulcherrima. This was reflected in fermentation kinetics of sequential fermentations as well as the levels of aroma compound production. This suggests that sequential fermentations with L. thermotolerans and T. delbrueckii may require higher nitrogen source supplementation than P. kluyveri and M. pulcherrima for S. cerevisiae to complete fermentation as well as increase the concentration of desirable aroma compounds. Some correlations were observed regarding nitrogen source uptake and aroma compounds produced, for example the uptake of threonine and resulting propanol production. The data showed that, after inoculation with S. cerevisiae Lalvin® EC1118, the population of non-Saccharomyces yeasts declined and the cells probably autolyse, thereby releasing nitrogen sources that can be taken up by S. cerevisiae. This study improved our knowledge of non-Saccharomyces yeasts’ nitrogen source preferences, and establishes some links between nitrogen source uptake and aroma compound production. Competition between yeasts was also demonstrated and linked with nitrogen uptake and fermentation ability. | en_ZA |
| dc.description.abstract | AFRIKAANS OPSOMMING: Stikstof is ‘n essensiële element vir gis groei en gis metabolisme. Gedurende die wynmaak proses, verseker die opname van stikstof bronne die voltooiing van alkoholiese fermentasie terwyl die aroma verbindings geproduseer word. Voorkeur vir sekere stikstof bronne is vasgestel vir S. cerevisiae, die hoof wyngis, maar nie vir ander gis spesies, gegroepeer en bekend as nie-Saccharomyces giste, nie. Alhoewel, die laasgenoemde word al hoe meer gebruik in die industrie saam met S. cerevisiae en die voorkeur van hierdie giste moet ondersoek word om optimale fermentasie en produksie van aroma verbindings te verseker. Dit kan die potensieële kompetisie tussen gis spesies ontrafel en daarmee saam ook potensieële byvoegings behoeftes om staak fermentasies en produksie van nie-geurige aroma verbindings te verhoed. Hierdie studie ondersoek die stikstofbron voorkeur van ‘n aantal kommersiële nie-Saccharomyces giste (Pichia kluyveri Viniflora® FootZenTM, Torulaspora delbrueckii BiodivaTM TD291, Metschnikowia pulherrima Flavia® MP346 en Lanchancea thermotolerans Viniflora® ConcertoTM) deur reinkultuur fermentasies in sintetiese wynmedium met stikstofbronne by gelyke bruikbare stikstof konsentrasies te doen. Opname verskil tussen die verskillende gisspesies, alhoewel P.kluyveri en M.pulcherrima soortgelyke opname getoon het so ook het L. thermotolerans en T.delbrueckii. Stikstof opname was ook proporsioneel aan CO2 vrystelling, suiker verbruik en gisgroei. L.thermotolerans en T.delbrueckii het ‘n groter aantal stikstofbronne opgeneem as P.kluyverii en M.pulcherrima asook teen ‘n vinniger tempo. Verskille in die stikstofbron voorkeur is tussen die giste waargeneem. Die teenwoordigheid van stikstof het die % van aminosure wat opgeneem word tussen die verskillende giste beinvloed asook die begin van aminosuur opname deur T.delbrueckii. Opeenvolgende fermentasies van druiwesap met gelyke stikstof konsentrasies toon dat L.thermotelarns en T.delbrueckii in groter kompetisie is met S.cerevisiae as P.kluyveri en M.pulcherrima. Hierdie kompetisie word getoon in die fermentasie kinetika van opeenvolgende fermentasies asook die vlakke van aromaverbinding produksie. Dit wil voorstel dat opeenvolgende fermentasies met L.thermotolerans en T.delbrueckii hoër stikstofbron byvoegings mag benodig as fermentasies met P.kluyveri en M.pulcherrima, vir S.cerevisiae om die fermentasie te voltooi asook om die konsentrasie van voorkeur aroma verbindings te verhoog. Sommige ooreenkomste word gesien ivm die opname van stikstofbronne en die aroma verbindings geproduseer, byvoorbeeld die opname van treonien en die ooreenstemmende popanol produksie. Die data wys dat, na inkulasie met S. cerevisiae, die populasie van nie-Saccharomyces giste afneem en die selle moontlik outoliseer, waardeur stikstof bronne vrygestel en wat deur S.cerevisiae opgeneem kan word. Hierdie studie verbeter ons kennis van nie-Saccharomyces giste se stikstof voorkeure en bepaal skakels tussen stikstof bron opname en aroma verbinding produksie. Kompetisie tussen giste is en skakels met stikstof opname en fermentasie vermoë is ook bewys. | af_ZA |
| dc.format.extent | ix, 84 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/102925 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | e |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Yeast fungi -- Biotechnology | en_ZA |
| dc.subject | UCTD | |
| dc.subject | Non-saccharomyces yeasts | en_ZA |
| dc.subject | Wine and winemaking -- Biotechnology | en_ZA |
| dc.subject | Fermentation | en_ZA |
| dc.subject | Nitrogen in agriculture | en_ZA |
| dc.subject | Wine -- Flavor and odor | en_ZA |
| dc.title | The utilisation of nitrogenous compounds by commercial non-Saccharomyces yeasts associated with wine | en_ZA |
| dc.type | Thesis | en_ZA |