Physical contact in oenological yeast-bacteria interactions
| dc.contributor.advisor | Bauer, Florian | en_ZA |
| dc.contributor.author | Petzsch, Irmela | en_ZA |
| dc.date.accessioned | 2022-03-10T19:37:35Z | |
| dc.date.available | 2022-04-29T09:00:16Z | |
| dc.date.available | 2023-03-31T03:00:12Z | |
| dc.date.issued | 2022-03 | |
| dc.description | Viticulture and Oenology | en_ZA |
| dc.description.abstract | Yeast-bacteria interactions are of special interest in wine, as these species are responsible for specific fermentative processes and their interactions have downstream effects on the end-product. Typically, these organisms interact through direct (cell-cell) or indirect (metabolic) contact, but limited information is available on the specific mechanisms behind such interactions. Research has focused largely on yeast, thus the role of physical contact in yeast-bacteria interactions remains unclear. One tool to study such interactions is a multi-membrane bioreactor (MMB). This enables the physical separation of cells while maintaining them in the same growth media. This study was designed to optimize a novel MMB to investigate the effect of physical contact in interactions between Saccharomyces cerevisiae yeast and Lactiplantibacillus plantarum bacteria. Additionally, it expands upon previous research where bacterial isolates were exposed to yeast as biotic selection pressures in a directed evolution experiment. Isolates from this experiment were investigated in this study and phenotypes compared to the parental bacteria, to gain insight into evolutionary aspects. The research methodology centred around selecting pairs of strains displaying phenotypes of interest from small-scale yeast-bacteria fermentations, to be further studied in the optimized MMB. Initial small-scale experiments displayed a variety of phenotypes of the evolved bacterial isolates, but most interestingly, some of the evolved isolates displayed an ability to limit yeast growth compared to the parental bacteria strain. These results are aligned with the selection strategy and suggests the success of biotic selection pressures in directed evolution. Based on the data, an isolate of interest, E59, was selected for further investigation in the MMB. Optimizing the MMB entailed performing a variety of experiments to mitigate issues like membrane fouling and ensure cells were successfully filtered. Once the successful growth of both microbial species was achieved over a 24-hour period, yeast and bacteria were investigated in both direct and indirect contact. MMB experiments revealed that physical contact likely plays a significant role in yeast-bacteria interactions. Direct contact improved bacterial growth, while it limited yeast growth compared to indirect contact. This was a major finding from this research. Once again, the effect of directed evolution was highlighted as E59 displayed less fluctuation in its effect on yeast compared to its parent, when contact types were changed. The MMB system was successfully optimized for yeast-bacteria interactions. This research provides relevant insights into both interactions between Lb. plantarum and S. cerevisiae, and the role of physical contact in yeast-bacteria interactions. It also provides a basis for further study of yeast-bacteria interactions in an optimized MMB, with which contact and genetic mechanisms can be investigated. | en_ZA |
| dc.description.abstract | Gis-bakterieë interaksies is van belang in wyn, omdat hierdie spesies verantwoordelik is vir spesifieke fermentasie prosesse en hulle interaksies die eindproduk beïnvloed. Hierdie organismes is tipies in direkte (sel-sel) of indirekte (metaboliese) kontak, maar beperkte informasie oor die spesifieke meganismes in beheer van sulke interaksies is beskikbaar. Navorsing het tot dusver hoofsaaklik op gis gefokus, dus bly die rol van fisiese kontak in gis-bakterieë interaksies onduidelik. Een metode om sulke interaksies te bestudeer is met ‘n multi-membraan bioreaktor (MMB). Dit maak die fisiese skeiding van selle moontlik, terwyl hulle in dieselfde groei medium onderhou word. Hierdie studie is ontwerp om ‘n nuwe MMB te optimaliseer, om die effek van fisiese kontak in interaksies tussen Saccharomyces cerevisiae gis en Lactiplantibacillus plantarum bakterieë te ondersoek. Verder, volg dit op navorsing waar bakterieë isolate aan gis bloot gestel is as biotiese seleksie druk in ‘n gerigte evolusie eksperiment. Isolate uit hierdie eksperiment is verder ondersoek in hierdie studie en fenotipes vergelyk met die oorspronklike, of ‘ouer ras’, bakterieë, om insig te kry in evolusionêre aspekte rakende bioties-gerigte evolusie. Die navorsingsmetodologie het begin deur die seleksie van stam-pare wat fenotipes van belang gewys het in kleinskaal gis-bakterieë fermentasies. Hierdie pare sou dan verder ondersoek word in die geoptimaliseerde MMB. Aanvanklike kleinskaal eksperimente het verskeie fenotipes getoon vir die ge-evoleerde bakterieë isolate. Die mees interessant resultaat was egter dat van die isolate, in vergelyking met hul ouerras, ‘n vermoë gewys het om gis groei te beperk. Hierdie resultate was in lyn met die seleksie strategie en stel die sukses van biotiese seleksie druk/ke in gerigte evolusie, voor. Gebasseer op die data, is ‘n isolaat van belang, E59, gekies vir verdere ondersoek in die MMB. Die optimalisering van die MMB het verskeie eksperimente behels, om probleme soos membraanvervuiling te beperk en te verseker dat selle suksesvol filtreer is. Sodra die suksesvolle groei van beide spesies oor 24-uur bereik is, is gis en bakterieë in direkte en indirekte kontak ondersoek. MMB eksperimente het gewys dat fisiese kontak ‘n betekenisvolle rol in gis-bakterieë interaksies speel. In vergelyking met indirekte kontak, het direkte kontak bakterieë se groei verbeter, terwyl dit gis groei beperk het. Hierdie uitkoms was ‘n groot bevinding vanuit ‘n navorsingsoogpunt. Weereens is die effek van gerigte evolusie uitgelig deur die variasie in die bakterieë se effek op gis tussen kontak tipes. E59 het minder variasie as die ouer getoon tussen kontak tipes. Die MMB sisteem is suksesvol geoptimaliseer vir gis-bakterieë interaksies. Hierdie navorsing bied relevante insigte in beide interaksie tussen Lb. plantarum en S. cerevisiae, asook die rol van fisiese kontak in gis-bakterieë interaksies. Dit bied ook ‘n basis vir verdere studie van gis-bakterieë interaksies in ‘n geoptimaliseerde MMB, waarmee kontak en genetiese meganismes ondersoek kan word. | af_ZA |
| dc.embargo.terms | 2023-03-31 | |
| dc.identifier.uri | http://hdl.handle.net/10019.1/124489 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.subject | Yeast | en_ZA |
| dc.subject | Bacteria; Membranes; Bioreactor; Evolution | en_ZA |
| dc.title | Physical contact in oenological yeast-bacteria interactions | en_ZA |
| dc.type | Thesis | en_ZA |