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| Author(s): |
Carla Inês Soares Rodrigues
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos |
| Defense date: | 2021-05-10 |
| Examining board members: |
Andreas Karoly Gombert;
Patricia Osseweijer;
Paola Branduardi;
Elizabeth Bilsland;
Christoph Herwig;
Pascale Daran Lapujade
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| Advisor: | Andreas Karoly Gombert |
| Abstract | |
Industrial sucrose-based fermentations are feasible to a great extent due to the yeast Saccharomyces cerevisiae’s natural ability to metabolize this sugar at high rates. However, our current understanding on sucrose metabolism in this yeast, in particular the knowledge gained using well-controlled cultivation conditions, is extremely limited. The hitherto reported studies focused on one laboratory strain or on strains that were pre-adapted to growth on sucrose for several generations, which changed the strain’s original physiology. The main focus of this thesis was a quantitative aerobic physiological study using the S. cerevisiae CEN.PK113-7D, JP1, and UFMG-CM-Y259 strains during growth on sucrose as sole carbon and energy source, with a subsequent comparative analysis of the untargeted global proteome using growth on glucose as reference. The three studied strains displayed different growth capacity on sucrose during batch bioreactor cultivations, and this was accompanied by distinct extracellular hexose concentration and invertase activity profiles. These observations suggest that under the evaluated conditions invertase activity was a constraint for sucrose metabolism in the laboratory strain CEN.PK113-7D. Furthermore, cultivations with glucose or fructose alone, or in an equimolar mixture, were performed. These experiments enabled comparative physiological analyses that indicated combined mechanisms of sucrose utilization by the industrial strain JP1, and exposed the ability of the indigenous strain UFMG-CM-Y259 to grow faster on sucrose than on glucose under well-controlled conditions. Besides, for the latter strain, the physiology on fructose was shown to be more similar to that on sucrose than on glucose. A label free quantification technique was employed to reveal the changes in protein abundance for the sucrose-glucose pairwise comparisons. The abundance of invertase (Suc2p) was shown to be significantly unchanged in all strains. Besides, no changes in transcription factor (TF) levels were common to the three strains, which indicates that no protein in this category responded exclusively to sucrose levels. The protein kinase A (PKA) regulatory subunit, Bcy1p, was up- and down-regulated in CEN.PK113-7D and UFMG-CM-Y259, respectively, suggesting that PKA influences the growth capability on sucrose. At last, an inverse pattern of overrepresented GO biological processes and enriched KEGG pathways was shown for the CEN.PK113-7D and UFMG-CM-Y259 strains. Specially, an inverse correlation between growth rate on sucrose and ribosome enrichment was observed, which corroborates a previous theory on a trade-off between ATP yield per protein mass and the respiratory capacity. According to this theory, higher respiratory capacity demands more ribosomes, and, therefore, lower ATP yield per protein mass is achieved by the cells, which has consequences on ?MAX. This study demonstrates the potential for improving sucrose-based industrial bioprocesses using S. cerevisiae as a cell factory. Additionally, the knowledge acquired with the work reported in this thesis provides the basis for further research on strain improvement (AU) | |
| FAPESP's process: | 16/07285-9 - Why does not Saccharomyces cerevisiae grow faster on glucose than on sucrose? |
| Grantee: | Carla Ines Soares Rodrigues |
| Support Opportunities: | Scholarships in Brazil - Doctorate |