1. Introduction
Yeasts, both Saccharomyces and non-conventional strains, are currently the focus of active research due to their impressive applications in biotechnological bioprocesses, such as being hosts to produce recombinant proteins or main actors of the fermentation industries. Moreover, they are increasingly important tools in systems biology since they are used as simple models when studying the physiology or gene regulation of eukaryotic organisms.
2. An Overview of Published Articles
Ten papers, comprising two reviews and eight research papers, that represent recent developments in the above-mentioned fields have been published in this Special Issue. One of the reviews (Contribution 1) is a very nice description of the role that yeasts have played in history and their present applications in cancer research, with a focus on HMGB proteins.
The other review (Contribution 2) reports on the characteristics of non-Sacharomyces yeasts and their impact on wine fermentation, which contribute significantly to wine flavor and aroma and, therefore, consumer acceptance.
Additionally, related to enology, Contribution 3 concerns beta-glucosidase from the yeast Metschnikowia pulcherrima (isolated from the surface of grapes). This enzyme shows suitable characteristics to be used in wine fermentations to liberate aromatic compounds.
Only one research paper of this Special Issue is devoted to Saccharomyces cerevisiae (Contribution 4), specifically to the purification and biochemical characterization of the enzyme P5C reductase that catalyzes the last step in both proline synthesis and arginine catabolism.
Contributions 5 and 6 discuss the use of non-Saccharomyces yeasts in beer fermentations. The first contribution outlines brewing beers with zero or low ethanol content, and the second contribution discusses controlling Lambic beer fermentation.
Two articles are related to using Komagataella phaffi (previously Pichia pastoris) as a protagonist. K. phaffi is a promising cell factory, a good producer of recombinant peptides and proteins, and it can use methanol and glycerol as carbon sources. To improve this biotechnological application, Contribution 7 studies the effect of MPC1 gene deletion on lactic acid production, encoding a mitochondrial pyruvate carrier. Contribution 8 focuses on the effect of methionine on gene expression in a methanol-containing media.
Similarly, Contribution 9 describes the identification of strong promoters and the construction of hybrid promoters to increase heterologous protein production in glycerol-based bioprocesses by another biotechnologically relevant yeast, Yarrowia lipolytica. Glycerol is an interesting substrate since it is the major byproduct of biodiesel production.
Finally, with the objective of waste valorization, Contribution 10 reports on the use of carotenogenic yeasts of the genus Rhodotorula and Sporidiobolus for the processing of waste oils/fats and waste glycerol. The selected strains were able to metabolize substrates mixed with these components, yielding abundant biomass with a high carotenoid content.
3. Conclusions/Perspectives
Yeasts are the principal protagonists of biotechnological industries. Although Saccharomyces cerevisiae is considered “the yeast”, non-conventional yeasts have gained ground on Saccharomyces in recent years. This fact is reflected in the papers presented in this Special Issue. Overall, these papers show recent research advances in the use of yeasts for wine and beer fermentation, waste valorization, enzymes, and the production of recombinant proteins and carotenoids. There is still much to explore and improve concerning these topics that are of high social and economic relevance.
Acknowledgments
To the authors and reviewers for their excellent contributions to this Special Issue. To the Microorganisms Editorial Office for their professional assistance and continuous support.
Conflicts of Interest
The authors declare no conflicts of interest.
List of Contributions
- Lamas-Maceiras, M.; Vizoso-Vázquez, Á.; Barreiro-Alonso, A.; Cámara-Quílez, M.; Cerdán, M.E. Thanksgiving to Yeast, the HMGB Proteins History from Yeast to Cancer. Microorganisms 2023, 11, 993. https://doi.org/10.3390/microorganisms11040993.
- Maicas, S.; Mateo, J.J. The Life of Saccharomyces and Non-Saccharomyces Yeasts in Drinking Wine. Microorganisms 2023, 11, 1178. https://doi.org/10.3390/microorganisms11051178.
- Mateo, J.J. Physico-Chemical Characterization of an Exocellular Sugars Tolerant Β-Glucosidase from Grape Metschnikowia pulcherrima Isolates. Microorganisms 2023, 11, 964. https://doi.org/10.3390/microorganisms11040964.
- Forlani, G.; Sabbioni, G.; Ruszkowski, M. Functional Characterization of Saccharomyces cerevisiae P5C Reductase, the Enzyme at the Converging Point of Proline and Arginine Metabolism. Microorganisms 2022, 10, 2077. https://doi.org/10.3390/microorganisms10102077.
- Simões, J.; Coelho, E.; Magalhães, P.; Brandão, T.; Rodrigues, P.; Teixeira, J.A.; Domingues, L. Exploiting Non-Conventional Yeasts for Low-Alcohol Beer Production. Microorganisms 2023, 11, 316. https://doi.org/10.3390/microorganisms11020316.
- Postigo, V.; García, M.; Arroyo, T. Study of a First Approach to the Controlled Fermentation for Lambic Beer Production. Microorganisms 2023, 11, 1681. https://doi.org/10.3390/microorganisms11071681.
- de Oliveira Junqueira, A.C.; Moreira Melo, N.T.; Skorupa Parachin, N.; Costa Paes, H. Loss of a Functional Mitochondrial Pyruvate Carrier in Komagataella phaffii Does Not Improve Lactic Acid Production from Glycerol in Aerobic Cultivation. Microorganisms 2023, 11, 483. https://doi.org/10.3390/microorganisms11020483.
- Ianshina, T.; Sidorin, A.; Petrova, K.; Shubert, M.; Makeeva, A.; Sambuk, E.; Govdi, A.; Rumyantsev, A.; Padkina, M. Effect of Methionine on Gene Expression in Komagataella phaffii Cells. Microorganisms 2023, 11, 877. https://doi.org/10.3390/microorganisms11040877.
- Georgiadis, I.; Tsiligkaki, C.; Patavou, V.; Orfanidou, M.; Tsoureki, A.; Andreadelli, A.; Theodosiou, E.; Makris, A.M. Identification and Construction of Strong Promoters in Yarrowia lipolytica Suitable for Glycerol-Based Bioprocesses. Microorganisms 2023, 11, 1152. https://doi.org/10.3390/microorganisms11051152.
- Szotkowski, M.; Plhalová, Ž.; Sniegoňová, P.; Holub, J.; Chujanov, O.; Špačková, D.; Blažková, J.; Márová, I. Conversion of Mixed Waste Food Substrates by Carotenogenic Yeasts of Rhodotorula sp. Genus. Microorganisms 2023, 11, 1013. https://doi.org/10.3390/microorganisms11041013.
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