Phenotypic landscape of non-conventional yeast species for different stress tolerance traits desirable in bioethanol fermentation
Artikel i vetenskaplig tidskrift, 2017

Background
Non-conventional yeasts present a huge, yet barely exploited, resource of yeast biodiversity for industrial applications. This presents a great opportunity to explore alternative ethanol-fermenting yeasts that are more adapted to some of the stress factors present in the harsh environmental conditions in second-generation (2G) bioethanol fermentation. Extremely tolerant yeast species are interesting candidates to investigate the underlying tolerance mechanisms and to identify genes that when transferred to existing industrial strains could help to design more stress-tolerant cell factories. For this purpose, we performed a high-throughput phenotypic evaluation of a large collection of non-conventional yeast species to identify the tolerance limits of the different yeast species for desirable stress tolerance traits in 2G bioethanol production. Next, 12 multi-tolerant strains were selected and used in fermentations under different stressful conditions. Five strains out of which, showing desirable fermentation characteristics, were then evaluated in small-scale, semi-anaerobic fermentations with lignocellulose hydrolysates.

Results
Our results revealed the phenotypic landscape of many non-conventional yeast species which have not been previously characterized for tolerance to stress conditions relevant for bioethanol production. This has identified for each stress condition evaluated several extremely tolerant non-Saccharomyces yeasts. It also revealed multi-tolerance in several yeast species, which makes those species good candidates to investigate the molecular basis of a robust general stress tolerance. The results showed that some non-conventional yeast species have similar or even better fermentation efficiency compared to S. cerevisiae in the presence of certain stressful conditions.

Conclusion
Prior to this study, our knowledge on extreme stress-tolerant phenotypes in non-conventional yeasts was limited to only few species. Our work has now revealed in a systematic way the potential of non-Saccharomycesspecies to emerge either as alternative host species or as a source of valuable genetic information for construction of more robust industrial S. serevisiae bioethanol production yeasts. Striking examples include yeast species like Pichia kudriavzevii and Wickerhamomyces anomalusthat show very high tolerance to diverse stress factors. This large-scale phenotypic analysis has yielded a detailed database useful as a resource for future studies to understand and benefit from the molecular mechanisms underlying the extreme phenotypes of non-conventional yeast species.

Non-Saccharomyces,

Fermentation,

Bioethanol

Yeasts,

Stress tolerance,

Phenotype,

Författare

Vaskar Mukherjee

KU Leuven

VIB

Dorota Radecka

VIB

KU Leuven

Guido Aerts

KU Leuven

Kevin J. Verstrepen

KU Leuven

VIB

Bart Lievens

KU Leuven

Johan M. Thevelein

VIB

KU Leuven

Biotechnology for Biofuels

1754-6834 (eISSN)

Vol. 10 216

Ämneskategorier

Industriell bioteknik

Biokemi och molekylärbiologi

Bioprocessteknik

Mikrobiologi

Genetik

Styrkeområden

Livsvetenskaper och teknik (2010-2018)

DOI

10.1186/s13068-017-0899-5

Mer information

Skapat

2019-09-30