Fakultetsopponent: Professor Isabel Sa-Correia, iBB - Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Portugal
Handledare: Docent Yvonne Nygård, Chalmers
Examinator: Professor Lisbeth Olsson, Chalmers
The transition towards a greener society that is less reliant on petroleum, is a central priority for mankind survival. Genetically modified yeasts can nowadays be used to produce a wide spectrum of chemicals and therefore represent a competitive alternative to fossil-based production. An advantage with yeasts is that they can grow on agricultural and forestry residual products to produce various useful chemicals. However, the residual products need to be pretreated to release energy (sugars) that yeasts can use. This unfortunately releases toxic compounds which hamper yeast productivity.
In this thesis I investigate how yeast reacts to the stress caused by these toxic compounds. First, I explore how different yeasts respond to being cultivated on a specific forestry residual product, previously pretreated. Then, I focus on two of the most abundant inhibitors found in the forestry residual products after the pretreatments: acetic acid and formic acid. For this, I developed and used a novel biological tool for acetic acid sensing, which allows to detect and report the acetic acid produced or accumulated inside the cells. I also analyzed genes that are involved in yeast adaptation to acetic and formic acid. Altogether, this thesis provides crucial insights into yeast responses to stress that is present in yeast-based biorefineries. This knowledge can be used to develop modified yeasts with improved performances and tolerance, thus contributing to a greener industrial production.