An NADH-Coupled Biosensor for Engineering Redox Metabolism in Saccharomyces cerevisiae

Sammanfattning: Popular Abstract in English The work described in this thesis is in the field of industrial biotechnology, which can be defined as a branch of biotechnology aimed at sustainable production of chemicals, materials and fuels with the help of microorganisms. Microorganisms are very diverse and possess a wide variety of enzymes allowing them to transform inexpensive molecules into valuable ones, or toxic ones into non-toxic ones. However, most microorganisms are not naturally equipped to mass produce specific, valuable compounds. During recent decades, massive investments have therefore been made in designing and engineering organisms, thus transforming the cells into small factories, for large-scale production. A common obstacle is the production of side-products or by-products. These are produced naturally by the cell in response to the environmental conditions, and they lower the yields of the desired primary products. Therefore, if their production could be monitored or measured it would be easier to avoid them, increasing the primary yield and reducing the cost of the final product. In this work I have studied different process related cell properties of baker’s yeast, also known as Saccharomyces cerevisiae, one of the most widely established microbial production organisms. Some of its properties have been exploited for thousands of years, for example, in beer and bread making, but many more applications have been developed in the past century, such as the production of insulin and bioplastics. In my studies, I evaluated how yeast can be optimized to become a more efficient cellular factory for the production of various types of chemicals. In particular, I developed tools for monitoring the cells’ metabolic mode and their need to produce side-products. These efforts resulted in a novel sensor, enabling easier monitoring of the metabolic mode of the cells. This sensor also pointed to the potential of a well-known promoter for the production of user-defined metabolites, and showed promising for use in the search for new enzymes. Additionally I studied how the side-products can be replaced with more valuable chemicals, such as chiral alcohols and amines that can be used as active pharmaceutical ingredients.