Accelerated evolution of lager yeast strains for improved flavour profiles

Fermented food and beverages have accompanied humans throughout history. Several species of microorganisms can transform raw materials into products with different and improved characteristics, for example alcoholic beverages (wine and beer) or dairy products, such as yogurt. In a world of constant change and competitiveness, brewers have to modulate and create new products to satisfy consumers. Therefore, the aim of my project is to generate lager yeast capable of producing molecules that improve the organoleptic profile of alcoholic beverages and understand the genetic and biochemical changes that increases the production of these aromatic molecules. The initial work has focused on the Ehrlich Pathway and the ester production. To produce changes in the genome, two approaches have been followed: one chemical way, using Radicicol, and one physical way, Heat Shock Thermal Stress (HSTS). Both ways inhibit Heat Shock proteins. Furthermore, this inhibition produces DNA damage, introducing Single sStrand Breaks (SSBs) and Double Strand Breaks (DSBs). The result of this inhbition is damage in the DNA and, furthermore, mutations in the DNA (aneuplidies and INDELS). After the Accelerated evolution, the evolved strains were plated on media containing amino acid analogues. These amino acid analogues select for cells with decreased feed-back inhibition of amino acid biosynthesis. Different mutant strains were generated with these two ways. These strains will be tested by different approaches, as growth curves, genome ploidy using cCGH and CHEF gel and qPCR analysis to measure the flux throughout the fermentation.