Strain diversity in Saccharomyces cerevisiae thiamine production capacity

Vitamin B₁ , also known as thiamine, is an important vitamin that, besides its role in human health, is converted to meat aromas upon exposure to high temperatures. Therefore, it is relevant for the production of vegan meat-like flavours. In this study, we investigated 48 Saccharomyces cerevisiae strains for their thiamine production capacity by measuring the intracellular and extracellular vitamins produced in the thiamine-free minimal medium after 72 h of growth. We found approximately an 8.2-fold difference in overall thiamine yield between the highest and lowest-producing strains. While the highest thiamine yield was 254.6 nmol/L, the highest thiamine-specific productivity was 160.9 nmol/g DW. To assess whether extracellular thiamine was due to leakage caused by cell damage, we monitored membrane permeabilization using propidium iodide (PI) staining and flow cytometry. We found a good correlation between the percentage of extracellular thiamine and PI-stained cells (Spearman's ρ = 0.85). Finally, we compared S. cerevisiae CEN.PK113-7D (wild type [WT]) to three strains evolved in a thiamine-free medium for their thiamine production capacity. On average, we saw an increase in the amount of thiamine produced. One of the evolved strains had a 49% increase in intracellular thiamine-specific productivity and a biomass increase of 20% compared with the WT. This led to a total increase in thiamine yield of 60% in this strain, reaching 208 nmol/L. This study demonstrated that it is possible to achieve thiamine overproduction in S. cerevisiae via strain selection and adaptive laboratory evolution.