Metabolite production by some strains of industrial yeasts in various phases of cell growth

Presented bachelor thesis is focused on industrial application of chosen yeast strains. Principal interest of work is to study production of primary and secondary metabolites during individual growth phases. Optimal growth conditions as well as influence of exogenous stress factors (mainly oxidative and/or salt stress) on cell growth and yeast metabolism are discussed. In experimental part growth curve of industrial strain Phaffia rhodozyma was determined. Biomass increase (maximum in 90th hour 5,441 g/l), astaxanthin production (secondary metabolite) and/or ergosterol biosynthesis (primary metabolite) were observed. The best ration of astaxanthin to total carotenoids was 50 %. Next studied metabolite was ergosterol, its total amount in dry biomass was 0.11 %. In conclusion astaxanthin amounts produced in optimal growth conditions were compared with yields obtained under stress cultivations. Results of stress experiments illustrate positive influence of stress factors on cell growth as well as on astaxanthin biosynthesis. Low concentration of salt (2% NaCl) added in inoculum with 5 mM hydrogen peroxide in production medium would be the best combination in industrial applications