STUDY OF INCREASING THE PRODUCTION OF VOLATILE FLAVOR COMPOUNDS BY THE YEAST Kluyveromyces marxianus THROUGH OPTIMIZATION OF CARBON AND NITROGEN SOURCES

Özet

The regulation of growth and the production of flavor compounds by Kluyveromyces marxianus were accomplished according to the nutritional requirements (yeast extract, ammonium sulphate and glucose concentrations) by using Response Surface Methodology experiments. Results proved that increasing both initial yeast extract (YE) and glucose concentrations in the fermentation medium favored both the growth and production of fusel alcohols. The major fusel alcohol (isoamyl alcohol) and the acetate ester compound (ethyl acetate) produced in all flasks were determined in the concentration range 1299-3996 µg L-1 and 1558 to 3122 µg L-1, respectively. In a scale-up attempt, productions were accomplished in a 5 L stirred tank bioreactor. The highest productivity values for major volatile flavor compounds, i.e., ethyl acetate (fruity), isoamyl alcohol (banana), 2-phenylethyl acetate (floral) were obtained during the exponential growth of the yeast in a 5 L stirred tank bioreactor. Additionally, the descriptive sensory terms “sourdough”, “flower” and “sweet aromatic” were characteristics for volatile compounds produced by K. marxianus. This work also demonstrated high product losses due to the stripping effect when the production scaled up from flasks to bioreactor.