O-9
The analysis of ergosterol concentration in yeast: Its influence on fermentation
Presenter: Masahiro Gomi, Kirin Brewery Co Ltd, Yokohama, Japan
Co-Authors: Takeo Imai, Yutaka Ogawa, and Motoo Ohkochi, Kirin Brewery Co Ltd, Yokohama, Japan

Ergosterol is an essential component in yeast cells because it must be contained in yeast intercellular membrane. Besides, it is widely known that ergsterol is synthesized only under the conditions that there exists oxygen around yeast to be converted from its precursors. Therefore, in addition to intercellular pH, it will be expected to be an important indicator to predict yeast vitality and fermentation performance by means of the determination of its concentration in yeast. Some groups have already reported its concentration at the end of fermentation and its growth-limiting level (0.1%). There are some methods to measure ergsterol concentration in yeast cells. In general, it is extracted from lyophilized yeast cells and then determined. There are mainly two methods to analyze ergosterol; one is the colorimetric method with acetic anhydride and sulfuric acid (Liebermann-Burchard reaction) and the other is the HPLC, high-pressure liquid chromatography, method with reversed-phased columns and UV detection. The former is so unstable that the reaction time must be exactly controlled. Otherwise, we do not have precise results. On the contrary, the latter is more useful and has been used for the measurement of ergosterol concentration in a variety of environmental matrices. Accordingly, we have analyzed ergosterol concentration in yeast cells and we can have some interesting information by means of the modified ergosterol determination method with HPLC system. This method gives us the improved recovery rate and reproducibility. We could also show some results that indicate that ergosterol is related with yeast vitality and its proper level for the fermentation.

Masahiro Gomi received a M.Sci. in biological chemistry from Tokyo University in Tokyo, Japan. He began employment with Kirin Brewery Co., Ltd. in April 1989. He worked at malting and brewing plants and also quality management section at headquarters from 1989 to 2000. Since January 2001, he has been at Research Laboratory for Brewing to improve malt and beer quality.