Increased oxygen transfer in a yeast fermentation using a microbubble dispersion
Kaster, Jeffrey Allen
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The use of a microbubble dispersion (MBD) for oxygen transport in a yeast fermentation was studied. No surfactants were added to the fermentations; the microbubbles were formed using only the surfactants naturally produced by the yeast. The growth rate of a Saccharomyces cerevisiae culture was found to be almost twice as great for a microbubble dispersion sparged fermentation, as for a gas sparged fermentation when equivalent volumes of air or microbubble dispersion were used. The growth rate of the MBD sparged fermentation was 0.108/hr, as opposed to 0.068/hr for the air sparged fermentation. Oxygen transfer rates were measured by the yield coefficient, dynamic, and direct methods. The oxygen transfer coefficient was found to be approximately 190/hr and independent of the fermenter impeller speed, over the range of 100 - 580 RPM, for the micro bubble dispersion fermentation. Over the same range, the oxygen transfer coefficient for the air sparged fermentation rose from 55 to 132/hr. The power requirements for the fermenter systems were estimated. It was determined that a five fold reduction in the fermenter to MBD generator volume ratio could be made.
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