Enhanced high fructose syrup production by a hybrid fermentation/pervaporation system using a silicone rubber hollow fiber membrane module

Abstract

In this study, a new mutant of Saccharomyces cerevisiae was used for the co-production of fructose and ethanol by selectively converting glucose to ethanol from a sucrose medium. To enhance the fermentation process, a pervaporation unit was coupled to the bioreactor to keep the ethanol concentration in the broth at a low level, thereby reducing the ethanol inhibition on the yeast. The membrane module consisted of silicone rubber hollow fibers assembled in an inside feed/outside vacuum design. Batch fermentation, using a synthetic medium with 31% (w/v) sucrose, without membrane separation of ethanol required about 27 hr for the glucose concentration to decrease to 2% (w/v), with a fructose yield of 99%, and an ethanol yield of 78%. Batch fermentation, using the same medium, with membrane separation of ethanol required about 16.5 hr for the glucose concentration to reach the 2% (w/v) level, with a fructose yield of 96.5% and an ethanol yield of 79.5%, if the membrane was initiated 6 hr after the beginning of batch mode. In fed-batch mode, the yeast was able to process the equivalent of a 41% (w/v) sucrose feed in 24 hr, compared to over 40 hr without ethanol removal, with fructose and ethanol yields of 98 and 82%, respectively.

Acknowledgments