ETHANOL FERMENTATION IN A TOWER FERMENTER USING SELF-AGGREGATING SACCHAROMYCES-UVARUM - BIOREACTOR PERFORMANCE

A self-aggregating strain of Saccharomyces uvarum (U4) was used as a b iocatalyst to carry out continuous ethanol fermentation in a tower fer menter equipped with a cell separator. Cell aggregates (2-3 mm) formed a stable packed bed in the fermenter, and the cell separator retained yeast cells effectively. Corn steep liquor was used as a nitrogen sou rce for the fermentation of corn. syrup and black strap molasses. An e thanol productivity of 54 g/L/h was reached using corn syrup at a dilu tion rate of 0.7/h, and sugar concentration in the feed was 15% (w/v). For molasses fermentation, an ethanol productivity of 22 g/L/h was ob tained at a dilution rate of 0.7/h, and sugar concentration in the fee d was 12.5% (w/v). Ethanol yields obtained from tower fermentation are higher than those obtained from flask fermentation (96% for corn syru p fermentation and 92% for molasses fermentation). No significant loss in fermentation activity was observed after 3 mo of operation.