Development of continuous fermentation using immobilized yeast cells for wine cooler process development

Abstract

The continuous wine fermentation process, which employs a newly designed tapered column type bioreactor and immobilized yeast cells (Montrachet 522), was studied and its fermentation performance was compared with batch and suspended cell continuous wine fermentation systems.

It was found that a stable continuous culture fermentation process could be maintained for a period of 2–3 mo when the new bioreactor system packed with immobilized yeast cells was employed. The new bioreactor containing immobilized yeast cells performed significantly better than the suspended cell culture system or batch culture. The effluent wine from the continuous fermentor system contained 7.1% (v/v) ethanol and 0.18% (w/v) residual sugar at 0.01 h^-1 dilution rate. The new continuous bioreactor system also gave 17–34 times higher maximum ethanol productivity compared to the conventional batch wine fermentation. At a low dilution rate, 0.01^-1, as high as 92% sugar to ethanol yield was achieved.

Based on the results obtained from this study, the possibility of developing a continuous wine cooler fermentation process was demonstrated. A two-stage continuous wine fermentation system may be designed and operated. The grape juice can be fed into the first-stage that is operated at about 0.2 h^-1 dilution rate and the effluent from the first-stage is fed into the second-stage continuous fermentor operated at about 0.01 h^-1 dilution rate. By doing so, a wine cooler can be produced continuously and efficiently, by employing the newly designed tapered column type bioreactor charged with the immobilized yeast cells.