Article

High cell density ethanol fermentation in an upflow packed-bed cell recycle bioreactor

Biotechnology and Bioprocess Engineering (Impact Factor: 1.22). 04/2008; 13(2):123-135. DOI: 10.1007/s12257-008-0004-9

ABSTRACT An upflow packed-bed cell recycle bioreactor (IUPCRB) is proposed for obtaining a high cell density. The system is comprised
of a stirred tank bioreactor in which cells are retained partially by a packed-bed. A 1.3 cm (ID) × 48 cm long packed-bed
was installed inside a 2 L bioreactor (working volume 1 L). Continuous ethanol fermentation was carried out using a 100 g/L
glucose solution containing Saccharomyces cerevisiae (ATCC 24858). Cell retention characteristics were investigated by varying the void fraction (VF) of the packed bed by packing
it with particles of 0.8∼2.0 mm sized stone, cut hollow fiber pieces, ceramic, and activated carbon particles. The best results
were obtained using an activated carbon bed with a VF of 30∼35%. The IUPCRB yielded a maximum cell density of 87 g/L, an ethanol
concentration of 42 g/L, and a productivity of 21 g/L/h when a 0.5 h−1 dilution rate was used. A natural bleeding of cells from the filter bed occurred intermittently. This cell loss consisted
of an average of 5% of the cell concentration in the bioreactor when a high cell concentration (approximately 80 g/L) was
being maintained.

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