Saccharomyces cerevisiae cells were entrapped in 1% (w/w) alginate. The optimum flow rate and glucose concentration in the feed for maximum ethanol yield were 50 ml h(-1) and 50 g l(-1) respectively. Immobilized S. cerevisiae performed better with medium containing nutrients and 0.05 M CaCl2 (28 days) than with nutrients alone (10 days). Ethanol production decreased with an increase in alginate concentration. A packed bed reactor containing S. cerevisiae entrapped in 1.5% (w/w) alginate operated continuously for 40 days without problems and loss of productivity, when the glucose feed was supplemented with nutrients and calcium.