Magnetic effects induced in ethanolic fermentation by Saccharomyces cerevisiae strain DAUFPE-1012 were studied during a 24 h exposure to 220 mT steady magnetic fields (SMF) at 23 +/- 1 degrees C, produced by NdFeB rod magnets. The magnets were attached diametrically opposed (N to S) to a cylindrical tube reactor. The biomass growth in the reactor culture media (yeast extract + glucose 2%) during 24 h was monitored by measurements of optical density, which was correlated to cell dry weight. Ethanol concentration and glucose level were measured every 2 h. The pH of the culture media was maintained between 4 and 5. As a result, biomass (g/L) increased 2.5-fold and ethanol concentration 3.4-fold in magnetized cultures (n = 8) as compared with SMF nonexposed cultures (n = 8). Glucose consumption was higher in magnetized cultures, which correlated to the ethanol yield.