Brazil gets a third of its fuel from sugarcane-based ethanol, and ethanol producers want to increase that figure by refining the fermentation process. Brazilian labs are exploring everything from the genetic engineering of yeast to new approaches to producing ethanol from agricultural waste. In research to be published next month in the American Chemical Society journal Biotechnology Progress, Brazilian researchers claim to have demonstrated a seemingly unlikely means to higher yields: magnetic fields.
The researchers at the University of Campinas, in Brazil, say that they boosted ethanol yield 17 percent and shaved two hours off of a 15-hour fermentation process simply by circulating the fermentation brew past six magnets, each about the size of an overstuffed wallet. “The fermentation time can be reduced, and consequently, the production cost can also be reduced,” says Victor Haber Perez, the University of Campinas food engineer who led the research team.
A slew of recent reports highlight the importance of cutting the cost of biofuel production and boosting yields. Earlier this month, for example, the Organisation for Economic Co-operation and Development warned that biofuels–as currently produced–will inflate food prices and are a relatively costly way to reduce petroleum imports and carbon-dioxide emissions. (See “The High Costs of Biofuels.”)
Looking to magnets for help isn’t as crazy as it sounds. In fact, magnetic-field effects on microbial and mammalian cells are well documented. Biologists now view magnetic-field “pollution” from mobile-phone towers as a likely cause of a decline in the population of some migratory birds that rely on magnetic fields for navigation. And genetic engineers are experimenting with magnetic fields as a tool to control the growth and differentiation of stem cells. However, magnetically enhanced fermentation is a more controversial idea. There have been relatively few studies of magnetic effects on yeast cells–particularly the yeast cells employed in fermentation–and the results have been contradictory.
In 2003, Brazilian researchers at the Federal University of Pernambuco, in Recife, created a stir with a report that a static magnetic field caused marked increases in the growth of yeast and the ethanol concentration in laboratory-scale fermentations that used Saccharomyces cerevisiae. (S. cerevisiae is the yeast most commonly used in the Brazilian biofuels industry to produce ethanol from sugarcane.) A year later, however, Spanish radiobiologists at the University of Malaga threw that work into doubt, reporting that they had observed no stimulation of S. cerevisiae when it was subjected to a (much weaker, admittedly) magnetic field. They also failed to observe any impact from the alternating magnetic fields used in some earlier studies.
Perez and his colleagues set out to settle the matter, using controlled experiments in a state-of-the-art industrial bioreactor. They diverted the fermentation mixture of sugarcane molasses and yeast out of the reactor via stainless-steel pipes that passed between six magnets with a combined field strength of 20 milliteslas–roughly halfway between the strengths of the magnets employed in previous tests. The results confirmed the 2003 report from the group in Recife: a static magnetic field increased the yeast’s rate of sugar metabolism and boosted ethanol production by 9 percent. The higher 17 percent increase was observed when Perez employed a solenoid–basically, a wire coil around the magnets–to alternate the 20-millitesla field.