Biotechnologie, Agronomie, Société et Environnement (Jan 2010)
Bioconversion of potatoes residues or surplus potatoes to ethanol under non axenic conditions [abstract]
Abstract
Biofuels can offer an alternative to fossil fuels in the context of climate change and fossil reserves depletion. With 3 million tons of potatoes produced in 2007 and a high yield per hectare of 47 tons, Belgium is the 19th largest producer in the world. The residual and surplus potatoes could be used to produce bioethanol by fermentation. We examined the feasibility of a simple ethanol fermentation process under non axenic conditions. The substrate was pretreated with commercial amylases or by adding as low as 10% FM (Fresh Matter) barley malt. It was then fermented with Saccharomyces cerevisiae. Ethanol and volatile fatty acids were analyzed by GC-FID and soluble sugars were analyzed with the Anthrone method. Starch from potatoes was hydrolyzed to soluble sugars. Hydrolysis seems to continue with 10% FM of barley malt after 48 h while the hydrolysis stopped or decelerated with commercial enzymes. With 10% FM of malt, 3 h of hydrolysis and 7 days of fermentation, an ethanol concentration of 42 g.l-1 was obtained and the conversion yield was 139 gethanol.kg-1 DM. The fermentation conversion yield of soluble sugars to ethanol was > 82% and the endogenous competition was limited. However, starch hydrolyzing seems to be a limiting step under the conditions tested. Commercial enzymes did not provide better results under the same conditions.
