Monday, April 30, 2007

Bioethanol from germinated grains

Mette Hedegaard Thomsen1, Nobert Tajoacha2, Chen Wu2, Søren Hovgaard2, Lars P. Houmøller2, Jens Bo Holm-Nielsen2, and Anne Belinda Thomsen1. (1) Biosystems Department, Risoe National Laboratory, P.O. Box 49, 4000 Roskilde, Roskilde, Denmark, (2) ACABS, Aalborg University Esbjerg, Niels Bohrs vej 8, 6700 Esbjerg, Denmark

The most well-known way to produce bioethanol is by the enzymatic hydrolysis and fermentation of starch. In a new project “BioConcens” (2007) sponsored by DARCOF (DAnish Research Center for Organic Food and farming) one aim is to  develop a combined ethanol and biogas production for use in organic farming using starch containing biomass. Natural enzymes from cereals will be used for hydrolysis of starch to glucose in accordance with technology in brewing technology. Commercial enzymes are often produced from gene-modified organisms and will therefore not be used in the suggested organic context or process.

 A preliminary study was performed in which grains of wheat, rye, and barley were germinated using traditional methods applied in malting for beer production. During malting the amylase enzymes present in the grain are activated (autoamylolytic effect). Three steps were applied in the malting process; steeping, germination, and drying of the grains. After malting the grains were milled and mixed with water to 13% DM, cooked at 57.5°C for 2 hours (to activate the enzymes), and cooled to 30°C before adding Bakers Yeast.

 The results of this study indicate that efficient hydrolysis of starch can be achieved by activation of autoamylolytic enzymes in cereal grains after a malting process. The ethanol yields obtained in the autoamylolytic hydrolysis was comparable (or slightly higher) to that of reference experiments using commercial enzymes (amylases). The highest ethanol yield was obtained with wheat (0.34 g/g DM grain), followed by barley (0.31 g/g DM grain), and rye (0.29 g/g DM grain).