Wednesday, May 2, 2007 - 1:30 PM

Optimal biobutanol production from wheat straw

Ana M. López-Contreras, Robert R. Bakker, Maria Carvalho, and Pieternel A.M. Claassen. Agrotechnology and Food Sciences Group, Wageningen University and Research Centre, Bornsesteeg 59, Wageningen, Netherlands

As a result of the current policies on reduction of CO2 emissions and increasing energy security, new technologies to ensure sufficient supply of diesel-compatible biofuels from cheap biomass are needed. The acetone- butanol- ethanol (ABE) fermentation process can make a major contribution to reach this goal, since butanol represents an interesting precursor for diesel-fuel additives and other platform chemicals.
Wheat straw is one of the lignocellulosics with highest potential as substrate for bioethanol production, and its treatment for this purpose is being widely studied. However, its use as substrate for the ABE fermentation needs to be investigated.

Whitin a larger project investigating ABE fermentation, a number of pre-treatment techniques (chemical, mechanical) have been applied to wheat straw prior to hydrolysis with commercial cellulases for the production of hydrolysates. After chemical analysis of sugars, organic acids and potential fermentation inhibitors (Furfural, Hydroxymethyl furfural), the hydrolysates were used as fermentation media for Clostridium acetobutylicum and Clostridium beijerinckii strains for the production of ABE. The fermentations have been followed and relevant metabolites have been determined. Furthermore, medium optimisation studies have been carried out with relevant hydrolysates in order to formulate a medium in which maximal butanol yields and productivity can be reached. Such a straw hydrolysate-based fermentation medium may be used for an efficient industrial Biobutanol process. We have observed that the fermentability of wheat straw hydrolysates depends not only on the pre-treatment and hydrolysis conditions, but also on the properties and requirements of the specific organism to be used for fermentation.

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