(94j) Initial Characterization of Furfural Resistant Derivatives of an Ethanologenic Strain of Escherichia Coli

Using bioethanol as an alternative fuel source has presented challenges in the development of various feedstocks for microbial fermentation. Corn stover provides a relatively economical process as it is a cheap raw material. To use corn stover, a complex pretreatment is required to release the necessary sugars from the hemicellulose. However, this pretreatment also produces toxic byproducts. One of the most important of these is the aldehyde furfural, which is toxic in its own right but also enhances the toxicity of other compounds produced during pretreatment, thus impacting the overall ethanol yield. As a consequence, corn stover pretreatment must also entail an overliming stage to reduce the concentration of furfural.

We have isolated a collection of furfural resistant derivatives of the ethanologenic strain Escherichia coli FBR5. Two major transformative mechanisms of furfural resistance have been observed in microorganisms. The first of these converts fufural to furic acid and requires aerobic conditions. The second mechanism, the conversion to furfuryl alcohol, can occur under anaerobic conditions. The initial characterization of our E. coli strains included furfural challenges during batch culture growth curves in aerated liquid media. The results of these experiments reveal that some of the strains exhibit strong resistance to furfural in both liquid culture and plate assays. Interestingly, other strains only display resistance in plate assays. Further studies such as HPLC on spent media and Microtox (Strategic Diagnostics; Newark, DE) testing are planned in order to better understand furfural resistance in the collection.

We have also begun pilot fermenter studies with our strains using synthetic media containing xylose and furfural. Preliminary results with furfural resistant strain PS6 show that it exhibits faster growth and ethanol production than the FBR5 parent. The development of the furfural tolerant strains raises the possibility of producing ethanol more economically as they may permit foregoing the overliming step during corn stover pretreatment.