Furfural
Furfural is a compound that results from the production of juices and wines and as a byproduct in the degradation of biomass ([http://www.ncbi.nlm.nih.gov/pubmed/12000990|Boopathy, 2002] and [http://www.ncbi.nlm.nih.gov/pubmed/1929367|Rivard, 1991]). Furfural can contaminate the product streams of lignocellulose breakdown in production of sugar from biomass. This contaminant inhibits the fermentation of glucose, and thus prevents efficient formation of the product. Methanococcus sp. B can anaerobically degrade 2-methylfurfural and 5-methylfurfural to furfural and methane ([http://www.ncbi.nlm.nih.gov/pubmed/16535410|Boopathy, 1996]). Understanding biodegradation for this compound is important for remediation of paper mill and oatmeal processing effluents, as well as the development of renewable energy sources ([http://www.ncbi.nlm.nih.gov/pubmed/1929367|Rivard, 1991]). Some methanogenic bacteria can degrade furfural to methane and carbon dioxide. Desulfovibrio sp. F-1 anaerobically degrades furfural to acetate (not shown in pathway) ([http://www.ncbi.nlm.nih.gov/pubmed/16346423|Brune, 1983)]. Furfural can be converted by E. coli LYO1, yeast and methanogens to furfuroyl alcohol, which does not inhibit the production of glucose ([http://www.ncbi.nlm.nih.gov/pubmed/16535618|Belay et al., 1997] and [http://www.ncbi.nlm.nih.gov/pubmed/16111779|Gutierrez et al., 2006]). Oxidation of the alcohol yields furfural. Furfural is also degraded to 2-oxoglutaric acid (alpha keto-glutarate) via an activating CoA ester in Pseudomonas putida Fu1 ([http://www.ncbi.nlm.nih.gov/pubmed/16346423|Brune, 1983] and [http://www.ncbi.nlm.nih.gov/pubmed/1929367|Rivard, 1991]). Pseudomonas putida aerobically degrades furfural to produce 2-oxoglutarate. The aldehyde is oxidized to 2-furoate, and subsequent activation via the attachment of a CoA group results in hydroxylation. Tautomerization followed by a lactone hydrolysis results in 2-oxoglutarate ([http://www.ncbi.nlm.nih.gov/pubmed/2170335|Koenig et. al, 1990]).