Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Butanol biofuel is a major product of acetone-butanol-ethanol (ABE) fermentation that can be produced from hydrolyzed agricultural residues and/or corn. A control glucose (60 g/L) based batch fermentation using Clostridium beijerinckii P260 resulted in an ABE concentration of 21.09 g/L with a productivity of 0.29 g/L·h. In our recent studies on bioconversion of wheat straw hydrolyzate (WSH) to butanol, the rate of fermentation was enhanced by a factor of two or more as compared to glucose based control experiments. In the WSH fed bioreactor, ABE productivity and concentration were 0.60 g/L·h and 25.00 g/L, respectively. As a result of this increase in productivity (or fermentation rate), it was speculated that WSH contains one or more chemicals that enhance the rate of fermentation. For this reason, investigations were made to identify the chemical(s) responsible for increased productivity. WSH was extracted using methyl-tert butyl ether (MTBE), and the resulting extracted fraction was added to glucose based medium followed by fermentation. In presence of the extract (0.5 g/L), the rate of fermentation was observed to be 0.60 g/L·h with an ABE concentration of 24.98 g/L. These parameters are in agreement with WSH fermentation parameters. In a series of separate experiments, it was determined that hydroxymethyl furfural (HMF) present in WSH was responsible for this increase in productivity and product concentration. Furthermore, supplementation of furfural (0.5 g/L) to glucose based medium improved the rate of fermentation to 0.88 g/L·h. Interestingly, furfural and HMF are beneficial for butanol production using C. beijerinckii P260.