PROCESS TECHNOLOGIES FOR PRODUCING BIOFUELS AND COPRODUCTS FROM LIGNOCELLULOSIC FEEDSTOCKS
Location: Bioenergy Research Unit
Title: Butanol productivity enhancers in wheat straw hydrolyzate: employing potential of enhanced reaction rate
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 5, 2011
Publication Date: May 5, 2011
Citation: Qureshi, N., Bowman, M.J., Hector, R.E., Saha, B.C., Cotta, M.A. 2011. Butanol productivity enhancers in wheat straw hydrolyzate: employing potential of enhanced reaction rate [abstract]. In: Proceedings of the 33rd Symposium on Biotechnology for Fuels and Chemicals, May 2-5, 2011, Seattle, Washington. Paper No. 11-11.
Butanol production by fermentation is gaining momentum due to increased prices of fossil fuels. This 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. Furfural and HMF are sugar degradation products that were generated during wheat straw pretreatment using dilute sulfuric acid at 121 deg C. It is interesting that these chemicals are inhibitors to ethanol fermentation, while beneficial for butanol production using C. beijerinckii P260. An increase in productivity and product concentration of this magnitude would benefit commercial production of butanol from WSH.