PROCESS TECHNOLOGIES FOR PRODUCING BIOFUELS AND COPRODUCTS FROM LIGNOCELLULOSIC FEEDSTOCKS
Location: Bioenergy Research Unit
Title: Genetically engineered Escherichia coli FBR5: Part I. Comparison of high cell density bioreactors for enhanced ethanol production from xylose
Submitted to: Biotechnology Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2012
Publication Date: October 11, 2012
Citation: Qureshi, N., Dien, B.S., Liu, S., Saha, B.C., Hector, R.E., Cotta, M.A., Hughes, S.R. 2012. Genetically engineered Escherichia coli FBR5: Part I. Comparison of high cell density bioreactors for enhanced ethanol production from xylose. Biotechnology Progress. 28(5):1167-1178.
Interpretive Summary: In 2011, nearly 14 billion gallons of fuel ethanol was produced from primarily from corn. As a result of competition for corn for use in feed, food, and fuel, corn prices have increased significantly. Current gasoline prices have approached $4 per gallon and may continue to rise. The focus of this research is to produce ethanol at much lower prices than gasoline. Producing fuels such as ethanol from agricultural residues such as corn stover, which is available much economically ($50-60 per ton as opposed to corn at $263 per ton). However, traditional fermentation methods using these biomass feedstocks results in lower ethanol production rate or productivity. To improve productivity we developed novel fermentation systems where productivity was increased by 66 fold. Such increases would greatly improve the economics of ethanol production from agricultural residues. This research is expected to benefit US farmers, the biofuel industry, and the US public.
Five reactor systems (free cell batch, free cell continuous, entrapped cell immobilized, adsorbed cell packed bed, and cell recycle membrane reactors) were compared for ethanol production from xylose employing Escherichia coli FBR5. In the free cell batch and free cell continuous reactors (continuous stirred tank reactor – CSTR) productivities of 0.84 gL-1h-1 and 1.77 gL-1h-1 were achieved, respectively. A cell recycle membrane reactor resulted in the highest productivity of 55.56 gL-1h-1 which is an increase of 66 fold (e.g. 6614%) over the batch reactor. Calcium alginate gel CSTR resulted in a productivity of 2.04 gL-1h-1 while adsorbed cell packed bed reactor resulted in a productivity of 4.39 gL-1h-1. In the five reactor systems ethanol concentrations ranged from 18.9 to 40.30 gL-1 with metabolic yields from 0.44 to 0.51.