ARS | Publication request: Ethanol production from wheat straw by recombinant Escherichia coli strain FBR5 at high solid loading

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 10, 2011
Publication Date: September 18, 2011
Citation: Saha, B.C., Nichols, N.N., Cotta, M.A. 2011. Ethanol production from wheat straw by recombinant Escherichia coli strain FBR5 at high solid loading. Bioresource Technology. 102(23):10892-10897.

Interpretive Summary: Wheat straw contains about 65% carbohydrates that can be used for production of fuel ethanol. Generally, four steps are involved for its conversion to ethanol: pretreatment, enzymatic hydrolysis, fermentation, and ethanol recovery. Increasing the ethanol titer in the fermentation broth is crucially important for cost reduction of cellulosic ethanol production due to high energy demand for ethanol recovered by distillation. In this research, we demonstrate that we can produce ethanol from wheat straw at a concentration which is considered by experts as economically viable for distillation.

Technical Abstract: Ethanol production by a recombinant bacterium from wheat straw (WS) at high solid loading by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) was studied. The yield of total sugars from dilute acid pretreated WS (150 g/L) after enzymatic saccharification was 86.3±1.5 g/L. The pretreated WS was bio-abated by growing a fungal strain aerobically in the liquid portion for 16 h. The recombinant Escherichia coli strain FBR5 produced 41.1±1.1 g ethanol per L from non-abated WS hydrolyzate (total sugars, 80.8±0.3 g/L) in 168 h at pH 7.0 and 35 deg C. The bacterium produced 41.8±0.0 g ethanol per L in 120 h from the bioabated WS by SHF. It produced 41.6±0.7 g ethanol per L in 120 h from bioabated WS by fed-batch SSF. This is the first report of the production of above 4% ethanol from a lignocellulosic hydrolyzate by the recombinant bacterium.