Ethanol production from wheat straw by recombinant Escherichia coli strain FBR5 at high solid loading

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/L from non-abated WS hydrolyzate (total sugars, 86.6 ± 0.3 g/L) in 168 h at pH 7.0 and 35 °C. The bacterium produced 41.8 ± 0.0 g ethanol/L in 120 h from the bioabated WS by SHF. It produced 41.6 ± 0.7 g ethanol/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.