Conversion of corn cob hemicellulose hydrolysate into ethanol by recombinant Escherichia coli strain KO11.

KATIA GIANNI DE CARVALHO LIMA; CAROLINE MAKI TAKAHASHI; FLAVIO ALTERTHUM

Orlando, Florida

Congreso; American Society for Microbiology-101 General Meeting; 2001

Mild treatment of corn cob hemicellulose with dilute sulfuric acid at 121°C released 65.0-95.0 g/L of reducing sugars. The hydrolysate was neutralized by overliming with calcium oxide and adding 1 g/l of sodium sulfite. Recombinant Escherichia coli KO11 was an efficient byocatalyst for converting the resulting mixtures of pentoses and hexoses into ethanol. A two-stage fermentation was carried out, using E. coli in the first stepand baker s yeast in the second. After 110 h, E. coli produced 35.0-40.0 g/l of ethanol. The second stage was performed by addition of baker s yeast and sucrose (150.0 g/l) to the hydrolysate wine when ethanol fermentation by E. coli was completed. After 6 h of fermentation, the ethanol concentration accumulated in the medium was 110.0 g/l. This two-stage fermentation can turn the bioconversion of lignocellulose to ethanol more attractive, because the increase in alcoholic concentration turning the distillation process economically advantageous.