Submitted to: Biotechnology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/4/1996
Publication Date: N/A
Interpretive Summary: Agricultural materials, particularly corn fiber, are available in sufficient quantities from the corn wet milling industry to serve as a low cost feedstock for production of fuel alcohol. Chemical, physical, and biological treatments are commonly used in the bioconversion of agricultural biomass to fermentable sugars. In this study, we used the ammonia fiber explosion (AFEX) process, coupled with enzyme treatment, for producing fermentable sugars from corn fiber. Three genetically engineered bacterial strains were then evaluated for their ability to ferment these sugars. Two strains were able to ferment the corn fiber sugars rapidly and in good yield. Commercial application of these strains will allow for increased fuel alcohol production from corn coproducts at a lower cost.
Technical Abstract: Fermentation of an enzymatic hydrolyzate of AFEX-pretreated corn fiber (containing a mixture of different sugars including glucose, xylose, arabinose, and galactose) by genetically-engineered Escherichia coli strain SL40 and KO11 and Klebsiella oxytoca strain P2 was investigated under pH-controlled conditions. Both E. coli strains (SL40 and KO11) efficiently utilized most of the sugars contained in the hydrolyzate and produced a maximum of 26.6 and 27.1 g/l ethanol, respectively, equivalent to 90 and 92% of the theoretical yield. Very little difference was observed in cell growth and ethanol production between fermentations of the enzymatic hydrolyzate and mixtures of pure sugars, simulating the hydrolyzate. These results confirm the fermentability of the AFEX-treated corn fiber hydrolyzate by ethanologenic E. coli. K. oxytoca strain P2, on the other hand, showed comparatively poor growth and ethanol production (maximum 20.0 g/l) from both enzymatic hydrolyzate and simulated sugar mixtures under the same fermentation conditions.