CONVERSION OF CORN MILLING FIBROUS COPRODUCTS INTO ETHANOL BY RECOMBINANT ESCHERICHIA-COLI STRAINS K011 AND SL40

Corn hulls and corn germ meal were both evaluated as feedstocks for pr oduction of ethanol for biofuel. Currently, these fibrous co-products are combined with corn steep liquor and the fermentation bottoms (if a vailable) and marketed as cattle feed. Samples were obtained from wet and dry corn mills. The corn hulls and germ meal were evaluated for st arch and hemicellulose compositions. Starch contents were 12 to 32% w/ w and hemicellulose (arabinoxylans) contents were 23 to 64% w/w. Corn fibrous samples were hydrolysed, using dilute sulphuric acid, into mix ed sugar streams containing arabinose, glucose and xylose. Total sugar concentrations in the hydrolysate varied from 8.4 to 10.8% w/v. The h ydrolysates were fermented to ethanol using recombinant E. coli strain s K011 and SL40. Ethanol yields were 0.38 to 0.41 g ethanol produced/g total sugars consumed and fermentations were completed in 60 h or les s. However, residual xylose was detected for each hydrolysate fermenta tion and was especially significant for fermentations using strain SL4 0. Strain K011 was a superior ethanologenic strain compared with strai n SL40 in terms of both ethanol yield and maximum productivity.