FERMENTATION OF ORANGE-PEEL HYDROLYSATES BY ETHANOLOGENIC ESCHERICHIA-COLI - EFFECTS OF NUTRITIONAL SUPPLEMENTS

Orange peel, an abundant byproduct of the citrus processing industry, is converted to a mixture of glucose, galacturonic acid, fructose, ara binose, galactose, and xylose by hydrolysis with mixed pectinase and c ellulase enzymes. All these sugars can be fermented to ethanol or etha nol and acetic acid by the recombinant bacterium Escherichia coli KO11 . The fermentation efficiency is improved by the addition of yeast ext ract, tryptone, mixed amino acids, corn steep liquor, or by proteolyti c digestion of endogenous proteins. Batch fermentations of supplemente d peel hydrolysate containing 111 g/L of initial total sugars produced 35-38 g/L of ethanol in 48-72 h and a 75-85% yield.