CHARCOAL ADSORPTION OF WOOD HYDROLYSATES FOR IMPROVING THEIR FERMENTABILITY - INFLUENCE OF THE OPERATIONAL CONDITIONS

Xylose solutions, obtained by acid hydrolysis of Eucalyptus wood were subjected to treatments with charcoal to remove lignin-derived compoun ds that can exert an inhibitory effect on subsequent fermentation stag es. The effects of three operational variables (hydrolysate concentrat ion, hydrolysate:charcoal ratio and adsorption time) on the concentrat ions of xylose, acetic acid and phenolics were considered. Additional experiments were performed with hydrolysates concentrated to a third o f the initial volume to evaluate the effects of temperature, pH and hy drolysate:charcoal ratio (using a broader range of ratios) on the adso rption process. Raw and charcoal-treated hydrolysates were used as fer mentation media for xylitol production by the yeast Debaryomyces hanse nii Treatments with a hydrolysate:charcoal ratio of 205 g/g were suffi cient for fermentation to occur; a higher charge of adsorbent did not result in significant improvements. Copyright (C) 1996 Elsevier Scienc e Ltd.