Comparison of different procedures for the detoxification of eucalyptus hemicellulosic hydrolysate for use in fermentative processes

Eucalyptus (Eucalyptus grandis) shavings were submitted to an acid hydrolysis process with the aim of obtaining a hemicellulosic hydrolysate rich in fermentable sugars. However, the hydrolysate obtained contained, in addition to sugars, several compounds that are toxic to microorganisms, namely furfural, hydroxymethylfurfural, acetic acid and phenolics. In order to produce a hydrolysate suitable for use in fermentative processes, several procedures were evaluated for hydrolysate detoxification, including concentration by vacuum evaporation and adsorption on activated charcoal, diatomaceous earths, ion-exchange resin or adsorbent resin. Hydrolysate concentration was especially effective for furfural removal, whereas the adsorbent resin was efficient in removing hydroxymethylfurfural, phenolics and acetic acid. Combination of this resin with activated charcoal was better than with diatomaceous earths for removal of acetic acid and phenolics. The best detoxification procedure evaluated was based on hydrolysate concentration followed by adsorption on activated charcoal and adsorbent resin. By this treatment, removal rates of 82.5, 100, 100 and 94% were attained for acetic acid, furfural, hydroxymethylfurfural and phenolics, respectively.