The main goal of this work is to make soluble the hemicellulosic fraction of olive stone, an element that can later be fermented to produce ethanol using unconventional microorganisms capable of assimilating pentoses.
The olive stones were subjected to two different hemicellulose solubilization procedures. Each procedure consisted of two stages using a 2% w/v sulfuric acid solution at 130 °C for 1 h contact time. In the first solubilization process, olive stones and acid solution were mixed at 1:1 (w/w) ratio in each stage. In the second extraction step, the solid recovered from the first stage was used and fresh acid solution was added. In the second solubilization procedure, olive stones and acid solution were used at 1:2 w/w ratio in each stage. The resulting liquid from the first step was used as extracting solvent for the second step with a fresh olive stone lot.
Results show that both solubilization procedures are useful for obtaining a highly concentrated hemicellulosic sugar solution (above 130 g/L). Concerning extracted solids, a composition lower than 10% hemicellulose was obtained after the two steps of the first procedure (1:1 S/L ratio) and after the first step of the procedure using 1:2 S/L ratio.