The fermentations experiments were carried out in
2.2.2. Sulfuric ENMD-2076 hydrolysis
To convert the polysaccharides into fermentable monomeric sugars, the pre-hydrolysate was completely hydrolyzed with 1.5% wt/wt sulfuric acid at 121 °C for 60 min. The hydrolysate was filtered and sterilized by passing through a 1.5 μm filter. Untreated and treated hydrolysates were neutralized with Ca(OH)2, from an initial pH of 1.34 to a final pH of 6.5.
2.2.3. Hydrolysate detoxification
The procedure developed by Ajao et al. (2015a) in a previous work on the production of ethanol from a similar hemicellulosic pre-hydrolysate extracted from wood chips was used for the hydrolysate detoxification in the current work.
Flocculation experiments were carried out in jar tests using ferric sulfate Fe2(SO4)3 as a flocculating agent. A volume of 1 L of wood hydrolysate was mixed with 200 g/L of ferric sulfate solution to reach a ratio [Fe]/[phenols] of 1 and the mixture was homogenized by agitation at 150 rpm. The pH was then adjusted to 6.8 with Ca(OH)2 and the agitation was resumed for 30 min at 50 rpm. At the end of the agitation period, the mixture was left to rest for 2 h so that a sedimentation occurs. The supernatant was then filtered with a 1.5 μm filter and used as a carbon source to carry out the fermentation studies.