Chemical additives in hydrothermal treatments: effects on saccharification and on the properties of hydrolysis lignin from pine, birch and willow wood

The use of chemical additives (1- and 2-naphthol, formaldehyde) in hydrothermal treatments of pine, birch, and willow wood was here evaluated as a means to improve the subsequent saccharification by enzymatic hydrolysis. In pine wood, the addition of 2-naphthol increased enzymatic saccharification from 20% up to 50% compared to water-only experiments. In birch and willow, almost complete (>90%) saccharification could be achieved even without additives. In willow, saccharification was partly hindered by the presence of bark, but the addition of 2-naphthol or formaldehyde slightly increased the sugar yields.
The effects of chemical additives on the properties of the lignin residues left after enzymatic hydrolysis of birch wood were also investigated. The use of 1- and 2-naphthol resulted in hydrolysis lignins with lower molar mass than in the case of water-only experiments. The use of 2-naphthol also induced changes to the chemical structure of lignin, which may provide advantages for its subsequent utilization in material applications.