Effect of Acid Sulphite Pretreatment on Enzymatic Hydrolysis of Eucalypt, Broom, and Pine

Abstract

Wood chips of Eucalyptus globulus and Pinus pinaster and Cytisus striatus branches were subjected to acid sulphite pretreatment with different charges of sodium bisulphite (5–15%) and sulphuric acid (0–5%). Sugars, organic acids, and furans released in the pretreatment and enzymatic hydrolysates were analyzed by HPLC. The carbohydrates released in the pretreatment stage ranged between 2.5% and 18.7% (on wood weight) and are strongly species-dependent. The furans and formic acid represented less than 0.06% and 0.9% on wood weight, respectively, even under harsh reaction conditions. The enzymatic hydrolysis of the solid residues resulted in polysaccharide conversions in the range of 13% to 90%, depending on the pretreatment conditions and wood species. Eucalypt performs much better than the other species in both acid sulphite and enzymatic hydrolysis. The drying process before the enzymatic treatment has a markedly negative effect on the rate and extent of sugar release.

KEYWORDS:

• Acid sulphite pretreatment
• sugars released
• enzymatic hydrolysis
• Eucalyptus globulus
• Pinus pinaster
• Cytisus striatus