Unraveling the effects of laccase treatment on enzymatic hydrolysis of steam-exploded wheat straw

• The activity of β-glucosidase was slightly reduced by laccases.
• Total phenolic content decreased 80% points after laccase treatment.
• Laccase treatment increased the Klason lignin in the lignocellulosic substrate.
• Laccases modified the infrared adsorption spectra of the lignocellulosic substrate.
• Grafting process is limiting the accessibility of cellulolytic enzymes to cellulose.

Laccase enzymes are promising detoxifying agents during lignocellulosic bioethanol production from wheat straw. However, they affect the enzymatic hydrolysis of this material by lowering the glucose recovery yields. This work aimed at explaining the negative effects of laccase on enzymatic hydrolysis.Relative glucose recovery in presence of laccase (10 IU/g substrate) with model cellulosic substrate (Sigmacell) at 10% (w/v) was almost 10% points lower (P < 0.01) than in the absence of laccase. This fact could be due to an increase in the competition of cellulose binding sites between the enzymes and a slight inhibition of β-glucosidase activity. However, enzymatic hydrolysis and infrared spectra of laccase-treated and untreated wheat straw filtered pretreated residue (WS-FPR), revealed that a grafting process of phenoxy radicals onto the lignin fiber could be the cause of diminished accessibility of cellulases to cellulose in pretreated wheat straw.