Boosting enzymatic hydrolysis of steam-pretreated softwood by laccase and endo-β-mannanase enzymes from Streptomyces ipomoeae CECT 3341

Ligninases and hemicellulases are crucial as accessory enzymes to increase the enzymatic hydrolysis of lignocellulose, boosting sugars production from which biofuels and bioproducts could be obtained. In order to find new sources of these accessory enzymes, this study evaluates the potential of laccase and mannanase enzymes from Streptomyces ipomoeae for improving the conventional hydrolysis with commercial cellulases of steam-pretreated softwood. For that, different laccase treatment and mannanase supplementation strategies were performed. S. ipomoeae laccase increased both glucose and xylose production (17.8% and 9.3%, respectively), which was attributed to a removal of phenols of 29%. Moreover, the combination of laccase and alkaline extraction produced a lignin reduction of 16.2%, improving the glucose and xylose production by almost 41.3% and 44.9%, respectively. On the other hand, the supplementation of S. ipomoeae mannanase to the hydrolysis 24 h before the addition of cellulases increased the glucose (18.4%), xylose (12.3%), and mannose (47.2%) production.