Impact of bleaching on subcritical water- and Formosolv-pretreated tulip tree to enhance enzyme accessibility

• A novel method was developed for selectively fractionating of cellulose, hemicellulose and lignin from a tulip tree.
• The isolated cellulose (∼98% glucan) had 23-fold higher enzymatic accessibility than raw substrate at low enzyme loadings (5 FPU/g of cellulose).

A novel method was developed for fractionating cellulose microfibrils from forest residue (tulip tree sawdust) to enhance cellulose digestibility, particularly at minimum enzyme loadings. This method involved three main stages: selective hemicellulose solubilization by subcritical water (SCW) pretreatment, delignification of the SCW-pretreated solids using the Formosolv process, and deformylation/bleaching of the cellulose pulp with alkaline hydrogen peroxide solution. This process produced nearly 98% white cellulose microfibrils with 23-fold higher conversion to glucose as compared to the raw substrate after 72 h of enzymatic hydrolysis. This study showed that cellulose swelling had the greatest effect on the enzymatic hydrolysis efficiency of delignified pulp obtained by the Formosolv process.