Cellulases are known to be adsorbed by lignins, thus reducing their catalytic potential for cellulose digestion.139 140 Steam pretreatment may even increase the potential cellulase-binding properties of lignin.141 Enzymatic removal of lignin residues from pretreated lignocellulosic materials has received little attention. Laccase (p-diphenol:O2 oxidoreductase, EC 1.10.3.2) catalyzes the cleavage of C-C and C-ether bonds in lignins.142 Laccase treatment of steam-pretreated softwoods was shown to improve subsequent cellulase-mediated saccharification.143 The second major class of lignin-degrading enzymes, peroxidases, includes many additional targets for enzyme manufacturers to produce and test as adjuncts to cellulases for the digestion of pretreated lignocellulosic materials.144

Coating the surfaces of lignin residues in pretreated lignocellulosic materials by adding a protein before cellulase incubation is an extension of a long-practiced biochemist’s technique known as “sacrificial protein” use to protect sensitive enzymes. Adding a commercially available protein, bovine serum albumin, to corn stover pretreated with either dilute sulfuric acid or ammonia fiber explosion and to Douglas fir pretreated by SO2 steam explosion increases cellulose saccharification and is a promising strategy to reduce enzyme requirements for feedstock processing if a suitable source of low-cost protein is identified.145