Kinetic understanding of fiber surface lignin effects on cellulase adsorption and hydrolysis

Cellulase hydrolysis is strongly affected by adsorption, which is inhibited by the non-productive binding between cellulase and lignin. However, lignin-bonded cellulase has also been found to be active in hydrolysis. Thus, in this work, lignin effects on cellulase adsorption and hydrolysis were studied using fibers with various surface lignin contents and structures based on kinetics. The surface lignin was changed by mechanical refining. Cellulase adsorbed on lignin showed reactivity to hydrolyze cellulose nearby according to the kinetic results, which is, however, much weaker compared with that by cellulose-bonded cellulase. With the decrease of surface lignin, this reactivity is also decreasing. Both cellulase adsorption and hydrolysis were increasing at first and then decreasing with the decrease of surface lignin as well as the lignin re-adsorption. It was concluded that lignin plays an important role in cellulase adsorption and non-productive binding occurs more easily between cellulase and the re-adsorbed lignin, as well as the residual lignin. At a relatively high surface lignin level, lignin structural and distribution changes were found to have a better effect on cellulase hydrolysis compared with lignin removal.