Adsorption and desorption of cellulase on/from lignin pretreated by dilute acid with different severities

Desorption of cellulase from lignin is necessary to recycle cellulase in enzymatic hydrolysis. Currently, the knowledge about cellulase desorption from lignin is still limited. In present work, the adsorption and desorption of cellulase on/from enzymatic residual lignins (ERLs) pretreated with dilute acid at different severities were investigated. The results showed that the molecular weights of dilute acid-pretreated ERLs (DA-ERLs) decreased with the increase of severity. The hydrophobicity and contents of condensed phenolic structures in ERLs increased after DA pretreatment with the increase of severity. Compared with un-pretreated ERL, DA-ERLs pretreated with severity factors of 1.17, 1.51, and 1.69 increased the inhibition degree of cellulose hydrolysis from 21.5 % (ERL) to 24.6 %, 28.5 % and 31.9 %, respectively. DA-ERLs pretreated at higher severities exhibited larger adsorption capacities with individual cellulase components. DA pretreatment of ERL at higher severities intensified the binding with cellulase. The binding strength between lignin and cellulase increased from 236.0 mL/g to 261.5-410.9 mL/g with the increase of severity. DA pretreatment decreased the desorption capacity of cellulase from ERLs. The recovery of cellulase from lignin decreased from 78.6% to 36.9%-14.7 % with the increase of severity. The cellulase desorbed from ERLs remained portion of activities, but the cellulase bound on DA-ERLs was hard to be released and provided a lower glucose yield (4.8 %-5.9 %) than that on un-pretreated ERL (16.2 %). The results reported here will aid cellulase recycling and efficient hydrolysis of lignocellulose after dilute acid pretreatment.