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Nonionic surfactant Tween 80 is effective in alleviating the adsorption of lignocellulose-degrading enzymes onto lignin. However, the impacts of lignin structural characteristics on this mitigation effect of Tween 80 were still not clear. Herein, effects of Tween 80 on cellulase and xylanase adsorption on different enzymatic residual lignins (ERLs) and poplar samples were investigated. Besides, effects of Tween 80 on desorption of the two enzyme preparations from different ERLs and poplar samples were also evaluated. By adding Tween 80, the inhibition of ERLs to cellulase hydrolysis was offset and the positive role of Tween 80 in Avicel hydrolysis with presence of ERLs was more effective. Binding strength of cellulase with ERLs was alleviated from 236.0 − 410.9 to 43.9 − 116.6 mL/g after adding 0.5 mg/mL Tween 80. When ERLs was more hydrophobic and had more condensed phenolic OH, the alleviation effect of Tween 80 on cellulase adsorption on ERLs was intensified but its positive effect on enhancing cellulase desorption was weakened. Tween 80 was effective in increasing xylanase activity and preventing xylanase deactivation. With the increase of lignin content and phenolic OH in pretreated poplar, the effect of Tween 80 in alleviating xylanase adsorption on poplar samples was intensified but the effect in enhancing xylanase desorption from poplar samples was weakened. The results provided distinct findings to understand the interaction between Tween 80 and cellulase/xylanase in enzymatic saccharification of lignocelluloses. • Tween 80 alleviated cellulase adsorption on ERLs with more phenolic OH. • Tween 80 improved cellulase desorption from ERLs with less phenolic OH. • Tween 80 reduced xylanase adsorption on poplar with more lignin phenolic OH. • Tween 80 enhanced xylanase desorption from poplar with less lignin phenolic OH. [ABSTRACT FROM AUTHOR]

• Pretreatment of ERL at higher alkali strength relieved the cellulase adsorption. • Alkali pretreatment increased the desorption capacity of cellulase from ERLs. • Recoveries of cellulase from ERLs increased with the alkali strength increasing. • Bound-cellulase on alkali-pretreated ERLs showed activity, and can be reused easily. The knowledge about adsorption/desorption of cellulase on/from residual lignin is essential for efficient cellulose hydrolysis by recycling the cellulase from residual solid fraction. Herein, the impact of alkali pretreatment at different alkali strength on the adsorption/desorption of enzymatic residual lignins (ERLs) with cellulase was investigated. ERLs pretreated at stronger alkali strength had higher molecular weights and negative zeta potentials, but lower hydrophobicity. The inhibition of ERL to the enzymatic cellulose digestion was mitigated by alkali pretreatment, and inhibition degrees decreased from 21.5 % (with un-pretreated ERL) to 18.9 %, 12.9 %, and 10.8 % with the addition of ERLs treated with 0.5 %, 1.0 %, and 1.5 % (w/w) sodium hydroxide aqueous solution, respectively. The affinity of ERLs with cellulase diminished after alkali pretreatment, and the binding strength decreased from 183.0 to 130.7 mL/g with the alkali strength increasing, retaining more cellulase activities in supernatant. Desorption capacity of bound-cellulase from ERL increased after alkali pretreatment, and the recovery increased from 65.3% to 73.1% with the alkali strength increasing. The cellulase released after desorption exhibited hydrolytic activity, and higher glucose yields were obtained by the bound-cellulase on alkali-pretreated ERLs compared with that of un-pretreated ERL. The results provide references for the development of alkali pretreatment and recycling cellulase from residual lignin for efficient lignocellulosics digestion. [ABSTRACT FROM AUTHOR]

• Adsorption/desorption of cellulase on enzymatic residual lignin (ERL) was studied. • Dilute acid (DA) pretreatment of ERL at higher severity intensified the adsorption. • Desorption capacity of cellulase from ERL was decreased by DA pretreatment. • Recoveries of cellulase from ERLs decreased with the increase of severity factors. • Bound-cellulase on DA pretreated ERLs exhibited activity, but was hard to be reused. 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. [ABSTRACT FROM AUTHOR]

• Acid pretreatment increased surface lignin content on lignin-rich residues. • Alkali pretreatment resulted in less inhibitory lignin-rich residues. • The adsorption of cellulases on lignin-rich residues fitted Langmuir isotherm. • Cellulases adsorbed on lignin-rich residues could desorb and exhibited hydrolytic capacity. The impact of lignin-rich residues (LRRs) on cellulose hydrolysis and the adsorption/desorption of cellulases on/from LRRs were investigated. The LRRs were prepared from dilute acid (LRR-DA) and dilute alkaline (LRR-NaOH) -pretreated corn stover. The results showed that LRR-DA exhibited a stronger inhibitory effect than LRR-NaOH, which could be because of the higher surface lignin content in LRR-DA. The adsorption of cellulases on LRRs was in good agreement with the Langmuir isotherm model and LRR-DA exhibited the highest maximum adsorption capacity (48.4 mg/g). Cellulases that were adsorbed on LRR-DA and LRR-NaOH could be released by adding fresh buffer while retaining their hydrolytic capacities. This work shows that dilute alkaline pretreatment was more suitable than dilute acid pretreatment for corn stover because the residue from enzymatic hydrolysis of the dilute alkaline pretreatment exhibited a lower inhibitory effect and cellulases adsorption capacity. [ABSTRACT FROM AUTHOR]