Adsorption and desorption of cellulase on/from enzymatic residual lignin after alkali pretreatment

Abstract

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.