Abstract
BackgroundConsiderable works have been reported concerning the obstruction of enzymatic hydrolysis efficiency by lignin. However, there is a lack of information about the influence of lignin on the adsorption of cellulases on cellulose, along with the hydrolytic activity of the cellulases adsorbed on lignin. In addition, limited discovery has been reported about the influence of additives on cellulase desorption from lignin and lignocellulosic materials. In this work, the effects of lignin on cellulase adsorption and hydrolysis of Avicel were investigated and the effects of Tween 80 on cellulases adsorption and desorption on/from lignin and corn stover were explored.ResultsThe results showed that the maximum adsorption capacity of Avicel reduced from 276.9 to 179.7 and 112.1 mg/g cellulose with the addition of 1 and 10 mg lignin per gram Avicel, which indicated that lignin adsorbed on Avicel reduced surface area of cellulose and lignin available for cellulases. Cellulases adsorbed on lignin could be released by reaching new adsorption equilibrium between lignin and supernatants. In addition, cellulases desorbed from lignin still possess hydrolytic capacity. Tween 80 could adsorb onto both lignin and corn stover, and reduce the cellulase adsorption on them. Furthermore, Tween 80 could enhance desorption of cellulases from both lignin and corn stover, which might be due to the competitive adsorption between cellulases and Tween 80 on them.ConclusionsThe presence of lignin decreased the maximum adsorption capacity of cellulases on cellulose and the cellulases adsorbed on lignin could be released to supernatant, exhibiting hydrolytic activity. Tween 80 could alleviate the adsorption of cellulases and enhanced desorption of cellulases on/from lignin and corn stover. The conclusions of this work help us further understanding the role of lignin in the reduction of adsorption of cellulases on substrates, and the function of additives in cellulases adsorption and desorption on/from lignin and substrates.
Highlights
Considerable works have been reported concerning the obstruction of enzymatic hydrolysis efficiency by lignin
It is known that the different components of Celluclast 1.5L and Novozyme 188 (CEL) exhibit different adsorption behaviors with lignin [6, 12, 13], and the presence of lignin change the ratio of enzyme activities in supernatant needed for synergism during cellulose hydrolysis
The results here indicated that the enzyme components were abundant for the hydrolysis and slightly influenced by lignin in the initial 30 min, which was in good agreement with the report that the enzyme adsorbed onto non-cellulosic component of a pretreated feedstock is not likely to have a major impact on cellulose hydrolysis [24]
Summary
Considerable works have been reported concerning the obstruction of enzymatic hydrolysis efficiency by lignin. There is a lack of information about the influence of lignin on the adsorption of cellulases on cellulose, along with the hydrolytic activity of the cellulases adsorbed on lignin. Limited discovery has been reported about the influence of additives on cellulase desorption from lignin and lignocellulosic materials. The effects of lignin on cellulase adsorption and hydrolysis of Avicel were investigated and the effects of Tween 80 on cellulases adsorption and desorption on/from lignin and corn stover were explored. In order to efficiently convert biomass into sugars, it should maximally remove lignin and minimally modify polysaccharide by pretreatment [2]. In the unspecific binding of cellulases to lignin, the binding efficiency markedly decreased by removing of carbohydrate-binding module (CBM) from cellulases or mutating aromatic and polar residues on the
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