Non-productive adsorption of bacterial β-glucosidases on lignins is electrostatically modulated and depends on the presence of fibronection type III-like domain

Abstract

Non-productive adsorption of cellulases onto lignins is an important mechanism that negatively affects the enzymatic hydrolysis of lignocellulose biomass. Here, we examined the non-productive adsorption of two bacterial β-glucosidases (GH1 and GH3) on lignins. The results showed that β-glucosidases can adsorb to lignins through different mechanisms. GH1 β-glucosidase adsorption onto lignins was found to be strongly pH-dependent, suggesting that the adsorption is electrostatically modulated. For GH3 β-glucosidase, the results suggested that the fibronectin type III-like domain interacts with lignins through electrostatic and hydrophobic interactions that can partially, or completely, overcome repulsive electrostatic forces between the catalytic domain and lignins. Finally, the increase of temperature did not result in the increase of β-glucosidases adsorption, probably because there is no significant increase in hydrophobic regions in the β-glucosidases structures. The data provided here can be useful for biotechnological applications, especially in the field of plant structural polysaccharides conversion into bioenergy and bioproducts.

Systematic studies of the interactions between a model polyphenol compound and microbial β-glucosidases

“…As extensively reported in published studies, nonionic surfactants reduce or completely neutralize the inhibitory effect because the surfactant binds to TAN [18,19]. Thus, we measured the hydrolytic activities of microbial β-glucosidases in the presence of TAN in combination with Triton X-100 (Fig 2).…”

“…It is widely accepted that the presence of residual soluble phenols produced after pretreatment of lignocellulosic biomass can significantly reduce the enzymatic hydrolysis of cellulose to glucose [14–19]. Therefore, several studies have investigated the effect of polyphenolic compounds on enzymatic activity, and as a consequence, contributed to the improvement of cost-effective production of biofuels [14–19].…”

“…It is widely accepted that the presence of residual soluble phenols produced after pretreatment of lignocellulosic biomass can significantly reduce the enzymatic hydrolysis of cellulose to glucose [14–19]. Therefore, several studies have investigated the effect of polyphenolic compounds on enzymatic activity, and as a consequence, contributed to the improvement of cost-effective production of biofuels [14–19]. The archaeon Pyrococcus furiosus and the bacterium Thermotoga petrophila are hyperthermophilic microorganisms that produce various enzymes with potential industrial, including β-glucosidases [19,25,26,36,41,42].…”

“…Lignin composition may vary from plant to plant, and is composed mainly of phenylpropane units (guaiacyl propanol, syringyl propanol, and p -hydroxyphenyl propanol) [12,13]. The enzymatic hydrolysis of cellulose to glucose by cellulases may be inhibited in the presence of residual lignin produced as a result of pretreatment, the latter which frequently results in considerable amounts of insoluble lignin fragments and soluble phenolics [14–19]. The mechanism of enzyme inhibition may involve both non-productive adsorption of cellulases onto insoluble lignin fragments, as well as interactions with solubilized phenolics [14–19].…”

“…The enzymatic hydrolysis of cellulose to glucose by cellulases may be inhibited in the presence of residual lignin produced as a result of pretreatment, the latter which frequently results in considerable amounts of insoluble lignin fragments and soluble phenolics [14–19]. The mechanism of enzyme inhibition may involve both non-productive adsorption of cellulases onto insoluble lignin fragments, as well as interactions with solubilized phenolics [14–19]. Therefore, a better understanding of the interaction of cellulases with lignin and its soluble derivatives can help to improve the development of biofuel production technologies.…”