Identification and Characterization of a Novel Hyperthermostable Bifunctional Cellobiohydrolase- Xylanase Enzyme for Synergistic Effect With Commercial Cellulase on Pretreated Wheat Straw Degradation

Abstract

The novel cellobiohydrolase gene ctcel7 was identified from Chaetomium thermophilum, and its recombinant protein CtCel7, a member of glycoside hydrolase family 7, was heterologously expressed in Pichia pastoris and biochemically characterized. Compared with commercial hydrolases, purified CtCel7 exhibited superior bifunctional cellobiohydrolase and xylanase activities against microcrystalline cellulose and xylan, respectively, under optimal conditions of 60 • C and pH 4.0. Moreover, CtCel7 displayed remarkable thermostability with over 90% residual activity after heat (60 • C) treatment for 180 min. CtCel7 was insensitive to most detected cations and reagents and preferentially cleaved the β-1,4-glycosidic bond to generate oligosaccharides through the continuous saccharification of lignocellulosic substrates, which are crucial for various practical applications. Notably, the hydrolysis effect of a commercial cellulase cocktail on pretreated wheat straw was substantively improved by its combination with CtCel7. Taken together, these excellent properties distinguish CtCel7 as a robust candidate for the biotechnological production of biofuels and biobased chemicals.

Recombinant cellobiohydrolase of Myceliophthora thermophila: characterization and applicability in cellulose saccharification

“…Most of the GH6 cellulases are optimally active in the acidic range such as Ctcel6 of Chaetomium thermophilum and TlCel6A of Talaromyces leycettanus (Zhou et al 2017 ; Gu et al 2019 ) and also GH7 CBHs of M. thermophila (MtCel7A) and C. thermophilum (CtCel7) (Kadowaki et al 2018 ; Han et al 2020 ). Only one CBH (MoCel6A) of Magnaporthe oryzae has been reported with the pH optima of 9.0 (Takahashi et al 2010 ).…”

Activity and stability of hyperthermostable cellulases and xylanases in ionic liquids

“…They also resist denaturation by detergents and surfactants, often used to avoid irreversible adsorption of cellulase on the lignocellulosic substrates, and inactivation due to lignin (Rahikainen et al 2013;Shuddhodana et al 2018). Several reports have demonstrated the benefit of using hyperthermostable glycoside hydrolases in the hydrolysis of lignocelluloses compared to less thermostable enzymes (Peng et al 2015;H€ am€ al€ ainen et al 2016;Benedetti et al 2019;Han, Yang, et al 2020). In addition to hyperthermostable glycoside hydrolases found in thermophilic and hyperthermophilic microorganisms (Khare et al 2015;Shuddhodana et al 2018, Suleiman et al 2020) many such enzymes have also been found in metagenomic sources (Mientus et al 2013;Gladden et al 2014;Escuder-Rodr ıguez et al 2018).…”

Targeted genome editing of plants and plant cells for biomanufacturing

“…It is likely that successful biomass processing will require the activity of more than one enzyme, as discussed for the conversion of lignocellulosic biomass into sugars (Adsul et al 2020). Enzymes suitable for such reactions have already been found in plants (Huang et al 2019), mesophilic microorganisms (Jacomini et al 2020), and thermophiles (Han et al 2020), and have been identified via the metagenomic analysis of relevant microbial consortia, such as those found in biogas facilities (Klippel et al 2019).…”