Abstract
Swollenins exist within some fungal species and are candidate accessory proteins for the biodegradation of cellulosic substrates. Here, we describe the identification of a swollenin gene, Tlswo, in Talaromyces leycettanus JCM12802. Tlswo was successfully expressed in both Trichoderma reesei and Pichia pastoris. Assay results indicate that TlSWO is capable of releasing reducing sugars from lichenan, barley β-glucan, carboxymethyl cellulose sodium (CMC-Na) and laminarin. The specific activity of TlSWO toward lichenan, barley β-glucan, carboxymethyl cellulose sodium (CMC-Na) and laminarin is 9.0 ± 0.100, 8.9 ± 0.100, 2.3 ± 0.002 and 0.79 ± 0.002 U/mg, respectively. Additionally, TlSWO had disruptive activity on Avicel and a synergistic effect with cellobiohydrolases, increasing the activity on pretreated corn stover by up to 72.2%. The functional diversity of TlSWO broadens its applicability in experimental settings, and indicating that it may be a promising candidate for future industrial applications.
Highlights
Lignocellulosic biomass or plant dry matter, has been considered an alternative to fossil fuels
Further analysis using PROSITE demonstrated that TlSWO consists of three domains, fungal-type carbohydratebinding module family 1 (CBM1), family 45 endoglucanase-like domain of expansin (Expansin_EG45) and a cellulose-binding-like domain of expansin (Expansin_CBD), all of which are typical of swollenins from fungi (Figure 1)
Similar to results observed for SWOI, the other two swollenins, Af SWO1 from A. fumigatus and SWO2 from T. pseudokoningii have shown hydrolytic activity on various substrates, suggesting that these proteins interact with cellulose or hemicellulose (Chen et al, 2010; Zhou et al, 2011)
Summary
Lignocellulosic biomass or plant dry matter, has been considered an alternative to fossil fuels. The enzymatic deconstruction of biomass that follows pretreatment can be enhanced using a number of non-glycoside hydrolase accessory proteins These enzymes include, but are not limited to, expansins, loosenins, cerato-platanin proteins and certain other types of carbohydrate binding modules (CBM) (Gourlay et al, 2013; Payne et al, 2015; Guo et al, 2017; Luti et al, 2020). Among these proteins, expansins have been widely found in plant cell walls where they function to loosen the cellular wall (Marowa et al, 2016)
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