Abstract
Enzymatic conversion of polysaccharides in the lignocellulosic biomass is currently the subject of intensive research and will be a key technology in future biorefineries. Using a bioinformatics approach, we previously identified a putative endo-β-1,4-glucanase (DtCel5A) from Dictyoglomus thermophilum, a chemoorganotrophic and thermophilic bacterium. Here, we structurally and functionally characterize DtCel5A and show that it is endowed with remarkable thermal and chemical stability. The structural features of DtCel5A and of its complex with cellobiose have been investigated by combining X-ray crystallography and other biophysical studies. Importantly, biochemical assays show that DtCel5A retains its activity on cellulose at high temperatures and at elevated salt concentrations. These features make DtCel5A an enzyme with interesting biotechnological applications for biomass degradation.
Highlights
Cellulases are highly attractive enzymes for various industrial applications, such as lignocellulosic biomass conversion [1,2]
This complex is composed of three major hydrolases: endoglucanases, which attack low-crystallinity regions in the cellulose fibers by endo-action, creating free chain-ends; exoglucanases or cellobiohydrolases, which hydrolyze the 1,4-glycocidyc linkages to form cellobiose; and β-glucosidase, which converts cello-oligosaccharides and disaccharide cellobiose into glucose residues [5]
The full-length coding sequence of a putative endoglucanase from D. thermophilum was purchased from GENEWIZ (Sigma-Aldrich, Gillingham, Dorset, UK)
Summary
Cellulases are highly attractive enzymes for various industrial applications, such as lignocellulosic biomass conversion [1,2]. An enzymatic complex of cellulases is required for the complete hydrolysis of cellulosic polymers into fermentable sugars units This complex is composed of three major hydrolases: endoglucanases, which attack low-crystallinity regions in the cellulose fibers by endo-action, creating free chain-ends; exoglucanases or cellobiohydrolases, which hydrolyze the 1,4-glycocidyc linkages to form cellobiose; and β-glucosidase, which converts cello-oligosaccharides and disaccharide cellobiose into glucose residues [5]. Fungi, such as Trichoderma reesei, are industrially employed as a source of extracellular cellulases [6]. Dictyoglomus thermophilum, a chemoorganotrophic and thermophilic bacterium that encodes different thermostable xylanases and amylases [11], can be considered a promising source of new enzymes for the production of tailored cellulolytic cocktails for industrial application [12]
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