A bifunctional cellulase–xylanase of a new Chryseobacterium strain isolated from the dung of a straw‐fed cattle

Abstract

SummaryA new cellulolytic strain of Chryseobacterium genus was screened from the dung of a cattle fed with cereal straw. A putative cellulase gene (cbGH5) belonging to glycoside hydrolase family 5 subfamily 46 (GH5_46) was identified and cloned by degenerate PCR plus genome walking. The CbGH5 protein was overexpressed in Pichia pastoris, purified and characterized. It is the first bifunctional cellulase–xylanase reported in GH5_46 as well as in Chryseobacterium genus. The enzyme showed an endoglucanase activity on carboxymethylcellulose of 3237 μmol min−1 mg−1 at pH 9, 90 °C and a xylanase activity on birchwood xylan of 1793 μmol min−1 mg−1 at pH 8, 90 °C. The activity level and thermophilicity are in the front rank of all the known cellulases and xylanases. Core hydrophobicity had a positive effect on the thermophilicity of this enzyme. When similar quantity of enzymatic activity units was applied on the straws of wheat, rice, corn and oilseed rape, CbGH5 could obtain 3.5–5.0× glucose and 1.2–1.8× xylose than a mixed commercial cellulase plus xylanase of Novozymes. When applied on spent mushroom substrates made from the four straws, CbGH5 could obtain 9.2–15.7× glucose and 3.5–4.3× xylose than the mixed Novozymes cellulase+xylanase. The results suggest that CbGH5 could be a promising candidate for industrial lignocellulosic biomass conversion.

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

“…Notably, EDTA and SDS severely compromised the efficiency of the bifunctional activities of CtCel7. Similar results were detected for a GH7 endo-β-1,4-glucanase (Cel7A) (Liu et al, 2015), a GH10 xylanase (Xyln-SH1) (Cheng et al, 2012) and a GH5 bifunctional cellulasexylanase (CbGH5) (Tan et al, 2018). The beneficial effect of Tween-20, Triton X-100 and PEG-600 on enzyme activity may be attributed to the effect of surfactant binding on enzyme secondary and tertiary structure that results in a more flexible conformation (Delorme et al, 2011;Holmberg, 2018).…”

“…Consistently, the optimal conditions for CtCel7-xylanase activity were pH 4.0 and 60 • C (Figures 4A,B). The concordant optimal reaction conditions for the bifunctional cellobiohydrolase and xylanase activities of CtCel7 are presumably related to the single substrate-binding tunnel threaded through the CtCel7_CD region (Figures 2A,B; Tan et al, 2018).…”

“…Because multifunctional glycoside hydrolases with excellent activity are favorable for carbohydrate conversion (Cao et al, 2018;Wang et al, 2019), much effort has been devoted to the bioprospecting of these potent catalysts to allow their application in industrial fields. Although many multifunctional GHs have been identified (Yang et al, 2017;Tan et al, 2018;Liu et al, 2019), an inherent enzymatic feature of significant thermostability, which is preferred for practical production, has rarely been reported, especially for a thermostable bifunctional cellobiohydrolase capable of xylan hydrolysis.…”

Biochemical characterization of a key laccase-like multicopper oxidase of artificially cultivable Morchella importuna provides insights into plant-litter decomposition

“…After 30 h of fermentation, the culture supernatant was collected, concentrated by ultra-filtration, de-glycosylated and purified with an AKTA pure automatic chromatography system, using the procedures described previously (Tan et al 2018). The buffer was replaced with 20-mM PBS buffer (pH 5.0) using an ultra-filtration centrifugal tube with a 3-kDa molecular weight (Mw) cut-off (Merck-Millipore, Shanghai, China), and the total volume was then adjusted to 9.5 ml.…”

Enzymatic identification and functional sites study of a novel cold-active cellulase (MkCel5) from Microbacterium kitamiensea

“…Some of the cellulases previously reported and applied on the market were mesophilic and thermophilic enzymes [5][6][7][8][9][10][11][12], while a few cold-adapted cellulases have been studied, such as CaCel from Cryptopygus antarctica [13], CelG from Fibrobacter succinogenes S85 [14], CelM of Pseudomonas sp. MM15 [15], etc.…”