A novel acid‐tolerant β‐xylanase fromScytalidium candidum3C for the synthesis ofo‐nitrophenyl xylooligosaccharides

Abstract

Endo‐β‐xylanases are hemicellulases involved in the conversion of xylans in plant biomass. Here, we report a novel acidophilic β‐xylanase (ScXynA) with high transglycosylation abilities that was isolated from the filamentous fungus Scytalidium candidum 3C. ScXynA was identified as a glycoside hydrolase family 10 (GH10) dimeric protein, with a molecular weight of 38 ± 5 kDa per subunit. The enzyme catalyzed the hydrolysis of different xylans under acidic conditions and was stable in the pH range 2.6–4.5. The kinetic parameters of ScXynA were determined in hydrolysis reactions with p‐nitrophenyl‐β‐d‐cellobioside (pNP‐β‐Cel) and p‐nitrophenyl‐β‐d‐xylobioside (pNP‐β‐Xyl2), and kcat/Km was found to be 0.43 ± 0.02 (s·mM)−1 and 57 ± 3 (s·mM)−1, respectively. In the catalysis of the transglycosylation o‐nitrophenyl‐β‐d‐xylobioside (oNP‐β‐Xyl2) acted both as a donor and an acceptor, resulting in the efficient production of o‐nitrophenyl xylooligosaccharides, with a degree of polymerization of 3–10 and o‐nitrophenyl‐β‐d‐xylotetraose (oNP‐β‐Xyl4) as the major product (18.5% yield). The modeled ScXynA structure showed a favorable position for ligand entry and o‐nitrophenyl group accommodation in the relatively open −3 subsite, while the cleavage site was covered with an extended loop. These structural features provide favorable conditions for transglycosylation with oNP‐β‐Xyl2. The acidophilic properties and high transglycosylation activity make ScXynA a suitable choice for various biotechnological applications, including the synthesis of valuable xylooligosaccharides.

Clustered surface amino acid residues modulate the acid stability of GH10 xylanase in fungi

“…MEY-1 maintained > 90% of its activity at pH 1.5 for 1 h (Luo et al 2009 ). GH10 ScXynA from Scytalidium candidum 3C displayed impressive acid tolerance, with a pH optimum of 3.5 (Eneyskaya et al 2020 ). Nevertheless, acid stability research has primarily been concentrated on the GH11 family due to its strong specificity to xylan.…”

Biochemical characterization of a novel acidophilic β-xylanase from Trichoderma asperellum ND-1 and its synergistic hydrolysis of beechwood xylan

“…The GH10 β-xylanases secreted by fungi, such as Phialophora sp. G5 (Zhang et al, 2011), Scytalidium candidum 3C (Eneyskaya et al, 2020), and Aureobasidium pullulans var.…”

“…The GH10 β-xylanases secreted by fungi, such as Phialophora sp. G5 ( Zhang et al, 2011 ), Scytalidium candidum 3C ( Eneyskaya et al, 2020 ), and Aureobasidium pullulans var. Melanigenum ATCC 20524 ( Ohta et al, 2001 ), displayed the highest activity at pH 4.0, 3.5, and 2.0, respectively.…”