Unraveling Structural and Biochemical Insights into a Novel Thermo-Alkaline Pectate Lyase from <i>Caldicellulosiruptor bescii</i> for Sustainable Fabric Bioscouring

Pectate lyase (PL) holds significant potential for applications in various industries. However, the existing PL was unable to adapt to thermo-alkaline industrial environments. In this work, a PL from <i>Caldicellulosiruptor bescii</i> DSM 6725 (hereafter, CbPelD) was studied to disclose its structural and biochemical properties. CbPelD consisted of a putative signal peptide sequence, a short linker region, and a catalytic domain (PelD-II), along with an exoacting β-fructofuranosidase domain (PelD-I). In molecular dynamics simulation, PelD-II demonstrated significantly higher activity and thermal stability compared to other truncated enzymes of CbPelD. The optimal pH and temperature for PelD-II were 10.0 and 60 °C, respectively, with the specific activity increasing by 164-223% in the presence of Ca²⁺ or Ni²⁺. The exotype PelD-II exhibited efficient degradation of polygalacturonic acid (PGA) into unsaturated galacturonic acid (uG1), digalacturonic acid (uG2), and trigalacturonic acid (uG3). In the bioscouring assay, PelD-II exhibited a significant increase in the wetted fabric area to 6.072 ± 0.684 cm², which was about 7.9 times higher than untreated fabric. Scanning electron microscopy further revealed that treatment with PelD-II resulted in a smoother fiber surface, providing direct visual confirmation of the enzyme's action. These results highlight the potential of PelD-II for applications in the textile industries.