Characterization of a Salt-Tolerant and Cold-Adapted Xylanase from Bacillus cellulosilyticus

Jianzhong Sun, Sailing Shi, Jian Wu, Rongrong Xie, Alei Geng, Dao Chen Zhu

Abstract


A xylanase (Xyn10A) gene from the saline-alkali-tolerant microorganism Bacillus cellulosilyticus DSM 2522 was cloned and expressed in Escherichia coli BL21 (DE3). The open reading frame was composed of 1008 base pairs, and it encoded 335 amino acid residues belonging to glycosyl hydrolase family 10. The optimal temperature and pH of the purified Xyn10A were 40 °C and 8.0, respectively. The Xyn10A was sensitive to heat and showed obvious cold-adapted activity, retaining 38.3%, 55.7%, and 82.9% of the optimal activity at 4, 20, and 30 °C, respectively. Xyn10A also showed a high level of NaCl tolerance. The highest activity was observed with 1.5 M NaCl. The specific enzyme activity of Xyn10A was as much as 163.8 U/mg. Kinetic assays showed that Km, Vmax, and Kcat were 2.56 mg/mL, 202.5 μM/min/mg, and 132.6 /s, respectively. Additionally, the main hydrolysis products using birchwood xylan as substrate were xylobiose, xylotriose, and xylotetraose, as determined by thin layer chromatography analysis. As a cold-adapted and salt-tolerant enzyme, Xyn10A is an ideal candidate for further research and biotechnological applications.

Keywords


Xylanases; Bacillus cellulosilyticus; Cold adapted; Salt tolerant

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