Abstract: A novel lytic polysaccharide monooxygenase, TtLPMO9Y, was cloned and expressed from Thermothelomyces thermophilus. Its enzymatic properties were characterized, and its role in the degradation process of cellulose and pectin in plant cell walls was investigated. The results showed that the optimal reaction temperature and pH for TtLPMO9Y was 50 ℃ and 7, respectively. After treatment at 80 ℃ for 4 h, 63% of the enzyme activity remained, demonstrating good thermal stability. After treatment with TtLPMO9Y at 2, 4, 6, and 8 μmol/L combined with 1 mg/mL of pectinase, the clarity of fresh fruit juice increased by 4.9%–16.2% and the turbidity decreased 5.3%–21.0% when compared with pectinase alone. Furthermore, the combined use of 1, 3, and 5 μmol/L of TtLPMO9Y with cellulase increased the yield of reducing sugar from microcrystalline cellulose and corn straw by 21%–66% and 29%–91%, respectively, compared with cellulase alone. In conclusion, TtLPMO9Yhas good enzymatic properties and can effectively promote the degradation of cellulose and pectin in plant cell walls, demonstrating significant application value in juice processing.

Key words: lytic polysaccharide monooxygenase; enzymatic properties; juice clarification; cellulose degradation