Abstract:Objective This study aims to investigate the application of a novel thermophilic lytic polysaccharide monooxygenase (LPMO) in the efficient cellulase-mediated hydrolysis of lignocellulosic substrates.Method The thermophilic enzyme mgLPMO10, derived from a compost metagenome, was heterologously expressed in Escherichia coli (E. coli). Its expression level was improved by modifying the signal peptide of the expression vector and induction conditions (temperature, IPTG concentration, and induction time). The enzyme was then characterized in terms of the optimal temperature, optimal pH, thermal stability, pH stability, and the effects of metal ions on its enzyme activity. Subsequently, the synergistic hydrolysis efficiency of mgLPMO10 with two thermophilic endoglucanases (TnCelB and DtCelB) at different molar ratios toward phosphoric acid-swollen cellulose (PASC) and other cellulose substrates was evaluated at 70 ℃.Result The coding sequence of the pelB signal peptide in the expression vector significantly improved the expression level of mgLPMO10. After optimization (induction with 0.50 mmol/L IPTG at 28 ℃ for 18 h), the expression level reached 12.9 mg/L, representing a 90% increase compared with the pre-optimized level. The optimal reaction conditions of mgLPMO10 were 70 ℃ and pH 6.0, and this enzyme showed the maximum enzyme activity of 25.5 U/g. After adding 5 mmol/L Mn2+, its enzyme activity increased by 75%. When synergistically hydrolyzing PASC with TnCelB or DtCelB, the enzyme exhibits synergy degrees of 123% and 138%, respectively. Moreover, mgLPMO10 exhibited significant promoting effects on other cellulose substrates.Conclusion The combination of mgLPMO10 and thermophilic endoglucanases can significantly enhance cellulose hydrolysis efficiency under high-temperature conditions. The study provides an important enzyme and a theoretical basis for the development of high-temperature lignocellulose biorefining processes.
