Min Zheng,Xiangzhou Li,Dulin Yin,Steven R. Kirk,Hui Li,Peng Zhou,Yanhong Yang
Carveol is a rare fine chemical with specific biological activities and functions in nature. The artificial synthesis of carveol from plentiful and cheap turpentine is expected to further improve development of pharmaceutical and industrial applications. A new green catalytic system for the preparation of high-value carveol from α-epoxypinane is presented. A novel ammonium salt solid acid (AC-COIMI-NH4PW) was obtained from phosphotungstic acid bonded with imidazole basic site on nitrogen-doped activated carbon which, after ammonia fumigation, presented an excellent catalytic performance for the selective rearrangement of α-epoxypinane to carveol in DMF as solvent under mild reaction conditions. At 90 °C for 2 h, the conversion of α-epoxypinane could reach 98.9% and the selectivity of carveol was 50.6%. The acidic catalytic sites exhibited superior durability and the catalytic performance can be restored by supplementing the lost catalyst. Based on the investigation of catalytic processes, a parallel catalytic mechanism for the main product was proposed from the rearrangement of α-epoxypinane on AC-COIMI-NH4PW.
Kang An,Guoguo Wang,Lulu Zhang,Xuefeng Zhang,Jinchu Yang,Yongming Xu,Zhenzhen Huang,Jun Xi,Jun Meng,Hua Li,Beibei Zhao,Nannan Wang
Natural carvone is widely utilized in the food industry, cosmetics, agrochemicals, and pharmaceuticals due to its unique sensory characteristics and numerous biological effects. The enzyme carveol dehydrogenase catalyzes the oxidation reaction transforming carveol into carvone. In the present study, genome-based analysis of Klebsiella sp. O852 enabled the identification of four potential alcohol dehydrogenase (ADH) genes involved in the bioconversion process from carveol to carvone. These candidate genes were then heterologously expressed in Escherichia coli BL21(DE3), followed by purification and biochemical characterization of the recombinant proteins. All KlebADHs (ADHs from Klebsiella sp. O852) except KlebADH4 demonstrated carveol dehydrogenase activity and effectively catalyzed the conversion of carveol into carvone. Enzymatic experiments revealed optimal temperatures of 30–40 °C and an optimal pH of 9.0 for KlebADH3, KlebADH5, and KlebADH6. These enzymes were active with both NADP + and NAD + . Some organic solvents and metal ions, particularly Cu 2+ and Mn 2+ , significantly inhibited enzyme activity. Additionally, kinetic experiments indicated that KlebADH3 possessed the highest catalytic efficiency. This study expands the enzyme resources available for synthesizing carvone-derived compounds and provides a theoretical foundation for regulating enzymatic catalytic properties and improving carvone production.
Zehao Li,Wanying Wang,Guoguo Wang,Yingjie Feng,Yan Chen,Zhijian Li,Lulu Zhang,Jinchu Yang
Carvone has been widely used in pharmaceutical, food, cosmetic, and chemical industries due to its pleasant odor with high economic value and pharmacological activities. Carveol dehydrogenase is an enzyme that catalyzes the oxidation of carveol into carvone in the presence of NAD(P) + . In this study, two dehydrogenase genes from Klebsiella sp. O852 ( KlebADH1 and KlebADH2 ) were cloned and expressed in Escherichia coli BL21(DE3), and the purified enzymes were characterized for their biocatalytic properties. KlebADH1 and KlebADH2 displayed optimal catalytic activity at 40 °C and 30 °C, respectively, at pH 9. In addition to carveol, KlebADH1 had the potential to catalyze the oxidation of perillyl alcohol, nerol and geraniol, while borneol and geraniol could serve as potential substrates for KlebADH2. The substrate kinetic parameters of enzymes were performed by changing the concentration of carveol, and the results indicated that KlebADH2 exhibited a high affinity for carveol. Additionally, KlebADH1 and KlebADH2 were confirmed to possess carveol dehydrogenase activity through a double-enzyme-coupled (DEC) biotransformation system. The investigation of the biocatalytic properties of KlebADH1 and KlebADH2 laid a solid foundation for further study of carvone sustainable synthesis.
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