Cloning and characterization of enoate reductase with high β-ionone to dihydro-β-ionone bioconversion productivity

Abstract

Background: Dihydro-β-ionone is a principal aroma compound and has received considerable attention by flavor and fragrance industry. The traditional method of preparing dihydro-β-ionone has many drawbacks, which has restricted its industrial application. Therefore, it is necessary to find a biotechnological method to produce dihydro-β-ionone. Results: In this study, the enoate reductase with high conversion efficiency of β-ionone to dihydro-β-ionone, DBR1, was obtained by screening four genetically engineered bacteria. The product, dihydro-β-ionone, was analyzed by GC and GC-MS. The highest dihydro-β-ionone production with 308.3mg/L was detected in the recombinant strain expressing DBR1 which was later on expressed and purified. Its optimal temperature and pH were 45°C and 6.5, respectively. The greatest activity of the purified enzyme was 356.39U/mg using β-ionone as substrate. In the enzymatic conversion system, 1mM of β-ionone was transformed into 91.08mg/L of dihydro-β-ionone with 93.80% of molar conversion. Conclusion: DBR1 had high selectivity to hydrogenated the 10,11-unsaturated double bond of β-ionone as well as high catalytic efficiency for the conversion of β-ionone to dihydro-β-ionone. It is the first report on the bioconversion of β-ionone to dihydro-β-ionone by using enoate reductase.