The study of the biphasic microbial oxidation of naphthalene to cis-naphthalene dihydrodiol using Escherichia coli carrying naphthalene dioxygenase enzyme

The application of green chemistry principles is important for the sustainable production of industrial chemicals. The objective of this research was to apply biological means to carry out the selective oxidations of aryl substrates to prepare key chiral intermediates. The selective oxidation of naphthalene to produce optically pure (+)-cis-1,2-naphthalene dihydrodiol (NDHD) has gained interest owing to its potential application as a chiral synthon for the manufacture of specialty chemicals. The productivity in making NDHD was increased using 20% dodecane organic phase and 40 g/l naphthalene to 1.75 g-diol/g-cdw/h for the first six hours in shake flasks. The biocatalyst remained active for at least 12 h of biotransformation and was shown to be stable for at least four cycles with the suspended and immobilized cells. Suspended resting cells retained activity for four runs for 6 h recycle, but the stability was not retained for more than two runs for 12 h recycle. After protocol modification, biocatalyst recycle up to 8 cycles was performed at 6 and 12 hours, and activity decreased over time. Shake flask experiments were scaled to 625 mL in a DASGIP reactor. Reaction rates increased from 0.4 to 2.0 g/L/h by increasing the cell mass in the reactor.;Recycle experiments with cells immobilized in calcium alginate determined that the stability of the 12 h recycle was improved by immobilization although the activity of immobilized cells was less than that of suspended cells. However, the activity of immobilized cells was improved by increasing the amount of calcium alginate beads per reaction.;Ionic liquids (ILs) are explored as an alternative to organic solvents providing a green solvent for catalysis. A growth study in the presence of an IL [HMIM][BTA] was done and it was found to inhibit the growth of E. coli. The activity of the cells in the presence of IL was low compared to results with dodecane as the second phase; cells were able to produce NDHD in small amounts. These results lay the groundwork for further application of green chemistry to optimize biocatalysis for the synthesis of chiral intermediates.