초록
The hydrophobic bacterium Rhodococcus rhodochrous NBRC15564 was employed as a whole-cell biocatalyst to examine its potential for bioconversion in solvent-free organic media. The genes encoding two different thermostable alcohol dehydrogenases (ADH<SUB>Tt1</SUB> and ADH<SUB>Tt2</SUB>) of Thermus thermophilus HB27 were expressed in R. rhodochrous cells. To inactivate indigenous mesophilic enzymes in R. rhodochrous, transformant cells were heated at 70<SUP>o</SUP>C for 10min. Heat-treated hydrophobic wet cells were used for the bioconversion of 2,2,2-trifluoroacetophenone (TFAP) to α-(trifluoromethyl) benzyl alcohol (TFMBA) as a model reaction with ADH<SUB>Tt1</SUB>. NADH, which was supplied in aqueous solution, was regenerated by converting cyclohexanol to cyclohexanone by ADH<SUB>Tt2</SUB>. All reactions were performed by suspending heat-treated cells in solvent-free organic media consisting of 3.7M TFAP and 4.8M cyclohexanol (1:1, v/v ratio) at 60<SUP>o</SUP>C. When 800mg heat-treated R. rhodochrous cells were dispersed in 2mL of solvent-free organic media (400mgcells/mL), the product concentration reached about 3.6M TFMBA by 48h with a total NADH turnover number of approximately 900. The overall productivity was 190molTFMBA/kgcells/h.