Immobilization of Burkholderia cepacia on Pristine or Functionalized Multi-Walled Carbon Nanotubes and Application on Enzymatic Resolution of (RS)-1-Phenylethanol

The immobilization of Burkholderia cepacia lipase (BCL) on pristine or functionalized multi-walled carbon nanotubes (MWCNTs) was studied in the resolution of (RS)-1-phenylethanol. For the functionalization, three treatments were used, these being in H₂SO₄/HNO₃ (acid, MWCNTs-A), KOH (basic, MWCNTs-B) or in H₂O₂ (oxidizing agent, MWCNTs-O). It was found that the pristine or functionalized BCL/MWCNTs resulted in a 3-fold improvement in the conversion and in a 5-fold improvement in ee_s (enantiomeric excess of the substrate), when compared with free BCL under the same reaction conditions. This pristine or functionalized BCL/MWCNTs system could be reused for up to 8 times without significant decrease in the catalytic efficiency. Under the optimum conditions (pH of immobilization 6.0, 45 ºC and 25 mg/5 mg pristine or functionalized BCL/MWCNTs), the best results were obtained using BCL immobilized on MWCNTs-A. The simple process of physical adsorption of BCL onto MWCNTs-A has improved the catalytic efficiency when compared with free BCL and an increase in the stability was confirmed by thermogravimetric analysis (TGA).

Keywords:
multi-walled carbon nanotubes; functionalization; Burkholderia cepacia lipase; immobilization; enzymatic resolution