Enhancement of lipase activity in non-aqueous media upon immobilization on multi-walled carbon nanotubes

Abstract

BackgroundImmobilization of biologically active proteins on nanosized surfaces is a key process in bionanofabrication. Carbon nanotubes with their high surface areas, as well as useful electronic, thermal and mechanical properties, constitute important building blocks in the fabrication of novel functional materials.ResultsLipases from Candida rugosa (CRL) were found to be adsorbed on the multiwalled carbon nanotubes with very high retention of their biological activity (97%). The immobilized biocatalyst showed 2.2- and 14-fold increases in the initial rates of transesterification activity in nearly anhydrous hexane and water immiscible ionic liquid [Bmim] [PF6] respectively, as compared to the lyophilized powdered enzyme. It is presumed that the interaction with the hydrophobic surface of the nanotubes resulted in conformational changes leading to the 'open lid' structure of CRL. The immobilized enzyme was found to give 64% conversion over 24 h (as opposed to 14% with free enzyme) in the formation of butylbutyrate in nearly anhydrous hexane. Similarly, with ionic liquid [Bmim] [PF6], the immobilized enzyme allowed 71% conversion as compared to 16% with the free enzyme. The immobilized lipase also showed high enantioselectivity as determined by kinetic resolution of (±) 1-phenylethanol in [Bmim] [PF6]. While free CRL gave only 5% conversion after 36 h, the immobilized enzyme resulted in 37% conversion with > 99% enantiomeric excess. TEM studies on the immobilized biocatalyst showed that the enzyme is attached to the multiwalled nanotubes.ConclusionSuccessful immobilization of enzymes on nanosized carriers could pave the way for reduced reactor volumes required for biotransformations, as well as having a use in the construction of miniaturized biosensensor devices.

Use of high activity enzyme preparations in neat organic solvents for organic synthesis

“…While this work had nothing to do with enzyme catalysis in low water media, it is worth mentioning as this is of fundamental importance and such data is not always available with various systems. Immobilization of Candida rugosa lipase (CRL) on multi walled carbon nanotubes (MWNTs) by adsorption led to 2.2 and 14 fold increase in transesterification activity in n-hexane and [Bmim] [PF 6 ] respectively [85]. The immobilized lipase also showed high enantioselectivity in kinetic resolution of (±)-1-phenylethanol in [Bmim] [PF 6 ].…”

Nano-Immobilized Biocatalysts for Biodiesel Production from Renewable and Sustainable Resources

“…Carbon nanotubes based on graphitic sheets have a unique structure that rolls into a cylindrical shape [71]. Carbon nanotubes, including single-walled nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), are used for enzyme immobilization (Table 1) [43,[55][56][57][58][59]. Lee et al [55] immobilized PCL onto SWNTs using two different solvent systems (buffer and ionic liquid).…”

“…The immobilized lipase with 2.7% MWNT retained 96% of the initial activity after five reuses, whereas the immobilized lipase without MWNT was completely deactivated under the same condition. C. rugosa lipase (CRL) was also attached to MWNTs [43,[56][57][58][59]. CRL was immobilized on MWCT through physical adsorption, and a high retention of catalytic activity of up to 97% was observed.…”

“…CRL was immobilized on MWCT through physical adsorption, and a high retention of catalytic activity of up to 97% was observed. The immobilized CRL showed 2.2-and 14-fold increases in the initial rate of transesterification in hexane and water-immiscible ionic liquids (Bmim) (PF6), respectively [57]. Mohamad et al [58] reported a simple adsorption method to immobilize CRL onto acid-functionalized MWNTs (F-MWNTs).…”

Immobilization of Enterobacter aerogenes E13 strain culture medium, distinguished by its lipase activity, in the ethylcellulose microcapsules

“…The increase in the stability of lipases and other enzymes is usually reached by immobilizing them on various carriers. This way, an enzyme not only becomes more resistant to the environmental conditions, but it is also convenient to reuse [2][3][4][5]. Also, it is advantageous to use not only immobilized enzymes, but also immobilized enzymecell complexes.…”