Comparative studies of free and immobilized  onto functionalized multiwalled carbon nanotubes for soyasapogenol B production

Amin, Hala A.; Haroun, Ahmed A.

doi:10.4103/epj.epj_28_17

Comparative studies of free and immobilized onto functionalized multiwalled carbon nanotubes for soyasapogenol B production

Authors

Abstract

Objective
This research focuses on the microbial transformation of soybean saponins to soyasapogenol B (SB) by cells producing saponin hydrolase (CSH) as a whole-cell biocatalyst. Multiwalled carbon nanotubes (MWCNTs) have been reported to have several properties that render them ideal support systems with the advantage of being further functionalizable at their surface.
Materials and methods
CSH was covalently immobilized onto carboxy-functionalized MWCNTs by different methods including direct immobilization as well as immobilization by glutaraldehyde or carbodiimide chemistry.
Results and conclusion
Results showed that direct immobilization of CSH onto oxidized MWCNTs was the best method accompanied by about an 80% immobilization yield. The optimum temperature was around 50°C for both the free and the immobilized CSH (MWCNTs–CSH conjugate). The apparent activation energy () was increased from 1.05 to 2.84 kcal/mol by immobilization. The immobilized enzyme also showed significantly improved thermal stability. The calculated half-life values of MWCNTs–CSH conjugate at 70, 80, and 90°C (55, 33.3, and 29.7 h, respectively) were higher than those of free CSH (36.1, 28.0, and 23.2 h, respectively). The MWCNTs–CSH conjugate showed higher (0.45 μmol) compared with the free CSH (0.41 μmol), whereas for the MWCNTs–CSH conjugate was smaller than that for free CSH. The MWCNTs–CSH conjugate morphology was examined using transmission electron microscope.

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