Abstract
ABSTRACT Nanomaterial-based biocatalysts have emerged as current carriers suitable for enzyme immobilization. The nano-sized materials provide large surface area for enzyme attachment, thus increasing the probability for its efficient catalyst activity. By using magnetized nanomaterials, enhancement of the downstream processing is evident as it eases the immobilized enzyme separation from the reaction mixture further. Lipase / maghemite composites were prepared by initial maghemite surface modification to cater to the needs for biocatalyst attachment. Surface modification using chitosan and subsequent cross-linking with glutaraldehyde provide a suitable environment for the enzyme to be immobilized. Optimization of the conditions for lipase immobilization was carried out using a response surface methodology (RSM) experimental design to obtain the precise optimized conditions for the process. Selected process variables involved were chosen and optimized conditions for lipase immobilization were 9 hour incubation time, 55°C incubation temperature and 12 % (v/v) glutaraldehyde content. The optimized immobilized lipase activity was 1.8 U. Characterizations of the on synthesized materials were also performed. The size distribution of maghemite nanomaterials was mainly within the range of 2-3 nm. Thermal properties of the synthesized maghemite was investigated using DSC and TGA analyses and we found that maghemite changes to hematite at 456.3°C. Magnetic properties of both untreated and lipase immobilized maghemite were studied using VSM and both were superparamagnetic nanomaterials with saturation magnetizations of 34.3 and 80.3, respectively.
Highlights
A nano-scale size maghemite and its biocompatibility enhance its desirability to be used as an enzyme immobilization matrix
The surface of maghemite was modified by adding -NH functional groupa and applying glutaraldehyde as cross-linker to the magnetic nanomaterial to further enhance lipase attachment
FT-IR spectra were used to confirm the successful immobilization of lipase onto maghemite
Summary
A nano-scale size maghemite and its biocompatibility enhance its desirability to be used as an enzyme immobilization matrix. This allows green technology to be manipulated in a wide range of applications. The system, changes when lipase is used in organic solutions, where it can catalyze formation of ester bonds in the presence of a minimal amount of water for enzyme activation. By immobilizing it onto a suitable carrier, the function of lipase can be tailored for specific required reactions of interest with enhanced stability at high enzyme activity. Compared to the free enzyme, the immobilized lipase shows advantages over the former through higher catalytic stability, functionality over continuous operations and lower operating cost, especially in the downstream processing (Liu et al, 2012)
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