Kriteria pemilihan kontraktor untuk melaksanakan kontrak pengurusan fasiliti

Abstract

Enzymes as biocatalysts in industries are more advantageous compared to chemical catalysts because of their low operating conditions, less complexity, and environmentally-friendly property. Laccase, an oxidoreductase enzyme, is foreseen to be used in various industries as a biocatalyst. However, the use of free laccase in industries often suffers some limitations, such as high production cost, instability issues, low recovery, and reusability problems. These problems can be overcome by enzyme immobilization technology, which offers enhancements to free enzyme's stability. The advent of nanotechnology has introduced electrospun nanofiber mat as a carrier for enzyme immobilization. The mat is foreseen to be implemented in the enzymatic membrane bioreactors of continuous flow processes. In this study, polyethylene terephthalate (PET) was grafted with maleic anhydride (MAH) (PET-g-MAH) and spun through electrospinning into nanofiber mats with an average fiber diameter of 844 ± 149 nm before it was used as the carrier of immobilized laccase. Three different immobilization methods were used: physical adsorption on PET nanofiber mats, covalent bonding, and covalent bonding of cross-linked laccase aggregate with glutaraldehyde as the cross-linker. The combination of 0.28 mg/ml laccase concentration, pH 3 citrate buffer, 0.45 % (v/v) glutaraldehyde concentration, 1.5 hr of covalent bonding time at 22.7 oC, and 1 hr of cross-linking time at 20 oC contributed to the optimum immobilization yield (87.64 %). The adsorption of laccase on PET-g-MAH nanofiber mats obeyed the pseudo-first-order, and the biosorption isotherms correlated well with the Freundlich isotherm model. The optimized immobilized laccase was able to withstand high temperature (60 oC) and also oxidized 2, 2-azino-bis 3-ethylbenzothiazoline-6- sulfonic acid (ABTS) at a broad range of pH (pH 3 to pH 6) and temperature (20 oC to 70 oC). It also managed to retain 77.55 % of its initial activity after 10 repeated cycles of ABTS oxidation and 29.22 % after 30 days storage at 4 oC in pH 3 buffer. In conclusion, the results showed that the laccase immobilized on the PET-g-MAH nanofiber mat might have great potential to be used in industries.