Enzyme immobilization has been known to be one of the methods to improve the stability and reusability of enzyme. In this study, a strategy to optimize laccase immobilization on polyethylene terephthalate grafted with maleic anhydride electrospun nanofiber mat (PET-g-MAH ENM) was developed. The development involves the screening and optimization processes of the crucial factors that influence the immobilization yield such as enzyme concentration, pH values, covalent bonding (CV) time, CV temperature, crosslinking (CL) time, CL temperature and glutaraldehyde concentration using two-level factorial design and Box-Behnken design (BBD), respectively. It was found that laccase concentration, pH values and glutaraldehyde concentration play important role in enhancing the immobilization yield of laccase on PET-g-MAH ENM in the screening process. Subsequently, the optimization result showed at 0.28 mg/ml laccase concentration, pH 3 and 0.45% (v/v) glutaraldehyde concentrations gave the highest immobilization yield at 87.64% which was 81.2% increment from the immobilization yield before optimization. Under the optimum condition, the immobilized laccase was able to oxidize 2, 2-azino-bis 3-ethylbenzothiazoline-6- sulfonic acid (ABTS) in a broad range of pH (pH 3-6) and temperature (20- 70 °C). Meanwhile, the kinetic parameters for Km and Vmax were 1.331 mM and 0.041 mM/min, respectively. It was concluded that the optimization of immobilized laccase on PET-g-MAH ENM enhance the performance of this biocatalyst.
This study investigates the feasibility of spent tea waste extract (STWE) as a green modifying agent for the modification of chitosan adsorbent towards aspirin removal. Response surface methodology based on Box-Behnken design was employed to find the optimal synthesis parameters (chitosan dosage, spent tea waste concentration, and impregnation time) for aspirin removal. The results revealed that the optimum conditions for preparing chitotea with 84.65% aspirin removal were 2.89 g of chitosan, 18.95 mg/mL of STWE, and 20.72 h of impregnation time. The surface chemistry and characteristics of chitosan were successfully altered and improved by STWE, as evidenced by FESEM, EDX, BET, and FTIR analysis. The adsorption data were best fitted to pseudo 2nd order, followed by chemisorption mechanisms. The maximum adsorption capacity of chitotea was 157.24 mg/g, as fitted by Langmuir, which is impressive for a green adsorbent with a simple synthesis method. Thermodynamic studies demonstrated the endothermic nature of aspirin adsorption onto chitotea.