Enhanced Tetracycline Degradation by Laccase Immobilized on Carboxymethyl Starch Magnetic Nanoparticles: Optimization of Degradation Conditions, Reusability, and Degradation Pathways.

Bioremediation using laccase (Lac) to degrade tetracycline (TC) contaminant is promising due to high specificity and selectivity of the biocatalyst. However, degradation parameters should be carefully studied to achieve maximum degradation efficiency. Thus, the current study aimed to degrade TC by employing Lac immobilized on novel carboxymethyl starch magnetic nanoparticles (CMS-MNP). The maximum TC degradation was determined via one-factor-at-a-time (OFAT) and central composite design (CCD). Using OFAT, the maximum TC degradation (56.3%) was achieved at initial TC concentration of 20 mg/mL, pH 6, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) concentration of 1.2 mM, and 10 h of reaction time. When CCD was employed, the TC degradation increased by one-fold with the highest TC degradation (62.1%) recorded at initial TC concentration of 25 mg/L, pH 5.7, ABTS concentration of 1.0 mM, and 11.8 h of reaction time. The CMS-MNP-Lac was reused for 7 cycles with a total TC degradation of 73 mg/L. The TC degradation in this study demonstrated outstanding potential and provided a green alternative for the treatment of TC contaminants in the environment.