A new laccase-mediator system facing the biodegradation challenge: Insight into the NSAIDs removal

• Published in: Chemosphere (Oxford) 2019-01, Vol.215, p.535-542
• Main Authors: Apriceno, Azzurra, Astolfi, Maria Luisa, Girelli, Anna Maria, Scuto, Francesca Romana
• Format: Article
• Language: English
• Subjects: ABTS; Anti-Inflammatory Agents, Non-Steroidal - chemistry; Biodegradation, Environmental; Chitosan support; Diclofenac - chemistry; Hydroxylation; Immobilized laccase; Ketoprofen - chemistry; Laccase - chemistry; Naproxen - chemistry; NSAIDs degradation; Trametes - metabolism
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2018.10.086

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely found pollutants in the aquatic environment and the currently available treatments for their removal are usually associated with some drawbacks. The aim of this research was to apply a laccase-mediator system for the degradation of some commonly used NSAIDs, namely diclofenac (DCF), naproxen (NAP) and ketoprofen (KP). The biocatalyst was obtained by direct immobilization on chitosan beads of a periodate-oxided laccase from Trametes versicolor. A preliminary study aimed to optimize DCF degradation in the presence of 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonicacid) diammonium salt (ABTS) as mediator. It turned out that pH 3 and a 1:1 M ratio for ABTS:drug were the best experimental conditions under which DCF was degraded at 90% after 3 h. In addition, an efficient reuse of the biocatalyst for up to 5 cycles emerged. DCF was further mixed with naproxen and ketoprofen to test whether laccase was still able to eliminate DCF and eventually act on the other compounds. At just 0.02 U of laccase activity, diclofenac was completely degraded within 3 h, while an almost complete removal for naproxen (∼90%) and a partial removal for ketoprofen (30%) occurred in 7 d when drugs were added at high concentrations (78.5 μM, 98 μM and 108 μM, respectively). After 7 d of degradation, transformation products of diclofenac, identified as hydroxylated compounds, disappeared. Naproxen products were, instead, reduced to very small amounts. [Display omitted] •Laccase is immobilized via oxidized carbohydrate moiety on chitosan beads.•NSAIDs compounds in water can be efficiently eliminated by a batch laccase reactor.•Pharmaceuticals removal progresses until products mineralization.