Efficient degradation and detoxification of the emerging pollutants antibiotics including sulfonamides and cefixime by the LAC-48-2 laccase/mediator system.

This study systematically investigated the degradation and abolishment of antibiotic potency and phytotoxicity of 6 sulfonamide antibiotics (sulfadiazine, sulfapyridine, sulfamethoxazole, sulfathiazole, sulfameter, and sulfadimethoxine) and a cephalosporin, cefixime, using purified LAC-48-2 laccase. The LAC-48-2 laccase/tannic acid system showed strong degradation capacity for 6 individual sulfonamides and 2 sulfonamide mixtures. The degradation mechanism and pathways of the LAC-48-2 laccase/tannic acid system for different sulfonamides was further revealed. The LAC-48-2 laccase/tannic acid system also strongly alleviated or abolished the antibiotic potency (bacteriostatic activity toward 3 bacterial strains: Bacillus subtilis, Staphylococcus aureus, and Escherichia coli) of the 6 individual sulfonamides and sulfonamide mixtures. The LAC-48-2 laccase/tannic acid system demonstrated excellent detoxification effects on the phytotoxicity caused by 6 individual sulfonamides and various combinations of sulfonamide mixtures. The LAC-48-2 laccase/ABTS (2,2'-Azino-bis-(3-ethylbenzodihydrothiazoline-6-sulfonic acid) diammonium salt) system can quickly degrade the cephalosporin cefixime, with a degradation efficiency of 99.58% within 5 min. The LAC-48-2 laccase/ABTS system also effectively abolished the antibiotic potency and bacteriostatic activity of cefixime: the high bacteriostatic activity of cefixime decreased greatly or was completely abolished after laccase treatment. The LAC-48-2 laccase/ABTS system also efficiently degraded the sulfonamide + cefixime mixture, as laccase treatment could significantly decrease or even completely abolish the antibiotic potency (bacteriostatic activity) of the sulfonamide + cefixime mixture. Treatment with laccase demonstrated strong detoxification capabilities against the phytotoxicity of this mixed antibiotics.