## 6 Types and Mechanisms of Removing Xenobiotics from Water
### Types of Lacase- Assisted Removing Xenobiotics from Water
#### 6.1.3 Pharmaceutical
In addition, the substrate specificity of the enzymes allows undesirable side reactions to be minimized by modifying the enzymes through genetic engineering and protein engineering methods [14; 225]. Enzymes are an encouraging technique for the selective removal of resistant compounds, such as pharmaceuticals from water and wastewater [40]. Research conducted in recent years has evaluated the effectiveness of PhAC removal by various forms of enzymes, such as whole cell cultures, crude extracts, free and immobilized enzymes, and enzymes obtained by heterologous expression or site-directed mutagenesis [14]. Purified extracellular lactose with a mass of 90 kDa secreted by _Sphingobacterium_ ksn-11, isolated from the soil of agricultural fields, was used by [PERSON] et al. (2020) after immobilization for the transformation of diclofenac [149]. The enzyme after purification was immobilized in sodium alginate-silicon dioxide-polyvinyl alcohol beads and assessed for diclofenac transformation efficiency. After 4 h incubation at 40 \({}^{\circ}\)C and pH 4.5, 75% of diclofenac was transformed without a mediator, and in the presence of ABTS, 81% of diclofenac was transformed within 90 min. LC-MS analysis confirmed that the immobilized increase converted the diclofenac to 4,5-dihydroxy diclofenac and 3-hydroxy diclofenac. The presence of the mediator had no effect on the quantity and quality of the products. The authors speculate that the removal of diclofenac occurs in the following steps: (i) hydroxylation, (ii) ring opening reaction and (iii) mineralization. The work clearly indicates the possibility of using _Sphingobacterium_ ksn-11 lacase immobilized on a polyvinyl-alginate-silicon dioxide matrix for further research on the degradation of endocrine disruptors and other xenobiotic compounds. It was recently discovered that the enzyme increase from the white rot fungus _T. hirsuta_ is capable of degrading chloramphenicol (2,2-dichloro-N-[(1R,2R)-1,3-dihydroxy-1-(4-nitrophenyl)]propane-2-yl]acetamide) in 7 days without mediators. Chloramphenicol is a broad-spectrum antibiotic pharmaceutical used to treat bacterial infections in humans and animals. It is one of the most durable thermotolerant xenobiotics among hospital waste. The use of the mediator-laccase system allowed for the effective removal of chloramphenicol in higher concentrations (10 mg/L) and shortened the time needed to completely remove the antibiotic from the reaction environment to 48 h. Laccase caused dehalogenation and oxidation of chloramphenicol to chloramphenicol alcoholichyde, which in MIC tests was nontoxic to the tested microorganisms (_Staphylococcus aureus_, _Escherichia coli_ and _Candida albicans_) [226]. _Streptomyces mutabilis_ A17 lacase obtained by solid-state fermentation on agro-waste degraded sulfonamide antibiotics. The maximum enzymatic activity was reached at 50 \({}^{\circ}\)C, pH 6.0 and 1 mM HBT for 1 h incubation. The degradation efficiency of sulfadiazine (SDZ) and sulfathiazole (STZ) sulfa antibiotics was approximately above 70 and 90%, respectively. The toxicity of the lacase-treated sulfonamide antibiotics tested in the microbial toxicity test against _B. cereus_ LC314797, _S. aureus_ KT337489, _S. enterica_ MK127926 and _K. pneumoniae_ KF771031 was significantly reduced. _S. mutabilis_ A17 lacase can be used in the enzymatic degradation and detoxification of sulfonamides from environmental pollutants [227]. Taken together, the results suggest an effective use of lacase and its mediators in the bioremediation of antibiotics and NSAIDs, such as diclofenac, one of the most persistent micropollutants in pharmaceutical waste.