Anais da 43ª Reunião Anual Virtual da SBQ

Laccase-based bioprocesses represent a fascinating perspective for the removal of emerging contaminants in waters and wastewaters. Biocatalytic treatment using oxidoreductase enzymes, especially laccases, has received the attention of the scientific community for biodegradation of pharmaceutical compounds, such as acetaminophen, to less harmful compounds. However, enzymes are required to be immobilized on supports to be reusable and maintain their activity. In this study, the laccase from Trametes versicolor was immobilized in avocado seed biochar to remove acetaminophen (ACT) from aqueous solution. Initially, the preparation of the avocado seed biochar (ASB) was carried by pyrolysis of avocado seed at 500ºC for 30 min. Afterward, two treatments were employed to activate the pyrolyzed material. In the first treatment, 2 g of ASB material was treated with 50 mL of 2 mol L⁻¹ citric acid by shaking at 80 rpm for 24 h. The activated biochar was labeled as A-ASB. In the second treatment, 50 mg of treated material with citric acid was placed in contact with 10 mL of glutaraldehyde 1% and 5% (v/v) for 3 h at 80 rpm. These samples were labeled as G1A-ASB and G5A-ASB, respectively. The immobilization procedure was performed by mixing 10 mg of samples ASB, A-ASB, G1A-ASB, or G5A-ASB with 7.5 U of laccase enzyme (U = enzyme unit) in pH 5.0 at 25°C under agitation at 50 rpm for 24h. After immobilization, enzymatic activity was determined by oxidation of 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to cationic radical ABTS⁺, which was quantified by UV-Vis spectroscopy (ʎ = 420 nm). The results shown in Figure 1 demonstrate that the material G1A-ASB presented higher immobilization efficiency (IE) and a higher activity of laccase (U) by gram of material (U/g). Therefore, G1A-ASB support with immobilized laccase was applied in the removal of ACT. For this, 10 mg of support with and without immobilized laccase was placed in contact with 5 mL of ACT (30 mg L^-1) for 24 h at 80 rpm. After, ACT concentration in the supernatant was measured by capillary electrophoresis. The results (Figure 2) show that the support without laccase (G1A-ASB) removed only 7% of ACT, while the support with immobilized laccase (LG1A-ASB) removed 73%. Thus, this study demonstrated that avocado seed biochar has potential to be used as support in laccase immobilization since the laccase remained active in support, degrading the ACT.