Immobilization of Trametes hirsuta laccase into poly(3,​4-​ethylenedioxythiophene) and polyaniline polymer-​matrices

The immobilization of Trametes hirsuta laccase (ThL) in the poly(3,​4-​ethylenedioxythiophene) (PEDOT) and polyaniline (PANI) matrixes was carried out to study the catalytic effect of ThL in different biocathode structures in a biofuel cell application.  By using 2,​2'-​azinobis (3-​ethylbenzothiazoline-​6-​sulfonate) (ABTS) as a mediator compd., the immobilized ThL in both polymer matrixes, exhibited catalytic activity for the redn. of oxygen into water.  The amt. of ThL was adjustable in the PEDOT matrix by controlling the working parameters, such as the charge d. used in the electropolymn. of EDOT monomer and the ThL concn. used in the electropolymn. electrolyte.  In the PEDOT biocathode structure, the use of porous material as the PEDOT supporting template was studied to improve the c.d. generated per unit area​/vol.  Reticulated vitreous carbon foam (RVC foam) was chosen as the PEDOT supporting template material and the biocathodes were manufd. by in situ entrapment of ThL into PEDOT films polymd. on the RVC foam.  These biocathodes possessed a high cathodic open circuit potential and produced a large c.d., reaching 1 mA​/cm3 at 0.45 V when 19.5 μg​/mL of ThL was used in the electrolyte.  The performance of these biocathodes was extremely sensitive to variations in pH and the optimal working pH was ∼4.2.  The biocathode reserved 80​%, 50​%, and 30​% of the catalytic activity after storage in a +4° buffer soln. for 1 day, 1 wk, and 1 mo, resp.  The PANI matrix was prepd. in a form of printable ink where ThL was in situ entrapped in the PANI matrix during the laccase activated polymn. of aniline using a chem. batch reactor method.  Different amts. of the ThL-​contg. printable PANI ink were then applied on carbon paper and the performance of the ink was subsequently electrochem. characterized.  In this way, not only two different polymer matrixes, but also two different matrix manufg. procedures could be compared.