Fibras de carbono modificadas com a álcool desidrogenase para o estudo da bioeletroxidação do etanol utilizando espectrometria de massas diferencial eletroquímica (DEMS)

Abstract

Regarding the bioelectrocatalysis of the ethanol oxidation, the electrodic surface modification and the optimization of enzymatic immobilization are necessary. In this scenario, the flexible carbon fibers (FCF) are noteworthy, because besides their surface can be modified in an easy way due the presence of carbon sp 2 , they have high mechanical resistance and elasticity, combined with high electrical and thermal conductivity. In this doctoral thesis, it is presented how to obtain bioelectrodes of FFC modified with the enzyme alcohol dehydrogenase from Saccharomyces cerevisiae (ADH) NAD-dependent, as well as to improve the oxidation of the coenzyme NADH (nicotinamide adenine dinucleotide). The results show that when FCF is previously submitted to an oxidative treatment in acidic medium (KMnO4/H2SO4), stable, robust and high surface area bioelectrodes are obtained. In addition, it was observed that these electrodes have oxygencontaining functional groups that improve the bioelectrocatalysis of ethanol oxidation.There is proposed that the presence of quinone groups is responsible for facilitating the regeneration of the coenzyme, i. e., these groups act decisively in the oxidation of NADH.The high quality of the bioelectrodes allowed it to maintain the catalytic activity of the ADH for long term, property crucial for the study of the oxidation of ethanol coupled to mass spectrometry (DEMS). By using DEMS, there were possible to observe coenzyme regeneration and the generation of acetaldehyde as a bioelectrooxidation product of ethanol, both at steady state, which were simultaneously observed. In summary, the present study introduces an to an approach that combines not only the development of chemically treated carbon fibers for application in bioelectrocatalysis, but also an unprecedented focus on the coupling between mass spectrometry and bioelectrochemistry for the resolution of enzymatic mechanisms.