Efficiency of enzymatic and non-enzymatic catalysts in the synthesis of insoluble polyphenol and conductive polyaniline in water

Abstract

The present work analyzes the potential use of white-rot fungi (WRF) and hematin for phenol and aniline polymerization, as a low-cost alternative to horseradish peroxidase (HRPC). The objective is to evaluate the capability of these catalysts to produce tailor-made aniline as well as to eliminate phenols by precipitation from aqueous solution. 4-Aminoantypirine (4AAP) was used to test phenoxide formation by crude protein preparations of white-rot fungi at selected conditions. The crude extracts of Pleurotus sajor-caju (PSC) were selected because of the promising values obtained for the phenoxide formation rate. HRPC/H2O2 and P. sajor-caju derived enzymes/H2O2 (PSC/H2O2) systems produced soluble polyaniline in the presence of polystyrene sulphonated (PES), with high aniline conversions at 45 °C. For the case of insoluble polyphenol production, the PSC-derived enzymes, in absence of hydrogen peroxide, produced insoluble polyphenol with similar efficiencies as those found with HRPC or hematin in a one step phenol treatment (near 40% phenol conversion). For the aniline process, at least 75% aniline conversion was obtained when using PSC enzymes at room temperature. After long reaction times, the lignin-modifying enzymes derived from PSC only produced a conductive form of polyaniline (PANI) at lower temperatures than those required when employing HRPC. Fungal enzymes look promising for eliminating aniline/phenol from wastewaters since the obtained results demonstrated that they are able to polymerizate and precipitate them from aqueous solutions.