Biocatalisadores heterogêneos baseados em lacases imobilizadas em polímeros para degradação disruptores endócrinos alquilfenois

Abstract

Emerging pollutants are chemicals with high toxicity and low biodegradability which can bioaccumulate in several environments. They are of great interest in the medical and environmental sectors due to their potential effect in humans and animals. Among the strategies for degrading emerging pollutants, the laccases (multicopper oxidase enzymes) stand out as excellent natural catalysts due to their great ability to oxidize different types of substrates. These biocatalysts have advantages over other conventional, highly toxic chemical catalysts. While the use of laccases in its free form is feasible, their immobilized stage presents several advantages such as the possibility of their over several consecutive cycles. This study aims to 1) assess the immobilization of laccase enzyme produced by the fungal species Trametes versicolor in divinylbenzene hydrophobic polymeric supports and evaluate the chemical behavior of this immobilized biocatalyst in the degradation of the contaminating agent nonylphenol (an endocrine disruptor). The supports were obtained by preparing a styrene divinylbenzene copolymer (STY-DVB), obtained through polymerization reaction in aqueous suspension. Optical microscopy inspection of the particles revealed individual, opaque and porous polydisperse polymer beads, which are characteristic of aqueous suspension polymerization. The STY-DVB copolymer was subjected to nitration reaction, reduction of nitro groups, and diazotation reaction. These chemical modification reactions were confirmed by infrared spectrometry (FT-IR). The laccase immobilization in the copolymer was monitored spectrophotometrically by the oxidation of the acidic substrate 2,2-azinobis-3-ethylbenzothiazole-6-sulfonate (ABTS). The immobilization yield was 89.6%, whereas the activity recovered from the immobilized laccase was only 3.62%. The analysis of the nonylphenol degradation using a fluorimeter indicated higher degradation obtained with immobilized laccase (74%), when compared to its free form (42%) under pH 5 and 5ºC.