Biodegradação de hormônios por bactérias com potencial aplicação no tratamento de efluentes sanitários: revisão sistemática e estudo de caso

Abstract

Sewage discharge into water bodies represents a challenge for both public health and the environment. In addition to the classic environmental pollutants, a group of emerging pollutants have been detected in environmental waters and waters already treated for human consumption. These micropollutant compounds, such as the natural estrogens estrone (E1), 17β-estradiol (E2) and estriol (E3) and synthetic ones, such as 17α-ethinylestradiol (EE2), are detected thanks to the application of advanced analytical techniques. Even at low concentration, these estrogens can interfere and disrupt important endocrine system processes in human and animals. Once deregulated, the endocrine system has the potential to affect other systems, such as the nervous, reproductive, and immune systems. Given the seriousness of this problem, researchers around the world have sought to develop efficient and low-cost systems capable of reducing the concentration of these compounds in the treated effluent. The present work aimed to review in the literature studies on estrogen reduction by microorganisms in effluent treatment processes. The work was divided into two stages, presenting a systematic review of the scientific literature on the degradation of estrogens by microorganisms in effluent treatment systems, using the descriptor "hormone biodegradation bacteria" in the Scopus electronic database, considering the period between years 2000 and 2020; Carry out, through a case study, enrichment tests and isolation of bacterial strains from water samples contaminated with high concentrations of synthetic estrogen EE2. The initial search for articles resulted in 42 works, among which 22 met the review's inclusion criteria. It was found that China and the United States of America are the countries with the greatest representation in studies on the biodegradation of estrogens in effluent treatment systems. Among selected articles, 63% of natural estrogen degradation trials reported complete degradation and 37% reported by-products without estrogenicity. On the other hand, only 18% of studies on the biodegradation of synthetic estrogen EE2 reported an absence of estrogenicity in the treated effluent. In the enrichment and isolation trial, the case study, two types of morphologically distinct colonies capable of using estrogen EE2 as a carbon source were isolated. Thus, the good results reported on the efficiency of estrogen degradation, through biological treatment systems, can be important indicators of the existence of viable technological conditions for the inclusion, in Brazilian environmental legislation, of estrogenicity criteria in treated effluents.