Bioremediation of pesticides and metals: a discussion about different strategies using actinobacteria

ALVAREZ A; SAEZ MJ; DAVILA COSTA JS; POLTI MA; BENIMELI CS

Bioremediation of Agricultural soils

CRC Press. Taylor & Francis Group

Lugar: Boca Raton, FL; Año: 2019; p. 130 - 148

Highly toxic compounds have been released into the environment for direct or indirect application over a long period of time. Ecofriendly techniques have emerged for cleaning up polluted sites using plants and/or microbial species. This approach, known as bioremediation, is considered to be less invasive compared to conventional physicochemical techniques (Kidd et al. 2009). Bioremediation becomes important analyzing the high release of chemicals into the environment. Pesticides are probably the most widely distributed contaminants in the world. The disposal of obsolete pesticide stocks has resulted in many long-term contaminated sites many of which are illegal. For instance, the most important known illegal disposal of organochlorine pesticides (OC) (lindane, chlordane, methoxychlor, among others) and heavy metals [Cr(VI), Cu(II), Cd(II), among others], has been found in the northwest of Argentina (Chaile et al. 1999, Fuentes et al. 2010). Otherwise, pollution arising from agricultural activities is distributed over large areas and at low concentrations. In this context, residues of pesticides have been reported in samples of air (Lammel et al. 2007), water (Kumari et al. 2007), soil (Fuentes et al. 2010), fishes (Malik et al. 2007), and even in human beings (Ridolfi et al. 2014).Heavy metal contamination is also one of the most important environmental problems today. Polluted areas can be decontaminated using several methods; however, in case of heavy metal contamination, only a few techniques can be used because of the immutable and generally immobile nature of metals (Dávila Costa et al. 2011a, b). The wide use of heavy metals in several human activities such as industrial, agriculture, municipal landfill, and sewage disposal, significantly contribute to metal contamination (Fernández et al. 2014).Mixed pollution caused by the presence of organic and inorganic compounds tends to be concentrated in industrial zones (Mansour 2012). Thus, heavy metals and OC were found in water and silt samples from a major river basin from Northen Argentina (?The Salí basin?), at concentrations up to 10 times higher than allowed by law (Polti et al. 2007). Environments co-contaminated with metals and organic compounds are considered difficult to remediate because of the mixed nature of these pollutants. Moreover, more than one third of contaminated sites have more than one type of contaminant (Mansour 2012). Actinobacteria are a group of bacteria that play an important role in recycling substances in natural world, since they are able to metabolize complex organic matter (Kieser et al. 2000).The important ecological role performed by actinobacteria is demonstrated by their capability to remove pesticides and heavy metals, among others substances (Alvarez et al. 2017, Benimeli et al. 2003, 2006, 2007, Polti et al. 2009, 2011a, b, 2014). The physiological diversity of actinobacteria allows the production of a large number of metabolites with biotechnological importance included antibiotics, which are synthesized and excreted into a medium (Whitman et al. 2012). This book chaper focuses on how different techniques using actinobacteria can contribute to improve the bioremediation of pesticides and/or heavy metals.