Evaluation of various pesticides-degrading pure bacterial cultures isolated from pesticide-contaminated soils in Ecuador

Abstract

Due to the intensive use of pesticides within the greenhouse-rose production, remediation of polluted soils has become a hot topic for researchers in recent decades. Several bacterial strains having the ability to utilize various pesticides as a sole source of carbon and energy were isolated from pesticidecontaminated soils of Urcuquí, Ecuador. According to phenotypical, physiological, and biochemical characterizations, and 16S rRNA gene sequence analysis, the isolated pure bacterial cultures were identified as Pseudomonas putida sp. strain B1, Acinetobacter sp. strain B2 and Arthrobacter sp. strain B3. The bacterial isolates were used individually and mixed cultures were used in the laboratory and field experimentations for the degradation of various pesticides like Ridomil MZ 68 MG, Fitoraz WP 76, Cleaner, Decis 2.5 CE, Score 250 EC, Zero 5 EC, Bravo 720 SC, Meltatox, Mirage 45 CE and Teldor Combi at 50 mgL^-1. The bacterial growth was monitored on both liquid culture medium (in laboratory) and field experiments by spectrophotometer method, Neubauer camera and colony-forming units. In addition, the degradation of individual pesticides (50 mgL^-1) was determined by ultra-high performance liquid chromatography-tandem mass-spectrometry and UV-VIS spectrophotometer. The results showed that the highest growth rate of microbial consortium was observed during degradation of various pesticides than individual pure bacteria for both experiments. In addition, most pesticides were completely degraded by microbial consortium after 60 days.

Keywords: Bioremediation, spectrophotometer, bioreactors, pesticides, consortium