Methoxychlor bioremediation by defined consortium of environmental Streptomyces strains

Abstract

Methoxychlor is an organochlorine pesticide used worldwide against several insect pests, resulting in human exposure. This pesticide mimics endocrine hormone functions, interfering with normal endocrine activity in humans and wildlife. For this reason, it is imperative to develop methods to remove this pesticide from the environment, and though, bioremediation using microorganisms results as an excellent strategy. Five Streptomyces spp. strains previously isolated from organochlorine-polluted sites and capable to grow and remove methoxychlor were combined as different mixed cultures to increase methoxychlor removal. From the 39 consortia tested, one consortium (Streptomyces spp. A6, A12, A14, M7) was selected because of its high pesticide removal and specific dechlorinase activity to be assayed on slurry and soil systems. This consortium showed higher biomass values (8.3 9 10 6 ± 5.7 9 10 5 CFU mL -1 ) and methoxychlor removal (56.2 ± 2.3 %) on enriched slurry than in nonenriched slurry (7.3 9 10 5 ± 1.2 9 10 5 CFU mL -1 and 45.6 ± 7.4 % of pesticide removal). In soil systems, Streptomyces consortium showed higher growth (1.0 9 10 11 ± 5.0 9 10 10 CFU g -1 ) than in enriched slurry, although differences in methoxychlor removal between both culture conditions were not statistically significant. Therefore, the selected Streptomyces consortium may be suitable for the development of in situ (soil) and ex situ (slurry bioreactor) bioremediation methods because of their potential to remove methoxychlor from different systems.

Enhanced Removal of a Pesticides Mixture by Single Cultures and Consortia of Free and ImmobilizedStreptomycesStrains

“…Based on obtained results (Section 3.1) and previous studies, which describe the actinobacteria abilities to use compounds with chlorine atoms in their molecules as carbon source [6, 27, 28, 43, 45], the growth of the strains as pure and mixed cultures in liquid MM supplemented with the pesticides mix (CP + PCP) was evaluated. Microbial biomass (dry weight) of the pure cultures ranged between 5 and 21.7 mg L −1 , whereas the growth of the mixed cultures was significantly higher ( P < 0.05), reaching a biomass of 98.3 mg L −1 for the mixed culture of Streptomyces spp.…”

Selection of an actinobacteria mixed culture for chlordane remediation. Pesticide effects on microbial morphology and bioemulsifier production

“…The six studied strains ( Streptomyces sp. A2, A5, A6, A13, M7, and S. coelicolor A3 (2)) were tested for antagonism by considering all possible combinations .…”

“…A 15 mL sample of the supernatant was taken from each culture in order to determine the residual CLD concentration by Gas Chromatography (GC, see below). The biomass was washed twice, suspended in 5 mL of sterile distilled water, and then lysed in a French press in order to obtain cell‐free extracts (CFEs) for specific dechlorinase activity (SDA) determinations .…”

“…In fact, microbial mixed cultures have been shown to be more suitable for bioremediation of recalcitrant compounds than pure cultures, since their biodiversity can enhance environmental survival and increase the number of catabolic pathways available for contaminant biodegradation . Previous research has shown that removal of others OCPs such as lindane and methoxychlor was improved when defined actinobacteria consortia were inoculated in liquid medium supplemented with these compounds, compared to the results from the corresponding individual strains . On the other hand, a variety of environmental microorganisms isolated from the region of Tucumán, Argentina, including native actinobacteria, are able to produce amphipathic compounds such as bioemulsifiers that exhibit activities at interfaces .…”

Understanding the simultaneous biodegradation of thiocyanate and salicylic acid by Paracoccus thiocyanatus and Pseudomonas putida

“…It is very common that the target contaminant can only be degraded by a very specific mixture of microorganisms that cooperate in a synergistic way. Therefore, a simplified model of the activated sludge can be built for the treatment of specific pollutant, including only the strains involved in their degradation (Chaudhari and Kodam 2010;Fuentes et al 2014;Huang et al 2013;Ibáñez et al 2014;McGenity et al 2012;Mikesková et al 2012). The aim is to obtain a system sufficiently complex to simulate a real sludge but, at the same time, simple enough to allow the study of the interactions between species (Mikesková et al 2012).…”