Simultaneous degradation of mixed pesticides by pure and mixed actinobacteria cultures

FUENTES, MARÍA S.; BRICEÑO, GABRIELA E.; ALVAREZ, ANALÍA; DIEZ, MARÍA C.; AMOROSO, MARÍA J.

San Miguel de Tucumán

Congreso; VII Congreso Argentino de Microbiología General "SAMIGE DEL BICENTENARIO"; 2011

Several pesticides are commonly used to increase the agricultural productivity. The organochlorine pesticides have long persistence, tendency towards bioaccumulation and potential toxicity towards non-target organisms. This group of compounds has been replaced by the less persistent and more effective organophosphorus compounds. However, these pesticides possess high mammalian toxicity. The use of microorganisms to detoxify contaminants is an effective biotechnological approach to clean up polluted environments. Mixed cultures have been shown to be more suitable for bioremediation compared with pure cultures. In the natural environment, organic compounds degradation is often carried out by mixed microbial communities. The aim of this work was to demonstrate the efficiency of pure and mixed actinobacteria cultures isolated from Chilean (AC5, AC9) and Argentinean (Streptomyces sp. A2, A5, A11, M7) contaminated sites for removing a mixture of chlorpyrifos (CP) and pentachlorophenol (PCP) from liquid medium. Preliminary actinobacteria tolerance assays were carried out in Petri plates containing solid minimal medium (MM) in the presence of CP and PCP mix (1.66 mg L-1 respectively). In most of cases, actinobacteria strains showed high tolerance levels to the pesticides mix. To determine the potential antagonistic effect of the actinobacteria strains, Petri dishes with solid starch casein medium were sown confronting individual strains with each other actinobacteria. No growth inhibition was observed, so, there were no responses to antagonism between the assayed strains. The ability of pure and mixed actinobacteria cultures to growth and remove CP and PCP mix in liquid MM was evaluated determining growth (dry weight), pesticide removal (gas chromatography) and pH variation. After 72 h of incubation, the microbial growth was 5 to 21.7 (pure cultures), 98.3 (Chilean mixed culture) and 101.7 mg L-1 (Argentinean mixed culture). pH values were 7, except for Streptomyces sp. A5 and both mixed cultures, where values varying from 8.5 to 8.7. The CP removal ability by pure and both mixed cultures was higher than PCP removal. Streptomyces sp. M7 and the mixed culture AC5-AC9 showed the best CP removal percentages (99.2% and 91.5% respectively), while Streptomyces sp. A5 and the mixed culture Streptomyces sp. A2-A5-A11-M7 showed the maximal PCP removal ability (10.6% and 10.1% respectively). These microorganisms showed high degradation capacity to remove organophosphorus pesticides such as chlorpyrifos. Therefore actinobacterias isolated from contaminated sites could be recommended for bioremediation  of  different pesticides types.