Abstract

BOTERO, L. R.; NAGLES, N.; QUINTERO, J.C.  and  PENUELA, G. A.. Effect of Methyl Parathion Concentration and Yeast Extract as Factors for Selecting Pesticide Degrading Microorganisms from Polluted Soils. Rev. ing. univ. Medellín [online]. 2011, vol.10, n.19, pp.13-20. ISSN 1692-3324.

Isolation and culture of microorganisms with capacity to degrade environmental pollutants are important for implementing bioremediation plans. This study is an evaluation of the yeast extract effect on both the microbial capacity to assimilate the organo-phosphorous pesticide methyl parathion and the isolation processes of microorganisms useful for degrading this pesticide. Microorganisms evaluated were obtained from fresh soil historically fumigate with this pesticide. Trials were conducted with defined solid means enriched with methyl parathion (0-60 mg L^-1) and yeast extract (0-0.5 g L^-1). It was found that microorganisms were able to assimilate up to 5 mg L^-1 methyl parathion with no yeast extract, without evidence of toxic effects. Assimilation capacity increased 10 mg L^-1 in cultures enriched with 0.5 mg L^-1 yeast extract. Yeast extract in doses used did not affect the isolation of microorganisms. However, isolation through direct culture in means enriched with methyl parathion as the only source of carbon was difficult due to the addition of organic matter of soil, which allowed the growth of resistant strains with no pesticide degrading capacity.

Keywords : isolation; yeast extract; methyl parathion; organo-phosphorous pesticide.

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