Aerobic biodegradation of the a, b and g-hexachlorocyclohexane isomers by actinobacteria

CUOZZO S.A; PONCE J; BENIMELI C.S.; AMOROSO M.J.

Puerto Vallarta

Simposio; 16th International Symposium on the Biology of Actinomycetes; 2011

Hexachlorocyclohexane (HCH) is a highly toxic and persistent organochloride pesticide that has caused serious environmental problems since it began to be produced at the beginning of the 1940s. During the synthesis process of HCH different isomers are produced. All HCH isomers have the same molecular formula 1,2,3,4,5,6-HCH, but are differentiated by variations in the axial-equatorial positions of the molecules of chlorine around a ring of 6 carbons. Of all the isomers, only -HCH (lindane), possesses insecticidal activity. Therefore the need arises by the environmental bioremediation with actinobacteria. For this reason we have focused on the selection of actinobacteria able to degrade HCH isomers. Five actinobacteria strains, previously isolated from a pesticides contaminated soil, and the reference strain Streptomyces coelicolor A3(2) were selected. All strains were grown in Minimal Medium (MM), supplemented with each of the different HCH isomers (,  y -HCH). All cultures were incubated on a rotatory shaker (100 rpm) at 30 ºC, for 96 h. Centrifuged culture supernatants (9000 g, 10 min, 4 ºC) were used to determine residual HCH isomers by Gas Chromatography with Electron Capture Detector (GC/ECD). The biomass production was estimated by washing the pellets with 25mMTris-EDTA buffer (pH 8.0) and drying to constant weight at 105 ºC. After 96 h of incubation, we observed that actinobacteria strains Streptomyces sp. A2, A5 and A8 were able to grow in the presence of -HCH as the only carbon source. When the MM was supplemented with -HCH, strains capable to grow in this condition were S. coelicolor A3(2), Streptomyces sp. A2, and A8 whereas in the presence of -HCH Streptomyces sp. A5 and A8 showed the maximum growth. Is the first time that the aerobic degradation of HCH-isomers by indigenous actinobacteria was studied, especially -HCH which is the most recalcitrant of the HCH isomers.