DEGRADATION OF DDT AND DDE BY CHEESE MICROORGANISMS

Representative microorganisms of the diverse flora associated with several varieties of surface‐ripened cheese were isolated. Species of streptococci, micrococci, yeasts and Gram‐positive rods accounted for most of the isolates. These were incubated at 32°C in media containing 0.5 ppm lindane, p‐p DDE, and p‐p DDT. The pesticides were dissolved in a small amount of ethanol to facilitate incorporation into the media. Following incubation for 10 days, the concentrations of residual pesticides were determined by electron capture gas chromatography. The growth of streptococci and micrococci isolates did not apear to produce any changes in pesticide levels, though they apparently were uninhibited by the pesticides. However, the growth of other isolates dechlorinated p‐p DDT. Moreover, aerobic growth of geotrichum species caused almost complete disappearance of the p‐p DDT and p‐p DDE peaks from the gas chromatograms. These results suggest the possibility that residues of DDT and DDE might be degraded if they are present in certain types of surface‐ripened cheeses. Copyright © 1969, Wiley Blackwell. All rights reserved