Biodegradation of organochlorine pesticides by bacteria grown in microniches of the porous structure of green bean coffee

In this paper, the authors propose a model for DDT biodegradation by bacteria grown in microniches created in the porous structure of green bean coffee. Five bacteria isolated from coffee beans, identified as Pseudomonas aeruginosa, P. putida, Stenotrophomonas maltophilia, Flavimonas oryzihabitans, and Morganella morganii. P. aeruginosa and F. oryzihabitans, were selected for pesticide degradation. Bacteria were selected according to their ability to grow on mineral media amended with: (a) glucose (10 g l−1), (b) peptone (2 g l−1), and (c) ground coffee beans (2 g l−1). These three media were supplemented with 50 mg l−1 of 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT) and endosulfan. GC/MS analysis demonstrated that the greatest DDT removal was obtained in the medium supplemented with coffee beans, where 1,1-dichloro-2,2′-bis (4-chlorophenyl)ethylene (DDE), 1-chloro-2,2-bis (4-chlorophenyl) ethane (DDMU) and 2,2′-bis (p-chlorophenyl)ethanol (DDOH) were detected. DDMU is a product of the reductive dechlorination of DDE, which in this system could be carried out under the anaerobic conditions in microniches present in the porous structure of the coffee bean. This was supported by scanning electron microscopy. Green bean coffee could be used as a nutrient source and as a support for bacterial growth in pesticide degradation.