Growth ability and denitrification activity of bacterial isolates on media containing propoxur

Denitrifying bacteria are expected to be a promising organism to degrade pesticides by using them as carbon and nitrogen substrate. The potential of denitrifying bacterial isolates namely TK Bali, KT, UHT, L7T4, and C.pkr in degrading propoxur was studied through growth ability test and denitrification activity on three types of media containing propoxur. The media were NB (Nutrient Broth), MS (Mineral Salt), and MS + glucose added with various concentrations of propoxur (500, 1000, 1500 ppm). Bacterial growth was analyzed by measuring turbidity (OD) at a wavelength of 436 nm. Denitrification activity was measured by nitrate reduction capacity. Concentration of propoxur and isopropoxyphenol were measured using HPLC. The results showed that the highest growth and denitrification activities were in NB media. Denitrifying bacteria can grow in NB media containing propoxur up to 1500 ppm concentration, but the growth and denitrification activities decreased with the increasing concentration of propoxur. The denitrifying bacteria isolates seemed not to be able to use propoxur as the sole source of carbon and nitrogen. Denitrifying bacteria were resistant to propoxur to a certain concentration, but were unable to degrade propoxur, or it could degrade propoxur, but only in very low capacity. Isolate Brevundimonas diminuta, L7T4 was able to degrade propoxur to isopropoxyphenol in relatively low rate of degradation, less than 20 % of propoxur was degraded in 2 days of incubation.