Biodegradation of Pendimethalin by Three strains of Bacteria Isolated from Pesticide-Polluted Soils

Abstract

Biodegradation of pendimethalin by three strains of bacteria
viz; Pseudomonas aeruginosa, Bacillus mycoides and Bacillus cereus
isolated from pesticides polluted soil was studied in mineral salt medium.
Pendimethalin was incubated with each of the three strains of bacteria and
samples were drawn at 0, 3, 7, 15 and 30 days for gas chromatographic
analysis. The loss in the initial concentration (400 ppm) over time was
monitored and used to compute the half lives following a biphasic model.
GC-MS was used to identify the major metabolites as well as to re-
confirm the identity of the starting material (pendimethalin). The results
showed that the remaining amounts of pendimethalin recovered from
media inoculated with Pseudomonas aeruginosa for 3, 7, 15 and 30 days
were; 75.5%, 69.25%, 29.75 % and 19.25% respectively, While the
amounts recovered from media inoculated with Bacillus mycoides were;
48.75%, 46.25%, 39.25 % and 28.25% following the same order. On the
other hand, the respective amounts recovered from media inoculated with
Bacillus cereus were; 45 %, 32.5 %, 30.5 % and 19.75% at 3, 7, 15 and
30 days, respectively. Despite the significant drop in the starting material,
no metabolites were detected in Bacillus cultures while only N-(1-
ethylpropyl)-3-methyl-2, 6-diaminobenzine was detected in P. aeruginosa
culture indicating the capability of these microorganisms of complete
mineralization of pendimethalin. Pendimethalin biodegradation by the
three types of bacteria followed a biphasic model with faster rate of