Biodegradation of pesticide profenofos by the free and immobilized cells of Pseudoxanthomonas suwonensis strain HNM

Profenofos is an organophosphate pesticide used extensively in agriculture to control pests. A bacterium capable of degrading profenofos was isolated from pesticide-contaminated soil samples and identified as Pseudoxanthomonas suwonensis strain HNM based on its morphological and biochemical characteristics and phylogenetic analysis of 16S rRNA gene sequences. 4-Bromo-2-chlorophenol was identified as a metabolite of profenofos degradation by HPLC and GC-MS analysis. The organism degraded profenofos by hydrolysis to yield 4-bromo-2-chlorophenol which was further utilized as carbon source for growth. The organism utilized various organophosphate pesticides such as temephos, quinalphos, and chloropyrifos as carbon sources. The optimum conditions for degradation of profenofos by P. suwonensis strain HMN were found to be at pH 7 and 30 degrees C. We have investigated the rate of degradation of profenofos by the free and immobilized cells of P. suwonensis strain HNM in various matrices such as sodium alginate (SA), sodium alginate-polyvinyl alcohol (SA-PVA), and SA-bentonite clay. The rate of degradation of 3 and 6mM profenofos by the freely suspended cells were compared with that by immobilized cells in batches and semi-continuous with shaken cultures. The SA-bentonite clay-immobilized cells showed higher rate of degradation of 3 and 6mM profenofos then freely suspended cells and cells immobilized in SA and SA-PVA. The SA-bentonite clay-immobilized cells of P. suwonensis strain HNM could be reused for more than 32 cycles without losing their degradation capacity. Thus, the immobilized cells are more efficient than freely suspended cells for the degradation of organophosphate pesticide contaminated water.