Studies On Biodegradation Characteristic Of DEP By Three Newly Isolated Strains Of Pseudomonas

Di-ethyl phthalate,a type of plasticizer,is one of the most commonly used phthalate esters in our daily life.Environmental pollution caused by DEP has become a serious concern all over the globe.They are abundantly present in the frequently used daily items like plastics,cosmetics,etc.and are known to cause not only endocrine hormone disruption but also teratogenic,hepatotoxic and carcinogenic effects in humans as well as other animals.Researches disclose that DEP is responsible for destroying the nervous system and reproductive organs of males and females.Hence,it has been regarded as one of the solemn pollutants by the U.S.Environmental Protection Agency.Two types of environmental degradation of DEP are present;biotic and abiotic,among these,biotic processes mediated by the microorganisms is the primary way of biodegradation of DEP in aquatic and terrestrial systems,such as sewage,soils,sediments,sludge and surface waters.Abiotic processes like hydrolysis and photolysis are relatively slow and are not the main routes of degradation of DEP.Studies have shown that longer chains phthalate esters are difficult to metabolize than shorter chains.Microorganisms can metabolize DEP into simpler forms such as DMP,PA which ultimately are converted either into oxaloacetate or acetate depending upon the availability of molecular oxygen.Ultimately,these compounds can be utilized by the microbes as the substrate in TCA,acetate fermentation,?-oxidation or other pathways ensuring their survival.Inspiring from this,bioremediation has widely purposed for the removal of PAEs from the highly contaminated sites by the many research scientists.This study also aimed to isolate,characterize and screen the most efficient bacterial strains possessing the abilities to metabolize DEP as the sole source of carbon as well as energy from the sediments of extremely polluted South lake.Based on the morphological,biochemical,physiological and 16S rDNA gene sequencing,three efficient new bacterial strains;Pseudomonas sp.strain CCNU-SK1,P.denitrificans strain CCNU-SK3,and P.putida strain CCNU-SK2 were isolated and identified.This is probably the first study regarding the biodegradation of DEP by newly isolated Pseudomonas sp.strain CCNU-SK1,P.putida strain CCNU-SK2 and P.denitrificans strain CCNU-SK3.Biodegradation of DEP was studied in various parameters such as temperature,pH,concentrations of DEP,NaCl,etc.The optimum growth and biodegradation of DEP were obtained at 28?,at pH 8,concentration of DEP(500 mg/L)and NaCl(1.5%)with half-life 10.19 hours in case of Pseudomonas.sp.strain CCNU-SK1.Likewise,the optimum conditions for the biodegradation of DEP by P.denitrificans strain CCNU-SK3 and P.putida strain CCNU-SK2 were 33?,pH 7,concentration of DEP(500 mg/L),NaC1(1.75%)with half-life 12.6 hours and 33?,pH 7,concentration of DEP(400 mg/L),NaCl(1.5%)with half-life 13.86 hours respectively.Strain CCNU-SK1 with lowest half-life period was the most efficient bacteria for biodegradation of DEP compared to other isolated strains.Results showed that more than 99.0%of all DEP were biodegraded within the 4 days of incubation by strain CCNU-SK2,strain CCNU-SK3,and strain CCNU-SK1.The complete utilization of(50 mg/L)DEP occurred within 24 hours by all the strains of Pseudomonas sp.They were capable of metabolizing not only DEP but also other PAEs like DEHP,DBP,DMP,PA,BBP,DOP.This versatility of Pseudomonas strains makes them potential candidates for PAEs biodegradation,and they can be used as the promising agents for the bioremediation processes in the PAEs contaminated sites in environmental settings.