Isolation and Characterization of Polyaromatic Hydrocarbons PAHs Degrading Dioxygenase Enzyme from Environment for Effective Bioremediation

Abstract

The polyaromatic hydrocarbons (PAHs) emissions are one of the important factors in newlineworldwide pollution. PAHs are released in the environment through incomplete newlinecombustion of fossil fuels, forest fires, crude oil spill, industrial smokes, coal, and newlinetobacco smoke. Many PAHs are known as potent carcinogens and/or mutagens via newlineDNA adduct formation. Earlier, several physico-chemical methods have been used to newlinedegrade PAHs from the environment. The prime objective of the current study was to newlinefind out an efficient PAHs degrading microbial strain and to isolate an enzyme from newlinethis strain that catalyzes the PAH degradation for effective bioremediation. newlineSix bacterial isolates from industrial effluents were purified using serial newlineenrichment technique and their pyrene degrading potential on pyrene supplemented newlinemineral salt medium was assessed. 16S rRNA gene sequence analysis showed that they newlinebelong to four bacterial genera, namely Acinetobacter, Bacillus, Microbacterium, and newlineOchrobactrum. Among these purified isolates, Bacillus megaterium YB3 showed newlineconsiderably good growth and was further evaluated for its pyrene-degrading newlineefficiency. The maximum growth for YB3 was observed at 30°C and pH 7.0 while least newlinegrowth was observed at 55°C and pH 4.0. At temperature (30°C) optimum and pH newline(7.0) conditions, B. megateriumYB3 could grow faster at 100 mg l-1 pyrene in 3 days newlinewhile it also showed relatively good growth at 300 and 500 mg l-1 pyrene concentrations newlinein 4th and 5th days, respectively. The B. megaterium YB3 could degrade 72.44% of 500 newlinemg l-1 pyrene within 7 days of its incubation. GC MS analysis of the ethyl acetate newlineextracted fractions detected two relatively less/non-toxic metabolic intermediates newlinewhich hinted that the B. megaterium YB3 follows phthalate pathway for pyrene newlinedegradation. newlineB. megaterium YB3 tested positive for catechol 1, 2-dioxygenase and aromaticring- newlinehydroxylating dioxygenase (RHD) indole-indigo conversion assays. Catechol 1 2- newlinedioxygenase was isolated from B. megaterium YB3 and purified using ion-exchange ...