Abstract
Abstract Background Benzo(a)pyrene (BaP), a high molecular weight pentacyclic aromatic hydrocarbon, is a priority pollutant of extreme concern. Bacillus subtilis BMT4i (MTCC 9447) degrades BaP through chromosomally encoded pathway. Nevertheless, inadequate information is available on BaP degradation pathway in genus Bacillus despite of its species being shown as potent BaP degrader. The objective of this study was to elucidate BaP degradation pathway in B. subtilis strain BMT4i by identifying metabolites through UHPLC-MS. Materials and methods Batch experiments were conducted to characterize metabolic pathway of BaP in the bacterium B. subtilis BMT4i. The metabolites were separated and characterized by UHPLC-MS. Results The major intermediates of BaP metabolism that had accumulated in the culture media after 15 days of incubation were benzo(a)pyrene-11,12-epoxide, 7,8,9,10-tetrahydrobenzo[pqr]tetraphene-7,8,9,10-tetraol, benzo(a)pyrene-cis-7,8-dihydrodiol, 8-carboxy-7-hydroxy pyrene, chrysene-4 or 5-carboxylic acid, cis-4-(8-hydroxypyrene-7yl)-2-oxobut-3-enoic acid, hydroxymethoxybenzo(a)pyrene and dimethoxybenzo(a)pyrene. Among above, 8-carboxy-7-hydroxy pyrene, chrysene-4 or 5-carboxylic acid, and cis-4-(8-hydroxypyrene-7yl)-2-oxobut-3-enoic acid are ring cleavage products of BaP. Conclusion The identified metabolites indicated that BMT4i initially oxidized BaP with monooxygenases and dioxygenases at C-11,12 or and C-7,8 and C-9,10 positions, suggesting operation of multiple pathways for BaP degradation in B. subtilis. Further studies are essential to find out whether the entire biodegradation process in B. subtilis results into metabolic detoxification of BaP or not.
Highlights
The identified metabolites indicated that BMT4i initially oxidized BaP with monooxygenases and dioxygenases at C-11,12 or and C-7,8 and C-9,10 positions, suggesting operation of multiple pathways for BaP degradation in B. subtilis
Benzo(a)pyrene (BaP), a high molecular weight pentacyclic aromatic hydrocarbon, is a priority pollutant found in air, water, and soil [1,2,3]
The present study reports the presence of eight different metabolites including ring cleavage products suggesting functioning of multiple degradation pathways involving dioxygenases and monoxygenase as the initial attacking enzymes
Summary
Benzo(a)pyrene (BaP), a high molecular weight pentacyclic aromatic hydrocarbon, is a priority pollutant found in air, water, and soil [1,2,3]. Mycobacterium vanbaalenii PYR-1 degraded BaP to several dihydrodiols and one ring-cleavage product, 10-oxabenzo [def] chrysene-9-one [18]. Growth of S. yanoikuyae JAR02 on BaP yielded benzo(a)pyrene-cis 7,8-dihydrodiol and benzo(a)pyrene-cis 9,10-dihydrodiol in addition to pyrene-8-hydroxy-7-carboxylic acid and pyrene-7-hydroxy-8-carboxylic acid as novel ring-cleavage metabolites [21]. These reports suggested involvement of dioxygenase and monooxygenase which incorporate two or one oxygen atoms into the aromatic nucleus forming cis-dihydrodiols and trans-dihydrodiols, respectively as initial ring cleavage enzymes in BaP degradation pathway. The objective of this study was to elucidate BaP degradation pathway in B. subtilis strain BMT4i by identifying metabolites through UHPLC-MS. Results: The major intermediates of BaP metabolism that had accumulated in the culture media after 15 days of incubation were benzo(a)pyrene-11,12-epoxide, 7,8,9,10-tetrahydrobenzo[pqr]tetraphene-7,8,9,10-tetraol, benzo(a)pyrene-cis-7,8-dihydrodiol, 8-carboxy-7-hydroxy pyrene, chrysene-4 or 5-carboxylic acid, cis-4-(8-hydroxypyrene-7yl)-2-oxobut-3-enoic acid, hydroxymethoxybenzo(a)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
