Abstract

Many aromatic hydrocarbons are known to be toxic and carcinogenic to humans and their contamination of soils and water bodies is of a great environmental concern. Hence microbial degradation of these hydrocarbons to less toxic compounds has become a vital tool in making the environment safe for humans as well as other life forms. The biodegradation of a low molecular weight (LMW) Polycyclic Aromatic Hydrocarbons (PAHS) consisting of a mixture of a Phenanthrene (Phe), by bacteria enriched from industrial waste water samples was extensively investigated. The samples from which the bacteria were enriched were randomly collected from three different points at a local brewery in Shuangyang County, Jilin province, China. These samples were designated by the letters: HY, YY and WS. The Bacteria were enriched using Mineral salt Medium-MSM (K₂HPO₄, KH₂PO₄, MgSO₄∙7H₂O, NaCl, FeSO₄∙7H₂O, NH₄NO₃, CaCl₂∙2H₂O, C₆H₁₂O₆). The pH and optical density (ODλ) readings after five consecutive weeks (five transfers) were determined. The OD readings revealed that the sample HY degraded Phe the most, followed by the sample YY. The sample WS was least degraded Phe. This indicated that there were more bacteria in HY exhibiting synergism in degrading Phe than YY. Six pure bacteria were isolated from the samples, and among these, WS111 had the highest bacterial density/OD value. The genomic DNA of the six bacteria was extracted, and PCR (Polymerase Chain Reaction) analysis and 16SrDNA of the bacteria were identified based on similarity using the National Center for Biotechnology Information (NCBI) online standard BLAST (Basic Local Alignment Search Tool) program (http://www.ncbi.nlm.nih.gov) as: HY1 = Alcaligenes sp., HY32 = Phyllobacteriaceae sp., HY52 = Pseudochrobactrum sp., YY31 = Pseudomonas sp., YY41 = Alcaligenes sp., and WS11 = Sphingobacterium sp. These bacteria (WS111, HY32 and HY 52) degraded Phe. LMW fluoranthene (flo), and HMW Pyrene (pye), and Chrysene (chy) on mineral salt agar medium were also degraded by these bacteria. The catechol was formed by bacteria as an intermediate, and emulsions and foams were formed when added to crude oil (petrol) and also a clearer zone/halo was formed by the bacteria YY31 when added to blood agar medium compared to the others.

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