Property And Mechanism Of Pyrene Degradation By Brevibacillus Brevis

Polycyclic aromatic hydrocarbons( PAHs) are a kind of ubiquitous persistent organic pollutants and toxicants existed in environment. Biodegradation is a primary means to eliminate PAHs pollution. This paper conducted aerobic bidegradation of pyrene utilizing Brevibacillus brevis, a strain with high degradation performance isolated from Guiyu e-waste dismantling area.The degradation condition, influence of additional carbon resource, change of cellular activity under the stress of pyrene, metabolites and mechanism of pyrene degradation were investigated.Brevibacillus brevis has high degrading capacity, and the degradation efficiency of1 mg·L-1pyrene by 1 g·L-1biomass was 53% within 5 d. A molecular mechanics calculation revealed that glucose changed the geometrical structure of pyrene and promoted the degradation rate from 53% to 69% at a concentration of 20 mg·L-1on 5 d. B. brevis efficiently utilized 20mg·L-1glucose within 3 days. The periodic addition of glucose helped to highly activate the strain, which facilitated the utilization of pyrene and increased pyrene degradation rate within 15 d.In the degradation system, the toxicity of pyrene caused reactive oxygen species(ROS)accumulation rising in B. brevis cells. The short-term exposure of pyrene interfered with antioxidation and metabolic capacity of B. brevis, but the interference receded with time. The bacterial cells suffered mass mortality in 0~2 d, but would regain their vitality and reproduction in later days. Glucose effectively relieved the stress of pyrene on B. brevis and guaruanteed the metabolic activity and reproduction.The catalysis of intracellular enzyme primarily contributed to degradation, and the degradation rate of intracellular enzyme excreted from B. brevis reached 50% for 12 h. Four hydroxy metabolites were detected in pyrene degradation, respectively 1-hydroxy-pyrene,9-phenanthrol, α-naphthol and β-naphthol. Three organic acids were also found, of which, oxalic acid was speculated as low molecule weight products of pyrene degradation. B. brevis released Na+、Cl-、 PO43-to the medium and absorbed K+、SO42-.The spores of B. brevis were extracted to conduct degradation experiment. The germination of spores in MSM was 1.5×108·L-1per sample, which was capable of degrading 15% of pyreneat 1 mg·L-1within 5 d.