Research On The Characteristics And The Mechanisms In Remediation Of BaP-Pb²⁺ Combined Pollution System By Brevibacillus Brevis

A strain Brevibacillus brevis which could tolerate heavy metals lead （Pb）, copper （Cu）,zinc （Zn） and cadmium （Cd）, and could degrade benzo[a]pyrene （BaP） was isolated fromthe contaminated sediments. The study on the degradation of BaP and the adsorption ofheavy metals was carried out in single and combined pollution systems. The changes incell surface of B.brevis were investigated, and the properties and biodegradation pathwaywere also discussed.B.brevis tended to utilize glucose and ammonium sulfate as carbon and nitrogen sources.It could utilize BaP as a sole carbon and energy source as well. Addition of salicylic,succinate and phthalate showed no obvious positive effect on BaP biodegradation.B.brevis could tolerate a wide pH and temperiture ranges, the optimum conditions for BaPdegradation was pH7and25℃. With the increase of B.brevis dosage, the degradationefficacy displayed an initial increasing trend and then came to a plateau. And the increaseof BaP concentration from0.1to10mg·L^-1led to the enhancement of BaP degradationamount. The BaP degradation could be up to51.35%in the conditions pH7and25℃.Heavy metal ions Pb²⁺, Cu²⁺, Zn²⁺and Cd²⁺inhibited the degradation of BaP. Cell wall ofB.brevis could adsorb both BaP and Pb²⁺. Parts of pollutants which adsorbed on the cellsurface would be transported into cells and biodegraded.Surface of B.brevis could be changed while degrading BaP. With the toxic effect, thesurface of B.brevis wrinkled and depressed, the nucleus area blurred at the first. Then theintracellulat substances outflow, the hole cell deflated, parts of cells become empty shells,and the activity of cell decreased over time. The changes were more serious and obvious in combined pollution systems.The degradation of BaP by B.brevis is related to groups-OH, C=C, C=O,-CH3,-CH2andphenol either in single or combined contamination systems. The first step of BaPdegradation is loop open and the generation of dihydrodiol. In single pollution, thereaction would go on and generate3-rings PAHs or diphenyl while in combined pollutionsystem only3-rings PAHs was observed. The low-ring PAHs then decompose into smallmolecules.