Isolation, Identification And Degradation Characteristics Of Bisphenol A Degrading Strain

A bisphenol A(BPA) degrading strain B-16 was isolated from compost leachate of municipal solid waste. According to the morphological characteristics, physiological and biochemical, and sequence analysis of 16S rDNA, the strain was identified preliminarily as Achromobacter xylosoxidans.By tests in shaking flasks, the effects of the conditions of growth was studied, and it was determined that the optimum conditions were inoculum amount 0.6%, pH 7.0, shaking velocity 200r/min, filling-liquid volume 200mL and 30℃. Under these conditions, when the initial concentrations were low (3mg/L,5mg/L,10mg/L), the degradation reaction tallied with one order kinetic characteristic, while when in high initial concentrations(20mg/L,50mg/L), the degradation reaction can't be described by one order kinetic characteristic. When the initial concentration was 10mg/L, the degradation rate was maximal, and it was 46.93%.It was observed that when the initial concentrations were 3mg/L,5mg/L,10mg/L,20mg/L,50mg/L, the growth of the bacteria in the BPA cultures reached the maximum level at about 1.5d,2d,3d,3d,3d, respectively. Thereafter, the bacterium amount decreased markedly. The lag phase of bacterial growth was unconspicuous or relatively short and the BPA was degraded rapidly in 3d after inoculation in each initial concentration. The logarithmic phase of 10mg/L and 20mg/L was longer than those of other concentration, and the logarithmic phase of 50mg/L was shortest.Analysis of metabolic intermediate and possible reaction pathways was performed with LC-MS technique. In this study, BPA was firstly metabolized to form three intermediates p-hydroxyacetophenone, p-hydroxybenzaldehyde and p-isopro- penylphenol. Subsequently, there are three primary pathways: pathways 1. in which p-hydroxyacetophenone was oxidated to form p-hydroxybenzoic acid which then converted to carbon dioxide and biomass, pathways 2. in which p-hydroxybenzal -dehyde was converted to carbon dioxide and biomass directly, pathways 3. in which p-isopropenylphenol was converted to p-hydroquinone by ?OH radicals attack and that mineralized by cells. Apparently, the relative amounts or activities of the enzymes involved in the BPA degradation pathway were sufficiently different.