Study Of Bisphenol-A-degrading Endophytic Bacteria From Surbmerged Plants And Their Degrading Mechanisms

As a typical environmental endocrine disruptor,bisphenol A is widely used in chemical industry.It is taken into the water environment through industrial wastewater and other wastes in the process of production and using,which leads to all kinds of water pollution all around the world.Bisphenol A in water is also a potential threat to the health and stabilization in water ecosystem.As representatives of submerged plants,Myriophyllum verticillatum and Elodea canadensis are taken as pioneer plants in the restoration of water body playing an important role in water purification.Meanwhile,endophytic bacteria which are distributed in the host plant,can not only promote plant growth,but also enhance the host plant on degradation of environmental pollutants so that reduce the enrichment of toxic pollutants in the plant body.It is necessary to carry out researches about isolation,identification,degradation properties and mechanisms of endophytes from submerged plants,namely M.verticillatum and E.canadensis.It is useful to have a good knowledge of the fate of bisphenol A in water body and illuminate the bio-remediation mechanisms of macrophytes.It is of great significance to the bio-remediation of bisphenol A in the polluted water.This article firstly isolated endophytic bacteria from the submerged plants which had ability of utilizing bisphenol A.The degrading properties and mechanisms of the isolates were also studied,which would lay a theoretical basis for managing the pollutant of bisphenol A in the environment.The results were as follows.(1)Endophytic bacterial strain Mv32,capable of utilizing bisphenol A as source of carbon for growth,was isolated from M.verticillatum.The degrading conditions for strain Mv32 were optimized by tests in shaking flasks and orthogonal tests.The results showed that the optimal conditions for the degradation on BPA of strain Mv32 at initial concentration of 10 mg/L were 1%inoculum size,initial pH 7 and 25?.Based on the above optimal conditions,the maximum optical density(600 nm)of strain Mv32 increased to 0.22 and 47.17 ± 1.22%BPA with an initial concentration of 10 mg/L was removed in 3 days.Strain Mv32 was identified as Paenibacillus sp.based on morphological characteristics and 16S rRNA gene sequence analysis.At the same time,the removal of water sample from south lake by strain Mv32 was studied with removal efficiency of bisphenol A 95.78 ± 0.31%.(2)Endophytic bacterial strain Ec18,capable of utilizing bisphenol A as source of carbon for growth,was isolated from E.canadensis.The results of degrading conditions showed that the optimal conditions for the degradation on BPA of strain Ec18 at initial concentration of 10 mg/L were 2%inoculum size,initial pH 6 and 30?.Based on the above optimal conditions,the maximum optical density(600 nm)of strain Ec18 increased to 0.23 and 40.59 ± 0.60%BPA with an initial concentration of 10 mg/L was removed in 3 days.Strain Ec18 was preliminarily identified as Methylobacterium sp.based on morphological characteristics and 16S rRNA gene sequence analysis.Furthermore,the removal of water sample from south lake by strain Eel 8 was studied with removal efficiency of bisphenol A 68.47 ± 1.91%.(3)The possible enzymes involved in bisphenol A degradation were discussed through the effects of inhibitors on degradation rate.The results of inhibitors experiments provided the evidences that cytochrome P450 and laccase were involved in BPA metabolism and transformation.Besides,partial sequence of laccase from strain was amplified with degenerate primers named CulAF and Cu2R.The results showed that amino acid alignment result of the sequence was 79%identity with reported laccase amino acid sequences.Presumably,the sequence was a new bacterial laccase gene.