Screening Of Highly Efficient Degradation Bacteria Of Di-N-amyl Phthalate And Its Degradation Characteristics

Di-n-amyl phthalate(DAP)is a common environmental pollutant and is well known for its endocrine disrupting activities.Widely use of the plastics and pesticides in agriculture have resulted in DAP pollution in soils and water.In this study,a Di-n-amyl phthalate(DAP)degrading bacterial was isolated from activated sludge.It could utilize DAP as sole carbon and energy sources for growth.According to its phenotypic characteristics,physic-biochemical characteristics and 16S rRNA gene sequence analysis,strain was identified as comamonas testosteroni and named as LS1.The strain LS1 grew well in LB liquid medium.After 8h,it entered into the logarithmic growth and 30-40h it entered the stable growth period.The optimum temperature and pH for the growth of strain LS1 was 30℃ and pH=7.0～8.0,respectively.Less liquid volume was better for the growth of the strain LS1.More dissolved oxygen in the water was benefit for the growth of the bacteria.The strain could not utilize organic carbon source such as fructose,xylose,sucrose,maltose or glucose;For nitrogen sources,LS1 could highly utilize peptone and followed are ammonium nitrogen and nitrate-N.LS1 could barely utilize nitrite-N or urea.The strain LS1 with salt tolerance could grow well in the range of 0～15g/l NaCl concentration which had outstanding advantages in wastewater treatment applications.The strain LS1 could completely degrade 200 mg·L-1 DAP in 48 h in MSM culture;when cultured in the medium,the OD600 increased during the degradation process,which indicated that the strain could use DAP as the sole carbon source for growth.The optimum temperature and pH for DAP degradation by strain LS1 were 30℃ and pH range from7.0 to 8.0,respectively,which was the same as its growth characteristics.The lower initial concentration,the easier utilization of DAP by the strain.Generally,the strain could utilize a high concentration of DAP.LS1 could utilize Phthalic acid but not other PAEs as the sole carbon source for growth.A 1000 bp DNA fragment was obtained from the strain LS1 by PCR amplified and clone.The degradation intermediates of DAP was identified as phthalate acid(PA).The metabolites during the degradation were detected by LC-MS.The pathway of DAP degradation was DAP to PA before its mineralization.