Solubilization And Biodegradation Enhancements Of Phenanthrene By Sulfobutylether-?-cyclodextrin

Public concerns on polycyclic aromatic hydrocarbons(PAHs)have grown rapidly due to recognition of their toxicity,carcinogenicity,and teratogenicity.Microbial remediation is preferred as a clean and cost-effective method for restoring environments polluted by PAHs.However,the aqueous solubility of PAHs is the main limited factor for microbial degradation,because microbes only can degrade the part which dissolved in water.At present,the pollution situation of PAHs in China is not optimistic.How to increase the solubility of PAHs in water,improve their biodegradation rate,and then removing PAHs in the environment more effectively are of great significance.Solubilizing agents,which include surfactants and cyclodextrins,have been used widely to enhance water solubility of PAHs.Compared with surfactants,cyclodextrins have advantages of non-toxicity and biodegradability.In this paper,SBE-?-CD was selected as PAHs solubilizer from 20 cyclodextrins and their derivatives,based on molecular docking results.Hydroxypropyl-?-cyclodextrin(HP-?-CD)was used as contrast and phenanthrene was chosen as a representative of PAHs.And then,the solubilization and biodegradation enhancements of phenanthrene by sulfobutylether-?-cyclodextrin(SBE-?-CD)were studied.The solubilization effects of SBE-?-CD on PAHs were investigated firstly.In addition,the mechanism of SBE-?-CD solubilization process was studied from the perspective of solubilization influencing factors(temperature,time and inorganic salt species)and SBE-?-CD-phenanthrene inclusion characterization.Furthermore,degradation experiment of phenanthrene was conducted to investigate whether biodegradation of phenanthrene can be enhanced by SBE-?-CD.The results showed that solubilization effect of PAHs(phenanthrene,pyrene and fluoranthene)with SBE-?-CD addition were obviously better than that of HP-?-CD.The inclusive ratio between SBE-?-CD/HP-?-CD and phenanthrene/pyrene/fluoranthene are 1:1.Experiments showed that time and inorganic ions have little effect on solubilization capacity of SBE-?-CD.It was found that the proper warming was beneficial to the solubilization of phenanthrene.The result of thermodynamic analysis demostrated the hydrophobic interaction and the release of high enthalpy water molecules in the cyclodextrin cavities are the intrinsic solubilization driving force of SBE-?-CD.On the other hand,characterization experiment of inclusion suggestd that phenanthrene was binded to the narrow ends of SBE-?-CD and tilted at a certain angle.Pseudomonas sp.JM2 was obtained from activated sludge and was used for degrading phenanthrene.And then,degradation experiment of phenanthrene was conducted in solution systems and soil systems respectively.The degradation experiment of phenanthrene in solution system showed that,after 10 h,the residual phenanthrene concentration was 95.12 mg/L when JM2 exists only.The concentration of phenanthrene decreased from the initial 150 mg/L to 3.04 mg/L with addition of SBE-?-CD.Compared with 24.92 mg/L,which is the residual phenanthrene concentration with addition of HP-?-CD,SBE-?-CD has a better biodegradation promotion effect(The concentration of phenanthrene in the blank control group of sterilized bacteria was 135.03mg/L after subtracting background loss).The degradation experiment of phenanthrene in soil system also showed that,after 5d the biodegradation rate of phenanthrene in the presence of SBE-?-CD was 9.3% and 58.97% higer than the group which added HP-?-CD and only contains degrading bacteria(The concentration of phenanthrene measured at 5 d in the blank control group of sterilized bacteria was 114.08 mg/L).Based on above results,it can be determined that SBE-?-CD has a good solubilization and biodegradation effect on phenanthrene.SBE-?-CD can be a promising additive in bioremediation of PAHs contaminated water and soil.