Biosorption of diethyl phthalate ester by living and nonliving Burkholderia cepacia and the role of its cell surface components

- Living and nonliving cells achieved more than 80% of maximum sorption within 30 min.
- Nonliving cells had greater biosorption capacity for DBP than the living cells.
- DBP biosorption by B. cepacia was mainly attributed to passive surface binding.
- The optimum pH for DBP adsorption by living and non-living cells was both 6.0.
- Cell wall lipids, proteins or peptidoglycan played key roles in the DBP biosorption.

In this study, the dibutyl phthalate (DBP) binding properties of a DBP-tolerant bacterium (B. cepacia) were characterized in terms of adsorption kinetics and isotherm. Living and nonliving cells both exhibited rapid removal of DBP, achieving more than 80% of maximum sorption within 30 min of contact and reached the equilibrium after 3 h. The adsorption isotherms were well fitted with the Sips model and the nonliving cells have greater biosorption capacity and affinity for DBP than the living cells. Furthermore, the absence of an active mechanism dependent on metabolism implied that the DBP bioaccumulation by living cells was mainly attribute to passive surface binding. The optimum pH for DBP adsorption by living and nonliving cells were both observed to be 6.0. The biosorptive mechanism of DBP binding by B. cepacia was further confirmed by FTIR analysis and various chemical treatments. FTIR results indicated that the phosphate and CH2 groups on B. cepacia were the main bounding sites for DBP. Furthermore, 2.28, 2.15, 1.93 and 0.87 g of pretreated cells were obtained from 2.40 g of native cells via extracellular polymeric substances (EPS), superficial layer-capsule, lipids components and cell membrane removal treatments, respectively. Total binding amount of DBP on the native cells, EPS-removed cells, capsule-removed cells, lipids-extracted cells and membrane-removed cells were 26.69, 24.84, 24.93, 16.11 and 10.80 mg, respectively, suggesting that the cell wall lipids, proteins or peptidoglycan might play important roles in the sorption of DBP by B. cepacia. The information could be applied in understanding on the mobility, transport and ultimate fate of PAEs in soil and related environment.