Mechanism Of Adsorption Of Dibutyl Phthalate By Lactobacillus Acidophilus NCFM

Excessive amounts of dibutyl phthalate(DBP)can cause many food safety problems and endanger human health.Lactobacillus acidophilus NCFM is a commercial probiotic that has many physiological functions,such as anti-cancer and anti-mutation activities.It has been proven that strain NCFM has an adsorption effect on DBP.To explore the mechanism of the physical and chemical factors involved in the adsorption of plasticizer by Lactobacillus,strain NCFM and DBP were selected and binding analysis and molecular simulations were employed.The adsorption rate of DBP was determined by high performance liquid chromatography.To observe the change of functional groups,Fourier transform infrared spectroscopy(FTIR)was employed,and isothermal titration calorimetry(ITC)was used to determine the reaction constant and thermodynamic coefficient during the adsorption process.The materials were constructed by Materials Studio.The system was simulated and the intermolecular forces were calculated.Concurrently,the adsorption site was determined by the radial distribution function(RDF),and the free volume fraction(FFV)was used to observe the diffusion behavior.The relationship between physical and chemical factors and adsorption rate was analyzed by interaction energy,intermolecular force,adsorption site,diffusion behavior and cell surface structure.The results are as follows:(1)The adsorption process of DBP by L.acidophilus NCFM was an exothermic process and involved physical adsorption.The reaction constant K=5.84 × 104,enthalpy change ? H=-7.5 × 103 kJ/mol,entropy change ? S?67.0 kJ/K.(2)In the adsorption process of DBP by L.acidophilus NCFM,the main forces included van der Waals,electrostatic,and hydrogen bonding forces.Saccharide substances,such as cell wall peptidoglycan,were the main adsorption sites,and the influence of each adsorption site did not change with the changes in temperature,concentration,and urea content.(3)Several factors affected the adsorption rate of DBP by L.acidophilus NCFM.First,when the cell surface was negatively charged,it was favorable for adsorption.Second,stronger hydrophobic interaction resulted in better adsorption.Third,lower free volume fraction of the system resulted in better adsorption.Lastly,rougher cell surfaces had more exposed adsorption sites,which increasingly favored adsorption.The experimental results were consistent with the molecular simulation data,and were highly accurate.The findings indicate the potential use of lactic acid bacteria to adsorb carcinogens.