Degradation Of Polycyclic Aromatic Hydrocarbon In Oil-water Two Phase System Strengthed By Interfacial Nanofibrous Enzyme Membrane

The enzyme catalytic reaction in oil-water two phase system has research andapplication value, but it also has many problems. Enzyme is stability in the aqueous phase,but the hydrophobic substrate exists in the organic phase and is limited solubility in water,so the substrate which form the speed limiting factors for water phase enzyme reaction.Another part of enzyme molecules on the oil-water interface, can contact with substrate intwo phase system at the same time, but the interface effect can easily cause enzymeinactivation, namely low enzyme activity at interface limits the enzyme reaction. Thispaper firstly prepared several new nanostructure interface fiber enzyme membrane carriers,the carriers could spontaneous distributed in the two phase interface. A model enzyme,laccase, was immobilized onto the interface nanofibers membranes, and was further appliedto catalyze the degradation of polycyclic aromatic hydrocarbons (PAH). The details in thisstudy were summarized as follows:Fristly, PU nanofibers with a uniform diameter of about270-300nm were prepared byeletrospinning. PU membranes added with5%w/w of lithium chloride (LiCl) couldincrease the adsorption ability of the hydrophilic molecular chitosan. Laccase immobilizedon PU membranes after modified by crosslinking. The immobilized condition wasoptimized as following: enzyme concentration of1.0mg/mL, glutaraldehyde concentrationof0.5%and the crosslinking time of3h. Under these conditions, enzyme loading of6.21mg protein/g-carrier was obtained. The hydrophilic modification could reduce the PUmembrane water contact angle (WCA) from120oto92.6o, the WCA of PU-enzymemembrane was90.1o.Secondly, as a template, chitosan induced hydrolysis of sodium silicate in solution forbiomimetic formation of SiO2nanoparticles. Under the condition of pH4.5, chitosansolution (0.002~0.2%w/w) and sodium silicate solution (45~100mM) mixed and preparednanoparticles size around150nm, the silicification reaction rate was found to closely obeythe fourth-order kinetics. The enzyme solution mixed with chitosan solution andpre-incubated1.5h, then the mixture solution was added to sodium silicate solution in thepreparation of silica nanoparticles embedding enzyme. The activity of immobilized laccase and manganese peroxidase (MnP) were67.96U/g-carrier and1.3U/g-carrier, and theimmobilized enzyme has high ultrasonic and organic solution stability. The PU nanofibersadsorbed with chitosan incubated in100mM sodium silicate solution to control theformation of SiO2-nanoparticles or coating. Compared with the crosslinking enzyme, theinterface stability and repeated use of embedding enzyme on nanofibers had significantlyimproved.Thirdly, through secondary electrospinning method, we prepared the double layersnanofibers contained both hydrophilic and hydrophobic layer, the hydrophobic layer wasPVDF and hydrophilic layer was nylon66. The immobilized enzyme activity onhydrophilic nylon66was12.34×10-3U/g. The layer of PVDF, because of its strongerhydrophobicity, had almost no ability of immobilized laccase. In the two phase system, theanthracene degragation rate was117.17mg/mg-protein*h by the immobilized laccase ondouble layers nanofibers.