The Preliminary Study On The Of The Modified Magnetic Graphene Oxide Immobilized Lipase By Span/Tween

Lipase(EC 3.1.1.3),with mild reaction conditions,high specificity,high catalytic efficiency and environmental friendliness,has been widely used in chemical synthesis and biodegradation.The enzyme stability and repeatability can be improved after fixation with the carrier.Graphene oxide is a two-dimensional structure of single atom with large surface area,which is beneficial to the adsorption of enzymes on the surface of the carrier and the mass transfer of substrate and products.Based on graphene oxide,preparation of magnetic oxide graphene(MGO)by chemical coprecipitation and modified by Span/Tween surfactant,and then used for immobilized lipase OF,preliminary discussion Span/Tween modification for the effect on the catalytic properties of the magnetic oxide graphene immobilized enzyme.With different surfactants modified carrier immobilized enzyme,the modified carriers were found to improve the protein load and the recovery of specific activity.Compared with the specific activity of lipase OF(12.90U·mg-1),the specific activity of Span60/MGO-OF was 36.31 U mg-1,which was the highest in the specific activity recovery rate,reaching 281.5%.For the adsorption of enzyme protein,the carrier Span40/MGO has the highest load capacity of protein,reaching 114.36 mg g-1support.After measuring the kinetic parameters of the immobilized enzyme,found that the modified carrier of the immobilized enzyme Km is generally reduced,the Vmax and Km of the free enzyme is 24.95 U·mg-1,1.21 mmol·L-1,while the Vmax and Km of the Span40 modified carrier immobilized enzyme were changed to 43.07 U·mg-1,0.46 mmol·L-1,thus the catalytic efficiency(Kcat/Km)was increased from 24.95 s-1/mM-1 to 93.56 s-1/mM-1.The pH and temperature adaptability of immobilized enzyme and thermal stability are also improved.After five cycle number,the immobilized enzyme remained about 30.0%of its initial activity,and remained 56.1%of its initial activity after 31 days that storage at room temperature.Compared with the catalytic properties of the lipase OF,MGO-OF and Span40/MGO-OF,it found that immobilized enzyme had better pH,temperature adaptability,and the thermal stability was improved.After repeated use 5 times,the relative activity of Span40/MGO-OF still remain the relative activity of 30.0%.After 31 days storaged at room temperature,the relative activity of Span40/MGO-OF still remain 56.1%,that showed excellent storage stability.In addition,by the technology of scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),Thermogravimetric analysis(TGA),the properties of modified bentonite and immobilize lipase were studied.It's found that the magnetic Fe304 nanoparticles and graphene oxide was successfully prepared,surfactant successful packages on the carrier surface and the lipase OF was successful immobilized on the modified carrier.Adopted the Fourier transform infrared spectroscopy(FT-IR)analyed the secondary structure of immobilized enzyme and Contact Angle analyed that explored the mechanism between modified carrier and lipase.It's found that the hydrophobic carrier can significantly increase the catalytic activity of lipase.The reason that the hydrophobic carrier can change the conformation of lipase,and opened the "lid" on the active center structure.