Study On Pickering Emulsions Stabilized By Enzyme-loaded Colloidosomes For Interfacial Catalysis In Biphasic System

Enzymes are the core and key of biocatalysis,producing compounds needed by humans through high efficiency and selective catalysis under mild and sustainable conditions.Herein,in the water/butanol system,lipase and SiO₂ nanoparticles are dispersed in the water phase,and as the diffusion of water to butanol,lipase-loaded hollow colloidosomes(LHCs)are formed.Since lipase molecules cannot cross the water-butanol interface,they are efficiently confined on the colloidosomes shell with the process of SiO₂ nanoparticles assembly at the interface.The encapsulation rate is as high as 95.2%,and the loading amount of lipase is 44.4 mg·g^-1(lipase/(lipase+SiO₂)).Moreover,the colloidosomes can stabilize Pickering emulsion(particle-stabilized emulsions)by adjusting the wettability of LHCs for the enzymatic catalysis at the oil-water interface.This thesis explored the formation mechanism of LHCs and the mechanism of Pickering emulsion stabilized by enzyme-loaded colloidosomes and the application of the biphasic interfacial catalysis are studied.(1)In order to explore the catalytic performance of LHC,it is used to enhance the interfacial biocatalysis of the oil-in-water(O/W)Pickering emulsion.Due to the amphiphilic lipase confined in the shell changed the wettability of colloidosomes,LHCs can serve as a stabilizer of Pickering emulsion without surface modification.Taking the hydrolysis of tributyrin by lipase as the research object.The hydrolysis results show that the enzyme activity of LHCs is 6.67 times higher than that of the conventional biphasic system,which is caused by many factors such as the increase of the oil-water interface area by the Pickering emulsion form and the higher contact probability between lipases and substrates due to the hollow structure.In addition,LHCs has good recyclability,and 80.4%of the initial enzyme activity is still maintained after 10 cycles,and the morphology of the colloidosomes remains intact.Moreover,LHCs possess nanochannels between SiO₂ nanoparticles,which help the mass transfer of the substrate/product,making LHCs have a higher mass transfer coefficient(6.511×10^-4 s^-1).This approach provides a new idea for immobilized enzyme,and provides a high-performance and robust platform for efficient bio-transformations in a green manner.(2)In order to further expand the application of LHCs,lipase-loaded colloidosomes with customizable wettability is designed for Pickering emulsion interface,providing a simple and feasible scheme for enzymatic production of biodiesel.By changing the mass ratio of hydrophilic and hydrophobic nanoparticles during the formation of LHCs,biocatalysts with different wettability are prepared and used in the ester synthesis reaction at the oil-water interface.The results show that the catalytic effect of hydrophobic LHCs(11.94 U·m L^-1)is 8.18times that of conventional biphasic system(1.46 U·m L^-1).Moreover,it is also better than amphiphilic and hydrophilic LHCs(10.98 U·m L^-1,10.10 U·m L^-1),because methanol in the water phase can cause partial inactivation of protease,thus the catalysis effect of LHCs biased toward the oil phase is better.Under the stable emulsion system of hydrophobic LHCs,the yield of biodiesel can reach up to 85.43%and can still maintain 96.44%of the initial enzyme activity after 10 cycles(8 h per cycle).It provides an efficient,green and sustainable way for the industrial-scale Pickering emulsion interface biocatalysis process.