Study On Cascade Reaction And New SERS Of Pickering Based On Interface Structure Of Protein-Regulated Emulsion

Modern food industry pays more and more attention to food safety and efficient production.However,the disadvantages of high energy consumption and high pollution in the process of production and processing have hindered the social and economic transformation.How to achieve safe and efficient production as well as subsequent rapid detection is the key research direction and frontier topic in the field of food processing and production.Pickering intelligent response emulsion has been widely used in fine chemical industry,fuel upgrading and other fields as a platform for streamlining the operation process.However,the application of the technology in the field of food and pharmaceutical industry is still very limited.The fundamental reason is that the development and mechanism of food grade response to Pickering emulsifier is still in the exploratory stage at home and abroad.Little is known about the mechanism of the reaction emulsion and the relationship between the structure and responsiveness of the emulsifier.Therefore,this paper focuses on the construction and interface regulation of protein-based response emulsion.The intelligent responsive Pickering emulsion system is constructed by controlling the protein adsorption to adjust the surface function of nanoparticles.Based on this system,the cascade catalytic reaction(PIC)with the advantage of simplifying the production process and the new practical SERS with fast cycle detection were realized.The Main results were shown as follows:(1)Construction of protein-based pH responsive emulsion for interfacial catalysisFirst of all,the pH responsive emulsion was successfully constructed using pure sodium caseinate(NaCas)as the sole emulsifier.Then we explored the universality and specificity of the system revealed the mechanism of NaCas regulating the steady/instability of the emulsion.Finally,the catalyst was introduced into the system to test the catalytic efficiency,separation and cyclicity.The emulsion could not only effectively cycle more than 100 times,but also maintain its pH response characteristics in saturated salt solution or sea water,and it also proved that the system could be widely applied to many kinds of oils.The excellent response ability of the system stems from the unique open conformation of NaCas and the hydrophobic and hydrophilic domains of block distribution.By adjusting the pH value,the amino acid terminal residues are protonated and deprotonated,thus driving the reversible emulsion/demulsification.In addition,phosphoserine clusters on NaCas can dynamically bind to positive ions and act as carriers to capture ions by forming a positive charge layer around the local micelles,which provides theoretical support for strong salt tolerance.NaCas has also been successfully applied to physical modification of organic and inorganic nanoparticles,so that traditional Pickering emulsions can be transformed into pH responsive Pickering emulsions.Finally,the catalyst was integrated into NaCas to construct a pH responsive interfacial catalytic system integrated with recyclable and reusable catalyst,and its cyclic catalytic performance could maintain at least 10 reaction cycles.(2)Construction of protein-based pH responsive Pickering emulsion for cascade reactionBased on understanding of the mechanism of NaCas regulating the stability/instability of the emulsion,a pH responsive Pickering emulsion was developed by ZCPOPs.Moreover,we explored a cascade PIC reaction by combining artificial enzymes and natural enzymes.The results show that the pH emulsion is almost suitable for all the oil phases that we know well,and has excellent versatility.In addition,the Pickering emulsion has dual properties of recovering catalyst and separating product,and has obtained high yield at least eight reaction cycles(more than 99%).Finally,using the constructed peroxidase like artificial enzyme combined with natural enzyme,we successfully developed a chemical and biocatalytic cascade PIC with both catalyst recovery and product separation,and realized the one pot cascade production of methylphenyl sulfoxide.(3)Application of protein-based CO₂/N₂ responsive emulsion to enzyme catalysisNext,we used NaCas to build CO₂/N₂ responsive emulsion to solve the influence of pH as a trigger on the enzyme.Then we explored the broad spectrum and specificity of the system,and reveal the regulation effect of NaCas on the stability of the emulsion at the interface.Finally,we verify the superiority of the system in the catalysis of enzyme.The results show that the system can not only effectively cycle more than 20 times,but also keep its response characteristics in high salt solution.In addition,the NaCas responsive emulsion can successfully transfer enzymes to the emulsion interface and form a CO₂/N₂ responsive emulsion with special enzyme interface mosaic structure.The enzyme adsorbed at the emulsion interface maximizes the range of liquid-catalyst-liquid interface region and promotes the mass transfer between the two phases,enabling the enzyme to be efficiently circulatory for more than 30 times of efficient bio-catalysis.The conversion rate was more than 90%.(4)Protein modified porous particles to construct core-shell structure for cascade PICThen,the multi-functional putamen structure was constructed by using the above NaCas physically adsorbed porous particles and used in the preparation of CO₂/N₂ responsive emulsion.The universality and broad-spectrum of the system were verified,and the emulsion structure and particle interface adsorption behavior were explored.Finally,the cascade PIC was explored using the putamen structure which loaded metal mimetic enzymes and natural enzymes for production of methylphenyl sulfoxide,and the catalytic efficiency and cyclicity of the catalyst were tested.The results show that the strategy has a good broad spectrum,that is,it is suitable for a variety of porous particles,such as MOF and SBA-15.Based on this structure,a cascade PIC with both catalyst recovery and product separation was successfully developed,which solved the problem of distance effect in the existing catalytic process,realized the one pot cascade production of methylphenyl sulfoxide with a conversion rate of 96%,and obtained high yield in three cycles.(5)Pickering based ultra-sensitive detection method for multiple recyclingA new practical SERS with fast cycle detection and wide applicability has been constructed based on the above-mentioned reaction emulsion system,combined with SERS structural unit and Photocatalyst(TiO₂ and zirconia).The stability,accuracy and cyclicity of the system have been verified,and its multi-purpose test in multiphase and gas detection has been explored.The results showed that the Pickering based SERS method was successfully constructed.In addition,the system also realizes the multi-purpose testing of liquid molecules and gas molecules.As a practical verification,we have realized the trace detection of waste oil,expired oil and juice containing illegal additives,and the detection limit is not higher than the conventional HPLC technology.Therefore,this study provides a simple,rapid and ultrasensitive analysis method for the identification of waste oil.Finally,the enhancement unit and extractant can be reused for many times by photocatalytic degradation of the residue.In summary,the intelligent response Pickering emulsion built around protein in this paper not only provides a new technical solution for the production of high value-added food and drug ingredients,but also provides a new,nondestructive and ultrasensitive detection means for food safety monitoring.It has a high degree of innovation and importance.