Study On The Performance Of Pickering Emulsion Dispersed By Chaperonin Nano-barrels And Its Application

Stabilization of Pickering emulsions via particles of biological origin exhibits a great potential to be widely applied in food,cosmetic or biomedicine formulation,due to their excellent biocompatibility,biodegradability as well as functional properties.Among them,proteins nanoparticles are particularly interesting,whose naturally amphiphilic nature and nutritional value impart a dual benefit in the preparation of high-grade Pickering emulsions.While most commonly available protein nanoparticles display superior mono-dispersity in aqueous solutions,they are much vulnerable to the process variables of industrial emulsions(e.g.,high temperatures or broad p H shift).Moreover,the surface of a protein usually presents a highly heterogeneous distribution of charge and hydrophobicity,leading to unpredictable protein orientation at interfaces and compromised surface activity.Surface modification or even intended denaturation is frequently performed to further improve protein's packing around dispersed phase droplets and thus its emulsive-ability,which,however,is uncontrollable to a large extent and adds an extra layer of complexity to formulating protein-supported emulsions.Consequently,it is highly desirable to develop inherently robust protein nanoparticles with finetuned architecture and high surface activity to efficiently stabilize high-grade Pickering emulsions.In this paper,the chaperone GroEL nano-barrels protein and its single-ring mutant SR were introduced as new Pickering emulsifiers.On the one hand they have good thermal and chemical stability,on the other hand their top hydrophobic chamber contributes to the effective dispersion of the oil phase.This paper mainly studies the composition and stability of GroEL and SR-stabilized Pickering emulsion,and explores the potential applications in formulating functional foods.It mainly includes the following aspects:First,the target proteins GroEL and SR were expressed and purified.The molecular weight,structural integrity,morphology and monodispersity of the target protein were characterized by SDS-PAGE,mass spectrometry,transmission electron microscopy and dynamic light scattering.In addition,the green fluorescent dye Alexa Fluor 488(AF488)was used to fluorescently label GroEL and SR,which laid the foundation for Pickering emulsion research.Secondly,the Pickering emulsion was prepared using the chaperone GroEL as an emulsifier.The microstructure of the Pickering emulsion was characterized by optical microscopy and fluorescence microscopy,and the formulation was systematically optimized.The results show that the oil-water ratio is 0.05-0.35(v/v),and the protein content is between0.05-0.45(wt.%).The emulsion stability is good,and the droplet size is about 200-450 nm.The Zeta potential study of Pickering emulsion shows that the surface charge of GroEL plays an important role.At the same time,the Pickering emulsion exhibited good stability at neutral to alkaline p H,ionic strength up to 200 m M,and storage temperature to 65 °C.Hydrodynamic studies have shown that the emulsion is non-Newtonian fluid,and when the oil-water ratio exceeds 0.30(v/v),an advanced gel network structure is formed.The entrapment and stability studies of ?-carotene showed that the effects of oxidizing agents,ultraviolet radiation,reducing agents and sucrose on the stability of ?-carotene encapsulated in GroEL-stabilized Pickering emulsions were successively reduced.In addition,temperature,ionic strength,p H,and the like have an effect on the stability of the encapsulated ?-carotene by affecting emulsion stability.Finally,the stability properties of GroEL's single-ring mutant SR on Pickering emulsion were compared.Studies have shown that the stability and suitable stability conditions of SR for Pickering emulsion are almost the same as those of GroEL.However,SR-stabilized emulsion ionic strength tolerance is stronger than GroEL,while GroEL-stabilized emulsion has stronger temperature tolerance than SR.Studies on the embedding and stabilization of ?-carotene showed that the effects of GroEL and SR were basically the same.