Reducing Antigenicity Of Bovine Whey Proteins Using Kluyveromyces Marxianus Fermentation Combined With Ultrasound

Bovine whey protein is an important source of food for infants and young children,but it can easily cause allergic reactions and threaten their health.In this paper,the effect of ultrasonic treatment on the structure and function of whey proteins was studied,and the ultrasonic treatment conditions that were beneficial to fermentation and enzymolysis were screened.Kluyveromyces marxianus Z17,which can ferment and hydrolyze whey proteins,was selected from multiple food-borne strains.The fermentation conditions for Kluyveromyces marxianus Z17 reducing the antigenicity of whey proteins were optimized,and the optimal ultrasonic-enzymolysis conditions for the conversion of whey proteins by the intracellular crude enzyme of Kluyveromyces marxianus Z17 were explored.By examining the structure and function of whey proteins after ultrasonic treatment,we found that ultrasound can change the structure and function of whey proteins.After 20 min of ultrasonic treatment,unordered curl of ?-LA was increased by 11.3%,and unordered curl of ?-LG was increased by 14.0%.Ultrasonic treatment redshifted the maximum fluorescence emission wavelength of ?-LA and ?-LG up to 6 nm,while reducing the fluorescence intensity.In addition,ultrasound also changed the viscoelasticity of whey proteins emulsion,the microstructure and water holding capacity of whey proteins emulsion gel.The whey proteins pretreated by ultrasound were hydrolyzed by papain to a greater extent.Among 30 food-borne strains,Kluyveromyces marxianus Z17 has the strongest ability to hydrolyze whey proteins.The screened ultrasonic pretreatment conditions that make whey proteins most conducive to hydrolysis were: ultrasonic intermittent ratio 2 s: 1 s,ultrasonic power 200 W / m L,and ultrasonic time 10 min.The response surface methodology(RSM)was used to optimize the fermentation process conditions to reduce the antigenicity of whey proteins,and the extreme point was obtained:fermentation temperature 35 ?,initial pH 7.25,and inoculation volume 10%(v/v),the maximum reduction rates of ?-LA antigenicity and ?-LG antigenicity were 24.48% and52.86%,respectively.We separated the intracellular and extracellular crude enzymes of Kluyveromyces marxianus Z17 from the fermentation broth at the 30 th hour of fermentation,measured the activity of protease and peptidase,respectively.It was found that the intracellular crude enzyme had the activity of hydrolyzing protein,carboxypeptide and aminopeptide,while crude extracellular enzymes did not.Through the response surface methodology,the best ultrasound-enzymolysis conditions for reducing the antigenicity of ?-LA and ?-LG were obtained,the ultrasonic intermittent time 16 s(working time 5s),the ultrasonic power 400 W/m L,the initial pH 6.16,and the enzymolysis temperature 18.48 ?,which could reduce the antigenicity of ?-LA and ?-LG by 65.56%and 57.96%,respectively.