Study On Mass Transfer And Reaction Characteristics Of Protease In Goatskin

The tanning,an ancient and traditional industry,plays an important role in the highquality utilization of agricultural and sideline products and the conversion of high valueadded products during the industry chain of animal husbandry,agriculture,industry and other industries.However,a large amount usage of chemical materials in the tanning process is likely to cause serious environmental pollution.Thus the use of enzyme preparations is a new direction for the clean production of the tanning industry.The enzyme has attracted much attention in the preliminary steps of leather production,including soaking,unhairing,degreasing and especially bating due to its merits of high efficiency and eco-friendliness.The enzymatic reaction in leather processing is a mass transfer controlled process.Therefore,it is of great significance to study the enzyme mass transfer mechanism in skin matrix in order to use and control the enzymes for leather production.In this thesis,the bovine serum albumin and several proteases were labeled with fluorescein isothiocyanate.And devices were designed to analyze the static one-way and turbulent mass transfer processes of enzymes or proteins in skin matrix under laboratory conditions.The method of quantitative detection of enzyme in skin matrix was established by combing the devices with fluorescence detection in slices.Enzyme oneway and turbulent mass transfer process in skin matrix were studied.The results showed that enzyme concentration was regularly declined along the mass transfer direction.Based on the Fick's law,and combing the theories of Mass Transfer Equilibrium,Ideal "Plate" and Exponential Decline with the actual enzymatic mass transfer process in tanning,the kinetic equation model of enzyme mass transfer was derived.After modification,the kinetic equation suitable for the simulation of the mass transfer process of the enzyme in skin matrix was obtained.The results of data fitting and prediction analysis showed that the derived equation was competent to fit the actual mass transfer data of the enzyme in skin matrix.The mass transfer curve predicted through the parameter changes accorded with the actual mass transfer trend,showing the applicability and theoretical guiding significance of the higher dynamic equation.The effect of penetration time,the concentration or type of enzymes,and their interaction on the mass transfer process were analyzed by the kinetic equation.The obtained results showed that the enzyme concentration in skin matrix increased linearly with time.The rate of enzyme mass transfer was the fastest when the concentration was 100 U/mL on the condition of static one-way penetration.However the mass transfer rate was the fastest on the condition of turbulent mass transfer when the concentration is 50 U/mL.The difference of the mass transfer rate was more obvious when transferring in the back part of the skin,and less obvious in the initial stage(< 5 min)of a mass transfer process.The effect of enzyme concentration on the mass transfer rate increased with the time.The proteins with smaller molecular weight are more easily transported through the interfiber space of the skin,but the effect of molecular weight on mass transfer rate is less than that of the mechanical force(turbulent condition).The transfer coefficient in kinetic equation is closely related to the structure of the skin matrix.As the mass transfer and the reaction process progress,the parameters in the equation changed regularly.The parameters of the kinetic equation changed with time during the process of mass transfer and reaction.This was consistent with the total protein dissolution in the reaction process,showing the close relationship between the mass transfer process of the enzyme and the process of the reaction.The study of the mass transfer of protease in skin matrix and its reaction characteristics are of great significance for the clean production of tannery.