Study On Modification And Surface Activity Of Protein Separation In Silk Reeling Wastewater

China is the world’s largest silk producer and exporter,and has a long history of planting mulberry and raising silkworms.Our country’s silk reeling enterprises are mainly concentrated in the main silk production areas,which generally have the characteristics of small production scale and scattered distribution.This leads to the fact that the reeling wastewater containing a large amount of organic matter cannot be fully utilized,resulting in serious waste of resources.Therefore,to increase the surface activity of reeling wastewater,this paper used the isoelectric point method to separate the proteins,hydrolyzed the protein isolated from the reeling wastewater by Alcalase,and graft-modified the hydrolysate with glucose.By changing the structure of the isolated protein to improve the surface activity.The innovation of this experiment was to use reeling wastewater separation protein as a raw material for modification treatment,and analyzed the changes in surface properties and structural changes.The solubility,foaming performance,emulsifying performance,free amino content and surface hydrophobicity were used to characterize the surface activity of the separated protein.The changes in protein structure were analyzed by fluorescence spectroscopy and circular dichroism chromatography.Through particle size distribution and Zeta potential changed,the electric charge system was analyzed.The results of the study on the changes in the medium charge were as follows:(1)The isoelectric point method was used to separate the protein in the reeling wastewater,and the protein in the reeling wastewater was obtained by centrifugation and freeze drying.Through single factor experiments and orthogonal experiments to sudy the effect of pH,reaction temperature,precipitation time,and stirring time on protein recovery.The experimental results showed that: when the pH was 4,the temperature was 35 ℃,the precipitation time was 2 h,and the stirring time was 15 min,the separated protein had the maximum recovery rate,the recovery rate reached 69.75%.(2)Firstly,through single-factor experiment and orthogonal experiments to establish the optimal hydrolysis conditions for Alcalase alkaline protease to hydrolyze the protein isolated from silk reeling wastewater.At the substrate concentration of 3%,the temperature of 60°C,and the pH = 8.0,under the condition of 0.16% enzyme addition,the hydrolysis efficiency of the separated protein was the highest.Under this condition,the protein separation of silk reeling wastewater was enzymatically hydrolyzed,and protein hydrolysates with different degrees of hydrolysis were prepared according to different reaction times.The experimental results showed that after the enzymatic hydrolysis treatment,the soluble protein content of the sample had increased significantly,the highest value was2.15 mg/m L,which was 58.37% higher than the original protein isolate.The foaming performance was significantly improved.When the degree of hydrolysis was 3.85%and 5.37%,the foamability and foaming stability were respectively maximized;the emulsification was maximized when the degree of hydrolysis was 3.85%,the most stable when the degree of hydrolysis was 4.35%;the content of free amino groups increased with the degree of hydrolysis after hydrolysis treatment.When the degree of hydrolysis was 4.35%,the maximum content of free amino groups was 4.5 mmol/L;The surface hydrophobicity decreased after hydrolysis treatment.The results of endogenous fluorescence spectroscopy showed that the maximum absorption peak of the sample after hydrolysis was red-shifted,the particle size became smaller,the absolute value of Zeta potential increased,the secondary structure changed,and the irregular curl content increased.The experimental results showed that Alcalase alkaline protease could significantly changed the structure and improved the surface activity of the isolated protein,but the degree of improvement was limited.(3)Glucose was used to modify the hydrolyzed protein in reeling wastewater,and the effect of sugar grafting on its surface activity and structure was studied.The size of the degree of grafting could be obtained by calculating the content of free amino groups.The experimental results showed that when the grafting degree was 60.04%,the soluble protein content of the graft was the largest;the foamability and foaming stability of the graft were the maximum when the grafting degree reached 41.93%;the emulsification and emulsification stability of the graft reached the maximum when the grafting degree was 36.45%,and the hydrophobicity results showed that the hydrophobicity decreased after modification by glucose grafting.The results of endogenous fluorescence spectroscopy showed that the fluorescence intensity of the graft was enhanced,and the results of exogenous fluorescence spectroscopy confirmed the fact that the hydrophobicity decreased.The particle size score showed that the average particle size increased,and all graft products showed new peaks.The absolute value of Zeta potential increased firstly and then decreased,and the absolute value of Zeta potential reached its maximum when the grafting degree was 54.71%.The results of circular dichroism chromatography showed that after sugar grafting occurred,the secondary structure of the composite product was destroyed,and the irregular curl structure increased but still accounted for the main part.The above results indicated that after the glucose grafting reaction,the molecular structure had changed,which resulted a new increase in the surface activity of the hydrolyzed protein isolate.