Structural Isolation Of Collagen-based Materials From Industrial By-products

Leather industry has been considered as a high resources consumption industry.A large amount of collagen-based by-product could generate during the processing,which is a biomaterial resource.This collagen-based wastes could pollute the environment,also cause a great waste of resources without efficient treatment.Bovine tendon as a by-product in food industry contains abundant collagen.Beside the food purpose,the development for its processing and utilization is of great significance.Based on the hierarchical structure of collagen,the processing methods of collagen from leather and food industry were discussed in this dissertation.Exploring the dissolution conditions and dissolution mechanism of skin collagen fibers and the dissociation conditions and mechanism of bovine tendon collagen,in order to provide scientific theoretical basis for the high-value utilization of biomass resources.Collagen fibers from tannery solid wastes were treated with aqueous solutions of inorganic salts and discussed the dissolution of inorganic salt to skin collagen fibers and its dissolution mechanism.Through solubility,SDS-PAGE,reduced viscosity of collagen solution,amino acid content,optical microscope and other tests,in order to discuss the cations and anions of inorganic salt to the effect of dissolving skin collagen fibers.According to all the results,the dissolution abilities of inorganicviscosity of collagen solution,the molecular weight tests,the proper dissolution solution was Na Br aqueous solution,the best condition was contacting time of 4h and temperature of 60?,and the Na Br aqueous solution concentration of 1mol/L,The lyophilized collagen obtained by dissolving the collagen fibers in Na Br solution still had the structural characteristics of collagen and the ability to form fibers.This part of the work provided a new way for the processing of collagen waste in the tannery industry.Skin collagen fibers were dissolved in Na Br solution to obtain collagen solution.The rheological behaviors of skin collagen solution were studied by rheological method.The steady-state shear rheological tests showed that the solution exhibited the characteristic of the dilute solution behavior at the concentration of 0.064wt%to1.92wt%.The solution showed pseudoplastic fluid at the range of 2.56wt%to4.48wt%,and the degree of pseudoplastic behavior became obvious with increasing the concentration of the collagen solution.The dynamic strain sweep results showed that G'of the collagen solution decreased with increasing?,while the change of G"was still in the plateau region,indicating that the G'was sensitive to?.G"was less than G'at the concentration of 0.64wt%,1.28wt%,3.20wt%,4.48wt%collagen solution,revealing that the behavior of collagen solution was elastic.When?was less than 100%,G'of collagen solution was stable,it was a linear viscoelastic region.When?was more than 100%,G'decreased rapidly with the increasing of?,and it was a non-linear viscoelastic region.The range of the linear viscoelastic region varied with the concentration of collagen solution.The dynamic frequency sweep results showed that G'and G"increased with the increasing of?.G'varied obvious in the low frequency region.In the high frequency region,the change of G'was not obvious.When the?was 100 rad/s,the G?can reach 10~2 Pa,while the value of G"was 10~0 Pa,that was G"<G'.The dynamic temperature sweep results showed that G?of the 4.48wt%collagen solution did not change significantly with increasing the temperature,indicating that G?was less sensitive to temperature.Tan?decreasesd with increasing the temperature in one?due to reduced frictional resistance of the segment.This work provided theoretical basis for the collagen processing and the rheological behaviors of the collagen solution.Collagen micro-and nano-fibers were successfully fabricated by the dissociation in the alkali/urea aqueous solutionby the frozening-thawing treatment and ultrasonic treatment.XRD results showed that the micro-and nano-fibers processed typical character of Type I collagen.The polarizing microscope was applied to observe the influences of agent components on collagen dissociation.It was found that the alkali solution played a major role in the swelling process of the tendon,and urea as the hydrogen bond breaker in dissociation processing.With increasing the freeze-thaw cycles,the swelling structure became more obvious and the crystalline regain gradually disappeared.SEM results showed that the microfibers had the typical light and dark periodic stripe of collagen,indicating that the micro-nanofibers retained the aggregated structure of collagen.Collgen nanofibers were obtained by further ultrasonic treament.With the increasing of ultrasonic energy,the aspect ratio and diamater of the fibers gradually decreased.Therefore,through freezing-thawing method,collagen microfibers with a relatively large aspect ratio(40.28-74.25)could be obtained.Nanofibers with a relatively low aspect ratio(17.31-36.54)could be obtained by ultrasonic treatment.Considering the hierarchical structure of bovine tendon,this work provided a new pathway for processing collagen from food industry.