The Extraction Process Of Carrageenan Suitable For Wet Spinning And The Study Of The Conformation Of Carrageenan In Dilute Solution

Carrageenan is a linear sulfate polysaccharide with excellent antiviral,antioxidant,gelatinous and biocompatible properties,which is widely used in food,pharmaceutical,cosmetic and other industrial fields.Carrageenan fiber has a broad application prospect in textile,household,medicine,and personal care because of its abundant raw material source,self-fire retardant and biodegradability.The traditional carrageenan extraction process matches its application in food and pharmaceuticals,and so far there is no carrageenan extraction process specifically for spinning applications.In this study,we proposed an environmentally friendly,high-yield carrageenan extraction process suitable for wet spinning:the non-alkali pretreated Hypnea cervicornis extract was directly converted into carrageenan spinning solution without drying,and then carrageenan fibers were prepared by the wet spinning process.The improved carrageenan extraction method(61.8±1.1%)showed higher yields compared to the conventional extraction method(36.0±1.3%),and infrared spectroscopy(FTIR)and nuclear magnetic resonance carbon spectroscopy(¹³C NMR)showed that the carrageenan extracted by the new process was mainly?-carrageenan,and the alkali pretreatment step did not significantly change its structure.The properties of carrageenan spinning solution and carrageenan fibers were characterized using dynamic light scattering(DLS),scanning electron microscopy(SEM),elemental content analysis(EDS)and tensile tests,which showed that the particle distribution of the carrageenan spinning solution prepared without alkali pretreatment was uniform and suitable for spinning,and the mechanical strength of carrageenan fibers prepared by the new extraction process(0.80±0.17 cN/dtex)was comparable to that of the carrageenan fiber prepared by the conventional extraction method(0.73±0.19 cN/dtex).The biological activity and processing properties of carrageenan are inextricably linked to the molecular weight and conformation of carrageenan.The?-and?-carrageenan were measured by triple detector coupled gel permeation chromatography(TDA-GPC)and the results showed that the molecular weights of?-and?-carrageenan were 685,800 Da and408,300 Da,respectively.The conformation of?-and?-carrageenan were obtained by analyzing the Mark-Houwink curves and hydrodynamic diameters of carrageenan molecules:at low molecular weights,the carrageenan molecular chains are more rigid and exhibit a rigid rod conformation;at medium molecular weights,the molecular chains become less rigid and exhibit a conformation between rigid rods and random coil;at large molecular weight,the molecular chain rigidity continues to decrease and the conformation is random linear.The effects of concentration and temperature on the molecular weight of carrageenan and the molecular conformation in dilute solutions of carrageenan were investigated by TDA-GPC tests.The results showed that the change of concentration had no significant effect on the molecular weight,hydrodynamic radius,mean square rotation radius and conformation of?-and?-carrageenan in solution;the increase of temperature decreased the molecular weight of?-carrageenan and the rigidity of molecular chains.The molecular conformations of both?-and?-carrageenan were semi-rigid macromolecules,and the molecular chain rigidity of?-carrageenan was greater than that of?-carrageenan.