Preparation,Physicochemical Properties And Biological Activities Of Dietary Fiber And Polysaccharides From Laminaria Japonica

Laminaria Japonica is rich in a variety of active ingredients,such as Laminaria Japonica polysaccharide（LJP）and dietary fiber（DF）.Laminaria Japonica DF is a carbohydrate polymer that cannot be absorbed and digested by the human body,and Laminaria Japonica polysaccharide（LJP）is a sulfated polysaccharide with various biological activities.However,due to the large molecular weight（Mw）and complex structure of Laminaria Japonica DF and LJP,their absorption and utilization by the body are limited.Therefore,it is necessary to adopt the superfine grinding method and ultrasonic degradation method,which can not only maintain the biological activity of Laminaria Japonica DF and LJP,but also reduce Mw,and then verify by measuring different properties.The results of the study are as follows:（1）The superfine grinding method is a physical method that pulverizes DF with high efficiency and effectively maintains its activity.The DF which extracted by chemical method combined with enzymatic method is ultra-finely pulverized to obtain ultra-fine pulverized DF,the particle size is obviously smaller,and the Laminaria Japonica TDF is reduced by 63.46%;the content of dietary fiber increases slightly,and is almost unchanged;The gel strength of Laminaria Japonica IDF decreased by 46.43%,and the viscosity increased by 48.17%,indicating that the particle size reduction of Laminaria Japonica DF has a significant impact on its rheological properties;the nitrite adsorption capacity of dietary fiber increased45.99%,compared with Laminaria Japonica IDF.Cation exchange capacity（CEC）enhanced 46.15%and Cholesterol adsorption capacity（CAC）improved 107.34%,The adsorption amount of ultrafinely pulverized IDF Pb²⁺reduced by 87.31%,the adsorption amount of ultrafine pulverized IDF Cu²⁺decreased by 54.74%,and the adsorption amount of ultrafine pulverized IDF Zn²⁺decreased by 97.89%,the adsorption capacity of Cu²⁺and Zn²⁺decreased.Compared with Laminaria Japonica SDF,the glucose absorption capacity of Laminaria Japonica ultra-finely pulverized SDF was increased by 27.90%;compared with Laminaria Japonica IDF,the glucose absorption capacity of Laminaria Japonica ultra-finely pulverized IDF was enhanced by 36.78%.Compared with Laminaria Japonica DF,ultra-finely pulverized DF showed higher glucose adsorption,which contributed to its efficient function in the intestine.（2）Ultrasonic degradation is an environmentally friendly physical method for degrading polysaccharides with high degradation rate without changing the primary structure.Ultrasonic Laminaria Japonica polysaccharide（ULJP）prepared by ultrasonic degradation has better biological activity and application value.Through single factor experiment,the optimal extraction conditions of LJP extract were determined as follows:extraction temperature was 70℃,extraction time was 2 h,solid-liquid ratio was 50,and number of times for extraction was 2 times.The extract was purified by three-phase separation method to obtain LJP;LJP was degraded by ultrasonic to obtain ULJP.The Mw of LJP and ULJP were determined to decrease by29.95%;by infrared spectroscopy,both LJP and ULJP contained sulfate groups,and their primary structures kept unchanged;ULJP is a loose fibrous packing;thermogravimetric analysis shows that the thermal stability of LJP is greater than that of ULJP,and the Mw and thermal stability are positively correlated.Hexopyranose,and is mainly linked by 1,4-glycosidic bonds.（3）By measuring the scavenging rates of DPPH and ABTS free radicals for ULJP and LJP,the scavenging rates of DPPH and ABTS radicals increased by16.01%and 14.03%,respectively,indicating that ULJP has better antioxidant activity than LJP;The inhibition rate of ULJP and LJP onα-amylase increased by 12.27%,showing that ULJP has better hypoglycemic activity than LJP;through in vitro RAW264.7 cell assay,NO inhibition assay and QPCR experiments,respectively,from the levels of inflammatory mediators and genes,It was verified that ULJP sugar has more excellent anti-inflammatory activity than LJP.In conclusion,superfine grinding can effectively pulverize Laminaria Japonica dietary fiber and improve the activity of Laminaria Japonica dietary fiber.Ultrasonic degradation can effectively degrade Laminaria Japonica polysaccharide and significantly improve the biological activity of Laminaria Japonica polysaccharide,which provides a theory for the in-depth utilization and research and development of Laminaria Japonica in medical,chemical engineerning and food industry.