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    Search for health functional ingredients in red algae, a low-use resource; a method for preparing new oligosaccharides

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    Search for health functional ingredients in red algae, a low-use resource; a method for preparing new oligosaccharides × SDGs

    • SDGs  SDGs12  

         We found that the low-use red alga Dulse from Hokkaido, Japan is rich in a polysaccharide called xylan, which has a different structure from that of xylan from land plants. In addition, we found that xylooligosaccharides specific to Dulse, prepared by enzymatic degradation of Dulse xylan, showed selective growth-promoting effects on bifidobacteria. Through these studies, we would like to contribute to the development of functional food ingredients that improve people's health.


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    Outline

       

    • Dulse is a red algae that grows on the kombu culture rope, a special product of Hakodate City, and many are discarded. On the other hand, it is known to have a polysaccharide with an unusual structure. Here, an oligosaccharide having an unusual structure was prepared from a polysaccharide of Dulse and the structure was determined. In the future, we will look for its health functionality.

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    Characteristics of Red Alga "Dulse"


    • Red Alga “Dulse”

      Dulse is a red algae that grows in cold waters. Dulse can be eaten

      overseas, but most of it was unused in Japan. In particular, it was

      difficult to dispose of a large amount of dulse because it grew on

      the culture rope for kelp, a special product of Hakodate.






      Nutrients in Dulse

      Dulse, like other red algae such as laver (“Nori” in Japanese), contains a lot of protein and the amount is comparable to soybean. On the other hand, it contains a lot of carbohydrates, especially dietary fiber. 

      Dulse’s cell walls contain polysaccharides classified as dietary fibers called xylan.

      This xylan has an unusual structure that is different from that of land plants.


    • Dietary fiber 頁面
    • Xylan 頁面
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    Functionality of xylooligosaccharides with different structures


    • [Open Access] Maeda et al., 2012, Bioscience, Biotechnology, and Biochemistry 網址
    • Structure of Hexagon 頁面

    • Xylan (Polysaccharides)

      The polysaccharide “xylan” is a plant cell wall-forming polysaccharide that is the most common after cellulose.

      The backbone of many xylan in land plants has a structure in which xylose is β-(1→4) bonded. The Oligosaccharides

      obtained by enzymatic degradation of this xylan have a prebiotic effect. On the other hand, the oligosaccharides

       obtained from β-(1→3)-xylan, possessed by some green algae, have cancer cell apoptosis-inducing action.


      Xylan in Dulse

      As shown in the figure, Dulse's xylan has both β-(1→3) and β-(1→4) bonds in the backbone. The oligosaccharide

      obtained from it has a structure different from that of conventional xylooligosaccharides. And it is considered to

      have a unique health function.


      Purpose of Research

      In this study, we explore the health function of xylooligosaccharides from dulse for effective utilization of marine

      waste. Therefore, this xylooligosaccharide was prepared here. In addition, the structure of this xylooligosaccharide

      was determined.

    • Oligosaccharide 頁面
    • β-(1→4)-xylan 頁面
    • Prebiotics 頁面
    • Apoptosis 頁面
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    Extraction of xylan from dulse, preparation of oligosaccharide and structural analysis


    • Extraction of Xylan and Preparation of Xylooligosaccharide

      First, samples for analysis was prepared. In other words, dulse, exterminated in Hakodate city, was freeze-dried,

      crushed and removed lipids and proteins. The obtained cotton-shaped xylan was hydrolyzed by a commercially

      available carbohydrate hydrolase.


      Analysis of Xylooligosaccharides

      The xylan hydrolyzate was analyzed in detail using various instruments. The composition of the product in the hydro-

      lyzate was analyzed by HPLC, the molecular weight was analyzed by GC-MS, and the structure was analyzed by NMR.

      These analyzes confirmed whether xylooligosaccharides with a structure peculiar to dulse were generated.

    • HPLC 頁面
    • NMR 頁面
    • GC-MS 頁面
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    Structure of oligosaccharide from dulse xylan


    • Result of Analyzing Xylan Hydrolyzate

      An unidentified peak was detected in the enzymatic degradation product from dulse xylan by HPLC analysis.The

      material of this peak was analyzed by GC-MS and NMR. As a result, we found that it is β-(1→3)/β-(1→4)-xylo-

      triose, which is characteristic of the structure of dulse xylan.

    • Yamamoto et al., 2019, Process Biochemistry 網址
    • Reducing end 頁面
    • Xylotriose 頁面
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    Future plans

      • Simple extraction method of dulse xylan without using organic solvent


      • Efficient preparation of dulse xylooligosaccharide


      • Functional evaluation for intentional flora

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