Search for health functional ingredients in red algae, a low-use resource; a method for preparing new oligosaccharides × SDGs
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.
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.
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.
Functionality of xylooligosaccharides with different structures
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
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.