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A Healthy Prebiotic Sugar from Seaweed

Prebiotics are indigestible food fibers and natural sugars that stimulate the growth of healthy bacteria in the gut. Xylooligosaccharides (XOS) are sugar fibers naturally found in the xylan fraction in plant fiber and they are made up of D-xylose oligomers. Due to its highly bonded structure and composition, XOS are stable at low pH and resistant to high temperature. Since humans don’t possess enzymes that breakdown XOS, they are unable to be digested and pass through the gastrointestinal tract. The prebiotic nature of XOS was recently discovered and evidence suggests XOS will improve gut microbiota, especially bifidobacteria. When healthy microbiota such as bifidobacteria increase in the gut, the growth of harmful microbiota, is inhibited while maintaining a healthy GI tract. XOS are also used in the food industry as a additive. Due to these health and food industry benefits, many researchers have attempted to develop simple procedures to extract XOS from natural sources, such as plant husks and shells.

A recent paper by Yamamoto et al. (2019) published in Process Biochemistry outlines attempts to develop a simple enzymatic procedure to extract XOS from red algae (commonly known as seaweed dulse). Red algae was selected due to its simple bio-architectural features. The harvested frozen dulse was lyophilized and subjected to organic extraction to separate the protein fraction from the carbohydrate-rich fractions [referred to as dulse xylan-rich fraction (DXRF)]. To evaluate a potential production method, DXRF was enzymatically digested with two types of commercial enzymes and products were analyzed by HPLC to identify XOS and other sugar molecules. To quantify the amount of galactose present in the hydrolyzed DXRF, Arbor Assays Galactose Colorimetric Detection Kit, K042-H1 was used. The effects of enzyme dose and reaction incubation time were altered to optimize the efficacy of enzymatic production of XOS from DXRF. The molecular masses of XOS were analyzed by Matrix-Assisted Laser Desorption/ Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF).

Results from sugar composition analysis confirmed that DXRF contained a higher percentage of xylose and lower percentages of glucose and galactose. This confirmed extracted dulse as a good source of XOS. Based on optimized parameters including commercial enzymes, dosing and incubation, approximately 66.6% of XOS were extracted from DXRF dulse materials. MADLI-TOF analysis confirmed the accurate structure of XOS in the DXRF products. Overall, the study established both the use of red algae seaweed dulse as a natural source for prebiotics and an enzymatic method for large scale XOS production from this feedstock.

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