<Doctor's Thesis>Study on Effects of Edible Algae and Algal Polysaccharides on Intestinal Microorganisms

Some brown algae, red algae and green algae have been consumed as marine foods in Japan from olden times. It is well known that algal polysacchalides (dietary fibers) have good effects on human health, such as the improvement of constipation, the supression of blood lipid level and the excretion of toxic compounds. On the other hand, the effects of algal polysaccharides on the intestinal microflora is not well known, though dietary fibers have been considered to affect health through the activity of intestinal microflora. This study was carried out to determine the effects of marine algae and algal polysaccharides on the intestinal microflora and intestinal environment. The outlines of the study are as follows. 1. Fermentation of Algal Polysaccharides by Intestinal Bacteria in vivo 1-1. Fermentation of Algal Polysaccharides by Human Intestinal Bacteria Dilutions of human feces were tested for their ability to ferment polysacchalides (alginate, laminaran, fucoidan, carrageenan, agar and cellulose). Alginate and lammaran, especially laminaran, were fermented by fecal microflora, although fucoidan, carrageenan and cellulose were not fermented. Bacteroides ovatus showed the ability to ferment alginate. B. ovatus and some Clostridium spp. fermented laminaran. 1-2. Fermentable Dietary Fiber in Dried Products of Brown Algae The content of fermentable dietary fibers, laminaran and alginate, in 22 dried products of brown algae were studied. After washing with methanol, 0.1 mol /l hydrochloride fractions (F1: crude laminaran and fucoidan), 1% sodium carbonate fractions (F2: crude alginate) and insoluble fractions (F3) were extracted from the algae using ethanol precipitation method. F1, F2 and F3 ranged from about one to 22%, 10 to 67% and three to 59%, respectively, of dry matter. Laminaran was detected in three products by bioassay using Clostridium ramosum. Laminaran content was the highest in arame Eicenia bicyclis. Fucoidan was not detected in arame by TLC. Fermentation pattern of F1 and F2 of arame by human fecal flora were similar to that of laminaran and alginate, respectively. 2. Dietary Effects of Edible Algae on Cecal Microflora and Levels of Blood Lipid in Rats To examine the dietary effects of nine edible algae (hijiki Hizikia fusiforme, kombu Laminaria sp. wakame Undaria pinatifida, mekabu (sporophyll of U. pinatifida), arame, mozuku (okinawa-mozuku Cladosiphon okamuranus), aosa (hitoegusa Monostroma nitidum), aonori Enteromorpha sp. and nori (amanori Porphyra sp.) on the intestinal microflora and the levels of blood lipid, the diets containing 1% and 5% of these algae were administered to male rats for one week. All of the diets containing algae increased the weight of feces. Most of these algae suppressed the level of serum triglycerides (TG) and free fatty acids (NEFA). The number of bifidobacteria increased with the diets containing 1 % algae, while several diets containing 5% algae suppressed some bacterial groups. 3. Effects of Algal Polysaccharides (Dietary Fibers) on Cecal Microflora and Levels of Blood Lipid in Rats 3-1. Effects of Algal Polysaccharides on Cecal Microflora and Levels of Blood Lipid in Rats To determine the effects of algal polysaccharides (laminaran, carrageenan, agar, high viscous alginate (HAG) and low viscous alginate (AG5)) at 2% level on the intestinal microflora and levels of blood lipid, these diets were administered to male rats for a week. Laminaran and carrageenan increased the cecal weight. Laminaran decreased the cecal pH value, while carrageenan and agar raised cecal pH value. No significant effects were shown in the case of HAG diet, while cecal pH value, serum TG, and serum cholesterol (TC) clearly dropped in the AG5 diet. Laminar an and AG5 had tendency to increase the ratio of bifidobacteria to total cecal microflora. On the other hand, carrageenan had tendency to decrease the ratio of bifidobacteria. Carrageenan increased the number of cecal enterobacteriaceae. Agar decreased the