巴西洋菇水溶性多醣之特徵

Abstract

為瞭解巴西洋菇熱水可溶多醣的特徵，本論文使用三種酵素水解系統定量分析子實體萃取物中之(1,4;1,6)-α-D-glucans、(1,6)-β-D-glucans與(1,3)-β-D-glucans的含量，並配合分子篩層析分析與染劑呈色等方法了解各glucans之分子量分布，並比較液態菌絲培養所獲得之多醣性質之差異。巴西洋菇乾燥子實體含有9.1%之可溶性膳食纖維，有26.4%高量之nitrogen free extract。熱水萃取可將乾燥菇體中66.8%物質萃出，含有18.7%之可溶性粗多醣，其單醣組成含有94%之葡萄糖、6%之半乳糖及少量甘露糖和fucose；粗多醣具有40%之(1,4;1,6)-α-D-glucans、28%之(1,6)-b-D-glucans及2.2%之(1,3)-b-D-glucans和其他含有半乳糖、甘露糖和fucose的多醣，(1,4;1,6)-α-D-glucans之分子量介於177 ~ 1000 kDa，與碘溶液不會產生藍色或紫色之錯合，推測應為高分支度之(1,4;1,6)-α-D-glucans組成。(1,6)-b-D-glucans為直鏈型分子可被(1,6)-β-D-glucanase水解成gentiobiose及gentiotriose等三醣以上的寡醣，此多醣分子量介於6 ~ 800 kDa；而少量的 (1, 3 )-b-D- glucans 可能為具有短鏈分支之直線型分子，其分支度為0.15。另外，比較液態菌絲培養之樣品，發現液態培養之多醣組成和子實體多醣組成有顯著差異，其單醣組成半乳糖和甘露糖之比例佔85%以上，及少量之葡萄糖、阿拉伯糖和菇類特徵性糖fucose。若2%添加黑豆作為培養基質會顯著增加多醣總量，但由於黑豆基質之干擾，使菌絲多醣生成量之分析變為困難，但發酵過程中巴西洋菇會含fucose之特徵多醣，且含量隨培養天數增加而增加，可作為巴西洋菇液態多醣生成量之指標。

Abstract To investigate composition and structural characteristics of water-soluble polysaccharides of Agaricus blazei Murill, three enzymatic systems were applied to quantity the contents of (1,4; 1,6)-a-D-glucans, (1,6)-b-D-glucans and (1,3 )-b-D-glucans in the hot-water extracts of fruiting bodies. Molecular size distribution of these three D-glucans was revealed by size-exclusion chromatography and dye staining techniques. Polysaccharides from mycelium of this mushroom obtained from liquid culture were also studied for comparison. The dried fruiting bodies contained 9.1% of soluble dietary fibers (SDF) and had 26.4% nitrogen free extract. The yields of hot-water extracts and of crude polysaccharides were 66.8% and 18.7% of the solid, respectively. The crude polysaccharides contained 94% of glucose and 6% galactose with trace amount of fucose and mannose. The crude polysaccharides consisted of 40% of (1,4; 1,6)-a-D-glucans, 28% of (1,6)-b-D-glucans and 2.2% of (1,3 )-b-D-glucans and other polysaccharides containing galactose, fucose and mannose. The (1,4; 1,6)-a- D-glucans had molecular weight distribution in the range of 177~1,000 kDa and did not react with iodine solution to form blue or purple color. We proposed that the a-D-glucans had a branch-on-branch structure with high branching ratio. The (1,6)- -b-D-glucans were found to be linear molecules which could convert to gentiobiose, gentiotriose and small amount of gento-oligosaccharides using (1, 6)-b-D-glucanase and molecular weight distribution in the range of 6 ~ 800 kDa. The small amount of (1, 3 )-b-D- glucans were essential linear molecules with short glucosyl branches. The degree of branching was found to be 0.15. The polysaccharides obtained from mycelium culture contained high proportion of galactose and mannose consisting of about 85% of sugar components with appreciable amount of fucose and glucose and arabinose and were significantly different from polysaccharides from fruiting bodies. Adding 2% of blackbean (Glycine max) as medium significantly increased total polysaccharides yield of products. The inference of blackbean polysaccharides in the culture broth caused the difficulty of monitoring on the production of A. blazei polysaccharides. The fucose content in polysaccharide could serve a good index which increased as cultivating time increasing.