Laboratory for Immunopharmacology of Microbial Products, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
Oriental Yeast Co., Ltd., Yeast Function Development Unit, 3-6-10, Azusawa, Itabashi, Tokyo, 174-8505, Japan.
Int J Biol Macromol. 2018 Feb;107(Pt B):2269-2278. doi: 10.1016/j.ijbiomac.2017.10.094. Epub 2017 Oct 16.
β-glucan is widely distributed in nature as water soluble and insoluble forms. Both forms of β-glucan are utilized in several fields, especially for functional foods. Yeast β-glucan is a medically important insoluble particle. Solubilization of yeast β-glucan may be valuable for improving functional foods and in medicinal industries. In the present study, we applied an acid degradation method to solubilize yeast β-glucan and found that β-glucan was effectively solubilized to low-molecular weight β-glucans by 45% sulfuric acid treatment at 20°C. The acid-degraded soluble yeast β-glucan (ad-sBBG) was further fractionated into a higher-molecular weight fraction (ad-sBBG-high) and a lower-molecular weight fraction (ad-sBBG-low). Since ad-sBBG-high contained mannan, while ad-sBBG-low contained it only scarcely, it was possible to prepare low-molecular weight soluble β-glucan with higher purity. In addition, ad-sBBG-low bound to dectin-1, which is an innate immunity receptor of β-glucan, and showed antagonistic activity against reactive oxygen production and cytokine synthesis by macrophages. Thus, this acid degradation method is an important procedure for generating immune-modulating, low-molecular weight, soluble yeast β-glucan.
β-葡聚糖广泛存在于自然界中，有可溶性和不可溶性两种形式。这两种形式的β-葡聚糖都被应用于多个领域，尤其是在功能性食品方面。酵母β-葡聚糖是一种具有重要医学意义的不可溶性颗粒。酵母β-葡聚糖的溶解化可能对改善功能性食品和医药工业具有重要价值。在本研究中，我们应用酸降解法来溶解酵母β-葡聚糖，发现 45%的硫酸在 20°C 下处理可以有效地将β-葡聚糖降解为低分子量β-葡聚糖。经酸降解得到的可溶性酵母β-葡聚糖（ad-sBBG）进一步被分为高分子量部分（ad-sBBG-high）和低分子量部分（ad-sBBG-low）。由于 ad-sBBG-high 含有甘露聚糖，而 ad-sBBG-low 几乎不含甘露聚糖，因此可以制备出具有更高纯度的低分子量可溶性β-葡聚糖。此外，ad-sBBG-low 与 dectin-1 结合，后者是β-葡聚糖的固有免疫受体，并且对巨噬细胞中活性氧的产生和细胞因子的合成具有拮抗作用。因此，这种酸降解方法是生成具有免疫调节功能、低分子量、可溶性酵母β-葡聚糖的重要步骤。
