High-level TNF-alpha secretion and macrophage activity with soluble beta-glucans from Saccharomyces cerevisiae.

We have previously reported that water-soluble beta-glucan completely devoid of mannoprotein and purified from the yeast cell wall effectively stimulated the macrophage function (Biosci. Biotechnol., Biochem., 65, 4, 837-841 (2001)). In this present study, to increase the yield of water-soluble beta-glucan, the wild type of Sacharomyces cerevisiae, JH, was treated with a combination of UV irradiation and laminarinase (endo-beta-(1,3)-glucanase) to yield the laminarinase-resistant mutants, JUL1 and JUL3. Water-soluble beta-glucans that were free of mannoprotein from JH, JUL1 and JUL3 were purified and their effects on TNF-alpha secretion and phagocytosis by macrophages were evaluated. Crude beta-glucan was first solubilized from the yeast cell wall by alkaline extraction and then subjected to an acid treatment. The residual mannoprotein was completely removed by DEAE and ConA chromatography. The yield of water-soluble beta-glucan in both mutants (JUL1, 5.11%; JUL3, 5.76%) was about 5-fold higher than that of the wild type (1.16%). The water-soluble beta-glucan from JH induced TNF-alpha secretion slightly more than that from JUL1 or JUL3: TNF-alpha secretion by JH at 50, 200, 500 microg/ml of beta-glucan was 11-17% more than that by JUL1 or JUL3 for the same treatment. Beta-glucan from the wild type stimulated phagocytosis slightly more than that from the mutants. These mutants could therefore effectively produce purified water-soluble beta-glucan with immune activity.