A new isolation method of β-d-glucans from spent yeast Saccharomyces cerevisiae

β-d-glucans, which are widely distributed in the cell walls of microorganisms, mushrooms and plants, have received much attention with respect to their biological functions. Traditional method for preparing β-d-glucans from Saccharomyces cerevisiae cells was based on repeated extractions with acid or alkali solutions, which resulted in degradation of the β-d-glucan chains. A new mild method to extract β-d-glucans from S. cerevisiae cells was proposed in this paper, which was composed of induced autolysis, water and organic solvent treatment, homogenization and protease hydrolysis. Compared with traditional isolation methods, this new method had distinct advantages that it gave high yields and purity of β-d-glucans and kept β-d-glucans native conformation. Furthermore, this isolation procedure did not pollute the environment and could be easily scaled-up to an industrial process. The experimental data indicated that each extraction step had its significant effect on β-d-glucans preparation, especially, the induced autolysis and homogenization. After 24 h of induced autolysis, 48% (w/w) cellular substances were released, whereas the cell wall nearly remained intact. Treated by hot water, the mechanical strength of the yeast cell wall decreased with the removal of the mannoproteins, which caused the yeast cell walls easy to be disrupted. As a result, the ratio of broken yeast cell slightly exceeded 95% after three passes in homogenization treatment in 70 MPa. Finally, β-d-glucans were obtained at a yield of 91% of the original ratio in the yeast cell walls and with a purity of up to 93% (w/w).