Methods for yeast β-glucan extraction
The methods discussed are based on the β-glucans obtained after the yeast cell is lyzed or disrupted and the cell cytoplasm is liberated. The yeast cell lysis is achieved with physical (sonication, homogenization) and chemical (alkali, acid) and/or enzymatic (lytic enzymes, glucanases) procedure. Cell disruption is achieved with enzymatic or chlorite oxidation procedures. The yeast cell lysis is very important for the biotechnological use of yeasts in the exploitation of their cellular components. For this reason, more and more techniques for yeast cell disruption are being investigated and have been developed.[17-20] In a subsequent step, the obtained yeast cell walls have to be purified. At the beginning, the mannoprotein and then the lipids and proteins are removed, leading to different fractions of purified β-glucan. Various available yeast β-glucan extraction and purification methods from different starting materials are reviewed in Fig. 1 as a schematic process for each method. The steps needed for each different β-glucan extraction method, are named and reviewed in Table 1. Also, the optimal conditions in each extraction step of each method are reviewed in Table 2.