Method 2
This method[22] is applied on spent brewer's yeast Saccharomyces cerevisiae cells from which the β-glucan content is isolated. This method is also oriented to the use of brewery wastes for the production of β-glucans from spent yeast by-product remaining after alcoholic fermentation for beer production. The method is based on yeast self-lysis by cell autolysis procedure. This type of lysis is mild instead of the use of chemicals or mechanical disruptors (homogenizers, sonicators). The β-glucan is extracted in one step process with the use of NaOH. Yeast cells are first sieved (125 µm analytical sieve) and then filtrated in vacuum. The yeast cells are debittered with the use of NaOH (pH 10 / 50°C / 10 min), centrifuged (6000 rpm/10 min) and washed three times with distilled water. Then, the debittered cells are autolyzed (50°C / 36 h) and the yeast extract (supernatant) is separated from raw yeast cell material (sediment) by centrifugation (6000 rpm / 4°C / 10 min). The yeast cells, after washed three times with distilled water, are then treated with NaOH (1 M / 90°C / 2 h). The conditions for yeast cell autolysis and NaOH extraction are optimized. The insoluble β-glucan is received as a sediment after centrifugation (6000 rpm / 4°C / 10 min) where the supernatant is discarded. The β-glucan is washed three times with distilled water and then subjected to drying. The yield is 13.64% and calculated as the percent difference between the dry weight of produced β-glucans and the dry weight of the starting spent brewer's yeast.[22] Insoluble wet β-glucan suspension (1.5% w/v) can be transformed to microparticles with further sonication for 15 min for avoidance of the aggregation of β-glucan particles.