# \(\beta\)-Glucans from Yeast--Immunomodulators from Novel Waste Resources
## 9 Extraction and Characterisation of \(\beta\)-Glucans  
The yeast cell wall's rigidity avoids external tension, and \(\beta\)-glucans are cell wall components so it is difficult to extract them. A single extraction technique is not always adequate to remove \(\beta\)-glucans from yeast. Because of this, a variety of procedures are frequently employed to extract \(\beta\)-glucans, including heat treatment, ultrasound, and enzymes [124]. The extraction method must not affect the molecule's structure as this is correlated to activity. Aggressive extraction methods can degrade the chains and degree of branching [125]. Therefore, it is better to use gentler methods over a single step aggressive plan to avoid destroying the molecule and reducing its effect. Methods can be chemical, physical, and enzymatic; glass beads can be used to physically rupture the cell wall on specific enzymes and be used to break down the cell wall. Freezing and unfreezing are other methods used to rupture the cell wall [126]. \(\beta\)-glucans exhibit a wide range of properties, including solubility, primary structure, molecular weight, branching, and polymer charge. All of which affect biological activities. Low purity and variability of materials prevent understanding polysaccharide structure-function interactions with cells [127; 128]. The correct extraction method is fundamental for activity. Crude polysaccharides can be extracted using water, physical means (ultrasound and radiation), chemical methods (hot alkali and acid-alkali), natural ways (enzyme method), or a combination of the preceding techniques. Deproteinisation procedures include trichloroacetic acid (T.C.A. ), enzymes, and polysaccharide purification by column chromatography or ultrafiltration [129; 130; 131; 132; 133]. Ultrasound-assisted extraction (UAE) is a green extraction technique that avoids using strong solvents [134]. UAE accelerates the extraction of molecules but also preserves the structural and molecular characteristics [135]. Ultrasounds (US) are mechanical waves having a frequency over 20 kHz. Two types of US exist: low-intensity and high-intensity US. The low-intensity US is used to test physicochemical properties in the food industry. For the extraction of chemicals of interest, high-intensity ultrasounds are used at frequencies of 20-100 kHz [135]. The effect of operational variables on the UAE \(\beta\)-glucans from barley was investigated in a study by [PERSON] et al. (2013). The operational variables used in this investigation were amplitude, time, and cycles in conjunction with varied ultrasonic powers to increase extraction performance and molecular weight in beta-glucan extraction. The extraction performance is closely related to amplitude and time. When compared to conventional extraction, UAE reduces extraction times and energy usage. The data show that extraction yield relies on amplitude and time, whereas molecular weight decreases with time. The highest extraction yield (66%) is obtained by supplying the most energy (962.5 kJ/L), resulting in the lowest molecular weight (269 kDa). Reduced treatment intensity (energy output of 170 kJ/L) reduces extraction yield to 44.3% but raises molecular weight to 461 kDa. However, while the UAE process improves the extraction yield and molecular weight of \(\beta\)-glucans over stirred tank extraction (3 h, 55 \({}^{\circ}\)C, 1000 rpm), the main effect of ultrasounds is the reduction in process time and energy consumption (3 min versus 3 h and 170 kJ/L versus 1460 kJ/L) [136]. Another similar study determined parameters of UAE of polysaccharides from white button mushrooms (_A. bisporus_). The efficient extraction parameters were 230 W ultrasonic power, 70 \({}^{\circ}\)C extraction temperature, 62 min extraction duration, and 30 mL/g W/M ratio, yielding 6.02% _A. bisporus_ polysaccharides (ABPS). ABPS had a molecular weight of 158 kDa [137].