# \(\beta\)-Glucans from Yeast--Immunomodulators from Novel Waste Resources
## 3 Production of Yeast \(\beta\)-Glucans from Waste Streams  
Biotechnological and commercial interest in the manufacture of yeast is continuing to grow for applications including food, livestock feed, medicinal, cosmetic, and wastewater treatment applications [30]. Numerous cultivation variables, such as the type and availability of carbon and nitrogen sources, the cultivation temperature, pH, degree of aeration, osmotic pressure,time of incubation and growth phase, and mode of yeast propagation all affect the content and characteristics of structural polymers in the yeast cell wall [31; 32; 33]. The polymerisation of yeast \(\beta\)-glucans depends on external factors, including the growth phase and carbon source [34]. The chemical structure and concentration of the polysaccharide are also determined by the species' genetic profile [35]. Thus, yeast \(\beta\)-glucans have a variety of lengths, which may be quantified analytically. Conventional chemical characterisation techniques include Fourier transform infrared (FT-IR) and Nuclear magnetic resonance (1\({}_{\mathrm{H}}\)NMR) which determine the structure of a molecule [36]. The characterisation is vital as the chemical structure and function will all have effects on the immune counterpart interaction. Yeast may be quickly grown in a variety of different growth conditions. The biomass of food-grade yeasts is chiefly produced using traditional substrates such as molasses, a byproduct of the sugar industry. Additionally, starch, distiller's wash, whey, fruit and vegetable wastes, and unusual materials such as petroleum byproducts can also be used [37]. Although yeast \(\beta\)-glucans are usually produced in laboratories using biotechnological processes, they can also be sourced as byproducts from industrial processes. The environmental impact of industrial wastes derived from food sources is a challenge, reuse and disposal options are continuously being researched and tested. Byproducts of the food sector, potato juice and glycerol are two examples, are rich in nutrients and can be used as a digestate for microorganisms through recycling. Potato juice and glycerol are byproducts of the manufacturing of potato starch and biodiesel, respectively [38; 39]. These two byproducts were utilised in research by [PERSON] et al. (2015) to develop yeast, alter the cell wall structure, and acquire yeast biomass, eventually increasing the amounts of (1,3)/(1,6)-glucans. Interestingly, the Y.B.D medium, deproteinated potato juice, and 5-10% glycerol as a carbon source enhanced \(\beta\)-glucans synthesis from 31% to 44% [40]. [PERSON] et al. (2021) studied the effects of tannic acid on _Saccharomyces carlsbergenis_, a brewer's yeast. Beer fermentation produces a lot of waste. Tannins are utilised in brewing while mashing the hot wort. Tannins interact with the yeast cell wall to form polysaccharides and cause stress in yeast cells which is counteracted by a buildup of \(\beta\)-glucans in the cell wall. Tannic acid increases the thickness of the \(\beta\)-glucan-chitin layer while decreasing the manoprotein layer. Thicker cell walls correspond with higher carbohydrate and \(\beta\)-glucan levels. The addition of 0.1% w/v tannic acid boosted \(\beta\)-glucan synthesis and content by 42.23%. The stirred tank culture produced 1.4 times more \(\beta\)-glucans than the shaking flask culture [41; 42; 43]. A novel source for the commercial synthesis of yeast \(\beta\)-glucans was investigated by [PERSON] et al. (2016). The group isolated \(\beta\)-glucans for the first time from winery spent yeast biomass. During the winemaking process, a byproduct known as wine lees is produced. Most byproducts include spent yeasts, bacteria, tartaric acid, ethanol, phenolics, and pigments. Thus, \(\beta\)-glucans can be sourced from the yeast waste biomass that accumulates in wine tanks throughout the winemaking process. This study showed that the isolated \(\beta\)-glucans contained some amount of tartaric acid and polyphenols, which could not be omitted.