Valorization of brewer's yeast using Deep Eutectic Solvents pretreatment for fractionation and separation of cell wall polysaccharides

Beer yeast is an excellent source of beta-glucans or mono-and oligosaccharides, which have various biological and technical functional properties and can be used as food ingredients. The steps involved in extracting beta-glucan from beer yeast cells, such as cell wall disruption and purification, have notable effects on the compound's yield, cost, and various properties, including biological, physicochemical, and technical aspects. In this study, by comparing the extraction efficiencies of 6 synthetic deep eutectic solvents (DESs) for beta-glucan in brewer's yeast, it was found that using DES composed of choline chloride and lactic acid resulting in the yield and purity of insoluble beta-glucan (IBG) was 1.30 g/g and 49.3%. Even after one cycle of DES, IBG could still be separated with a yield of 0.26 g/g and a purity of 39.1%. Additionaly, the molecular weight of IBG separated by the DES method was 1.0-1.6 kDa, significantly lower than the range obtained using the traditional alkali-alcohol separation method (39.8-656 kDa). The results suggest an alternative use of DES for spent beer yeast byproduct extraction.