# Potential Applications of Yeast Biomass Derived from Small-Scale Breweries
## 6 Spent Yeast Derivatives--Potential Applications  
The burgeoning global population, coupled with diminishing expanses of available land for agricultural pursuits, presents a formidable challenge. Concurrently, the escalating demand for portable water is accentuated by dwindling water reservoirs in numerous agricultural regions year after year. While plants stand as invaluable nutritional sources of protein, their cultivation necessitates extensive acreage and substantial water resources. Conversely, animal protein entails a significantly prolonged acquisition period, and its amino acid profile does not markedly differ from that of yeast protein. In many regions, animal protein remains scarcely accessible, with its cost often surpassing the financial means of the populace. Recent years have witnessed a substantial decline in the supply of the most prevalent animal proteins, such as bovine milk protein, attributable to plummeting prices and protracted regional policies enforcing production constraints [48]. A potential solution to satisfying humanity's need for proteinaceous products lies in proteins synthesized by diverse microorganisms, including bacteria, yeast, algae, and fungi [49]. Among the economical protein sources is post-fermentative yeast biomass, a by-product of the brewing industry that boasts up to 49% protein content in dry matter. Proteins derived from brewing yeasts exhibit notable bioavailability, rendering them a sustainable protein alternative and a hypoallergenic choice for vegans and vegetarians. Given their origin as by-products, they also emerge as a superior alternative relative to plant or animal proteins, known for their more resource-intensive production. Currently, grain meal (mainly soybean) dominates as the primary protein source in feed production. However, a proposition advocates for the substitution of plant-based feeds with microbial biomass in animal diets, including post-fermentative yeast biomass, potentially up to 100%. Owing to their vitamin and mineral content, high protein levels, and bioavailability, brewing yeasts find frequent applications as feed additives. Observable effects from studies encompass heightened immunity, enhanced milk production parameters, and a favorable influence on animal health attributable to an improved intestinal microflora [50; 51]. Supplementing feed mixtures with brewing yeast (ranging from 1% to 5%) in broiler diets effectively ameliorated the adverse effects of diets characterized by vitamin and mineral deficiencies, culminating in enhanced bone health in these animals [52]. Consequently, brewing yeasts find extensive utility as food additives, not merely as an economical protein source but also in the form of yeast extract obtained through enzymatic processing. This extract is employed as a flavor enhancer, featuring components such as monosodium glutamate (MSG) and nucleotides like 5\({}^{\prime}\)-guanosine monophosphate (5\({}^{\prime}\)-GMP) and 5\({}^{\prime}\)-inosine monophosphate (5\({}^{\prime}\)-IMP). Such extracts, comprising monosodium glutamate and nucleotides, are deployed in the meat industry and the production of diverse food items such as sauces, soups, crackers, and chips [53]. The nutritional value of yeast protein is determined through its amino acid composition, with paramount importance ascribed to the group of eight essential amino acids--isoleucine, leucine, lysine, phenylalanine, methionine, threonine, tryptophan, and valine. These amino acids, unsynthesized by humans, are necessary in the diet [54]. In the amino acid profile of yeast protein, the quantities of individual amino acids, including isoleucine, leucine, lysine, phenylalanine, threonine, and valine, surpass the World Health Organization's (WHO) recommended standards for human diets (Table 4). The optimal protein content in the human diet exceeds 40% [48]. Consequently, 100 g of dry yeast biomass encapsulates up to 49 g of protein, precisely aligning with nearly 100% of the recommended daily intake for adults (50 g) [55].