Spent Yeast from Brewing Processes: A Biodiverse Starting Material for Yeast Extract Production

Abstract

Spent yeast from beer manufacturing is a cost-effective and nutrient-rich starting material for the production of yeast extracts. In this study, it is shown how physiologically important ingredients in a yeast extract are influenced by the composition of the spent yeast from the brewing process. In pilot fermentations, the time of cropping (primary fermentation, lagering) of the spent yeast and the original gravity (12 • P, 16 • P, 20 • P) of the fermentation medium was varied, and four alternative non-Saccharomyces yeast strains were compared with two commercial Saccharomyces yeast strains. In addition, spent yeast was contaminated with the beer spoiler Lactobacillus brevis. The general nutrient composition (total protein, fat, ash) was investigated as well as the proteinogenic amino acid spectrum, the various folate vitamers (5-CH 3 -H 4 folate, 5-CHO-H 4 folate, 10-CHO-PteGlu, H 4 folate, PteGlu) and the biological activity (reduction, antioxidative potential) of a mechanically (ultrasonic sonotrode) and an autolytically produced yeast extract. All the investigated ingredients from the yeast extract were influenced by the composition of the spent yeast from the brewing process. The biodiversity of the spent yeast from the brewing process therefore directly affects the content of physiologically valuable ingredients of a yeast extract and should be taken into consideration in industrial manufacturing processes. cell that remains once the cell wall has been destroyed and removed [4][5][6]. The variety of different physiologically valuable substances in yeast cells offers the possibility of using them as yeast extract in different areas of the food industry [3,7]. As "yeast food", these extracts can therefore increase the free α-amino nitrogen (FAN) when fermenting beer worts with a high content of unmalted grains [8] or a high extract content (high-gravity worts) [9,10], and consequently improve the yeast's nutrient supply and fermentation performance [11,12]. Free proteinogenic amino acids supply the majority of the FAN [12]. The quantity and composition of the relevant amino acids are ultimately critical to performance during fermentation [13] and also impact the beer's aroma profile [14]. From a nutritional standpoint, yeast extracts from spent yeast supply a high concentration of essential and semi-essential amino acids for human beings [5,7]. Yeast extracts are also a good source of B vitamins [6,15]. Among these, the various naturally occurring folate vitamers play an essential role in the human diet, with the biologically active form 5-methyltetrahydrofolate (5-CH 3 -H 4 folate) fulfilling key metabolic tasks in human cells [16]. The bioactivity of yeast extracts, which is demonstrated in the form of reduction and anti-oxidative potential, also makes these extracts particularly interesting for the food industry [6,7,15,17].The majority of globally produced beer is manufactured by fermenting high-gravity worts [18]. The extract content of the wort is increased by adding sugar syrup, which modifies the nutr...

More than just a beer—the potential applications of by-products from beer manufacturing in polymer technology

“…Another broadly investigated application of spent yeast is cultivating microorganisms and other biotechnological processes [230,231]. Due to the beneficial composition of brewery spent yeast, various microorganisms cultivated on this by-product may grow noticeably faster than other yeast types, as reported by Ferreira et al [232].…”

Spent Brewer’s Yeast as a Source of Insoluble β-Glucans

“…Mainly used in animal feed, the application of various pretreatment processes can make residual yeasts a product with multiple uses for human consumption as follows: enhance or impart a meaty flavor to food [ 5 , 6 ]; an alternative protein source [ 7 ]; folate-rich yeast extract (depending on the type of yeast) [ 8 ]; as a water-insoluble polysaccharide, such as β-glucan with increased potential in the pharmaceutical and food industry [ 9 , 10 ].…”

Metabolic engineering of Escherichia coli W for isobutanol production on chemically defined medium and cheese whey as alternative raw material

“…The high concentrations that need to be applied could limit the use of this media additive. Alternatively, yeast extract could also be purchased at lower prices from breweries, where yeast is a main by-product [ 60 , 61 ]. However, yeast biomass is from fermentation processes is frequently used as an animal feedstock.…”

“…It seems likely that the availability of yeast biomass for a fermentation process yielding a low-price product such as isobutanol is therefore limited in comparison to the higher price that can be obtained when sold as an animal feedstock. Additionally, variations in yeast extract quality could affect process performance and different brewing processes were shown to influence the nutrient composition [ 60 ]. Due to additional costs related to the use of a complex media additive, it is more cost-effective to omit additional media components.…”