Yeast (Saccharomyces cerevisiae): evaluation of cellular disruption processes, chemical composition, functional properties and digestibility

Cost-effective urine recycling enabled by a synthetic osteoyeast platform for production of hydroxyapatite

Recycling human urine offers a sustainable solution to environmental challenges posed by conventional wastewater treatment. While it is possible to recover nutrients like nitrogen and phosphorus from urine, the low economic value of these products limits large-scale adoption. Here, we show that engineered yeast can convert urine into hydroxyapatite (HAp), a high-value biomaterial widely used in bone and dental applications. Inspired by the biological mechanisms of bone-forming cells, we develop a synthetic yeast platform osteoyeast, which uses enzymes to break down urea and increase the pH of the surrounding environment. This triggers the yeast vacuoles to accumulate calcium and phosphate as amorphous calcium phosphate, which is then secreted in vesicles and crystallized into HAp. We achieve HAp production at titers exceeding 1 g/L directly from urine. Techno-economic analysis demonstrates that this process offers clear economic and environmental advantages, making it a compelling strategy for high-value resource recovery from human waste.

Beta-Glucans in Biotechnology: A Holistic Review with a Special Focus on Yeast

Beta-glucans (β-glucans) are polysaccharides with significant biological activity, widely recognized for their immunomodulatory, anti-inflammatory, and metabolic health benefits. Among various sources, yeast-derived β-(1 → 3), (1 → 6)-glucans have gained particular attention due to their potent bioactivity and diverse applications in biotechnology, pharmaceuticals, and functional foods. This review comprehensively examines yeast β-glucans, covering their biosynthesis, extraction, and purification from industrially relevant yeast strains, particularly Saccharomyces cerevisiae. The impact of fermentation parameters on β-glucan yield and structural properties is analyzed, highlighting advancements in optimizing microbial production. Furthermore, we discuss methods for characterizing yeast β-glucans, including analytical and bioassay techniques, and compare their physicochemical properties with those of β-glucans from other sources. Finally, this review explores the therapeutic potential of yeast-derived β-glucans, focusing on their role in immunomodulation and metabolic regulation and their emerging applications in biomedicine, functional foods, and industrial formulations. By synthesizing recent advancements, this work provides insights into the expanding utilization of yeast β-glucans and their potential for future biotechnological developments.

Power-to-vitamins: producing folate (vitamin B9) from renewable electric power and CO2 with a microbial protein system

We recently proposed a two-stage Power-to-Protein technology to produce microbial protein from renewable electric power and CO2. Two stages were operated in series: Clostridium ljungdahlii in Stage A to reduce CO2 with H2 into acetate, and Saccharomyces cerevisiae in Stage B to utilize O2 and produce microbial protein from acetate. Renewable energy can be used to power water electrolysis to produce H2 and O2. A drawback of Stage A was the need for continuous vitamin supplementation. In this study, by using the more robust thermophilic acetogen Thermoanaerobacter kivui instead of C. ljungdahlii, vitamin supplementation was no longer needed. Additionally, S. cerevisiae produced folate when grown with acetate as a sole carbon source, achieving a total folate concentration of 6.7 mg per 100 g biomass with an average biomass concentration of 3 g l-1. The developed Power-to-Vitamin system enables folate production from renewable power and CO2 with zero or negative net-carbon emissions.

Spent Brewer's Yeast Lysis Enables a Best Out of Waste Approach in the Beer Industry

Yeasts have emerged as an important resource of bioactive compounds, proteins and peptides, polysaccharides and oligosaccharides, vitamin B, and polyphenols. Hundreds of thousands of tons of spent brewer's yeast with great biological value are produced globally by breweries every year. Hence, streamlining the practical application processes of the bioactive compounds recovered could close a loop in an important bioeconomy value-chain. Cell lysis is a crucial step in the recovery of bioactive compounds such as (glyco)proteins, vitamins, and polysaccharides from yeasts. Besides the soluble intracellular content rich in bioactive molecules, which is released by cell lysis, the yeast cell walls β-glucan, chitin, and mannoproteins present properties that make them good candidates for various applications such as functional food ingredients, dietary supplements, or plant biostimulants. This literature study provides an overview of the lysis methods used to valorize spent brewer's yeast. The content of yeast extracts and yeast cell walls resulting from cellular disruption of spent brewer's yeast are discussed in correlation with the biological activities of these fractions and resulting applications. This review highlights the need for a deeper investigation of molecular mechanisms to unleash the potential of spent brewer's yeast extracts and cell walls to become an important source for a variety of bioactive compounds.

Factors Affecting Yeast Digestibility and Immunostimulation in Aquatic Animals

The aquafeed industry increasingly relies on using sustainable and appropriate protein sources to ensure the long-term sustainability and financial viability of intensive aquaculture. Yeast has emerged as a viable substitute protein source in the aquaculture sector due to its potential as a nutritional supplement. A substantial body of evidence exists to suggest that yeast has the potential to act as an effective immune-stimulating agent for a range of aquaculture fish species. Furthermore, the incorporation of yeast supplements and feed additives has the potential to bolster disease prevention, development, and production within the aquaculture sector. Except for methionine, lysine, arginine, and phenylalanine, which are typically the limiting essential amino acids in various fish species, the various yeast species exhibit amino acid profiles that are advantageous when compared to fishmeal. The present review considers the potential nutritional suitability of several yeast species for fish, with particular attention to the various applications of yeast in aquaculture nutrition. The findings of this study indicate that the inclusion of yeast in the diet resulted in the most favorable outcomes, with improvements observed in the overall health, growth performance, and nutritional condition of the fish. Digestibility, a key factor in sustainable feed development, is discussed in special detail. Additionally, this review addresses the utilization of yeast as an immunostimulating agent for fish and its digestion in fish. Furthermore, the research emphasizes the necessity of large-scale production of yeast as a substitute for fishmeal in aquaculture.

Characterization of yeast protein isolates extracted via high-pressure homogenization and pH shift: A promising protein source enriched with essential amino acids and branched-chain amino acids

In the global food industry, plant-based protein isolates are gaining prominence as an alternative to animal-based counterparts. However, their nutritional value often falters due to insufficient essential amino acids. To address this issue, our study introduces a sustainable protein isolate derived from yeast cells, achieved through high-pressure homogenization (HPH) and alkali pH-shifting treatment. Subjected to HPH pressures ranging from 60 to 120 MPa and 1 to 10 cycles, higher pressure and cycle numbers resulted in enhanced disruption of yeast cells. Combining HPH with alkali pH-shifting treatment significantly augmented protein extraction. Four cycles of HPH at 100 MPa yielded the optimized protein content, resulting in a yeast protein isolate (YPI) with 75.3 g protein per 100 g powder, including 30.0 g of essential amino acids and 18.4 g of branched-chain amino acids per 100 g protein. YPI exhibited superior water and oil-holding capacities compared to pea protein isolate, whey protein isolate (WPI), and soy protein isolate. Although YPI exhibited lower emulsifying ability than WPI, it excelled in stabilizing protein-stabilized emulsions. For foaming, YPI outperformed others in both foaming ability and stabilizing protein-based foam. In conclusion, YPI surpasses numerous plant-based protein alternatives in essential amino acids and branched-chain amino acids contents, positioning it as an excellent candidate for widespread utilization as a sustainable protein source in the food industry, owing to its exceptional nutritional advantages, as well as emulsifying and foaming properties. PRACTICAL APPLICATION: This study introduces a sustainable protein isolate derived from yeast cells. YPI exhibited considerable promise as a protein source. Nutritionally, YPI notably surpassed plant-based protein isolates in EAA and BCAA contents. Functionally, YPI demonstrated superior water-holding and oil-holding capacities, as well as an effective emulsion and foam stabilizer.

Wheat craft beer made from AFB1-contaminated wheat malt contains detectable mycotoxins, retains quality attributes, but differs in some fermentation metabolites

Levels of aflatoxin B1 (AFB1) were measured during the production of wheat craft beer made with wheat malt contaminated with AFB1 (1.23 µg/kg). A wheat craft beer made with non-contaminated wheat malt was produced for comparison purposes. AFB1 was measured after mashing (malt after the mashing process), and in spent grain (spent grains are filtered to collect the wort - remaining sugar-rich liquid), sweet wort, green beer, spent yeast, and in beer. Physicochemical parameters (pH, titratable acidity, color parameters, total soluble solids), sugars, organic acids, alcohols, and phenolics were evaluated after mashing, and in sweet wort, green beer, and beer samples. Density and yeast counts were determined over 120 h of sweet wort fermentation every 24 h. The AFB1 levels in the final beer were 0.22 µg/L, while the spent grains and spent yeasts contained 0.71 ± 0.17 and 0.11 ± 0.03 µg/kg of AFB1, respectively. AFB1 contamination did not influence the final product's physicochemical parameters, density during fermentation, fructose, or glycerol content. Higher yeast counts were observed during the first 48 h of non-contaminated wheat craft beer fermentation, with higher ethanol, citric acid, and propionic acid contents and lower glucose, malic acid, and lactic acid contents compared with beer contaminated with AFB1. Non-contaminated wheat craft beer also had higher concentrations of gallic acid, chlorogenic acid, catechin, procyanidin A2, and procyanidin B1. AFB1 contamination of wheat malt may not affect basic quality parameters in wheat craft beer but can influence the final product's organic acid and phenolic contents. Our findings show that if wheat craft beer is made with contaminated malt, AFB1 can remain in the final product and may pose a risk to consumers.

Dual-Pulsed Laser Ablation of Oyster Shell Producing Novel Thin Layers Deposed to Saccharomyces cerevisiae

Dual-pulsed (DPL) laser deposition using oyster shells as targets was studied in order to find out if this method can replace the use of high-power pulsed lasers. Aspects related to changes in the morphological structure of the thin layer but also to the chemical composition of the obtained thin layer were analyzed and compared with the target as well as with the thin layers obtained with a higher power pulsed laser in a single-pulsed (SPL) regime. Orthorhombic structures were noticed with Scanning Electron Microscopy for the thin film obtained in DPL mode compared to the irregular particles obtained in SPL mode. The deacetylation process during ablation was evidenced by Fourier Transform Infrared spectroscopy, resulting in chitosan-based thin films. The effect of the obtained thin films of chitosan on the cells of baker's yeast (Saccharomyces cerevisiae) was studied. Restoration of the yeast paste into initial yeast was noticed mainly when the hemp fabric was used as support for the coating with yeas which was after that coated with chitosan thin film produced by DPL method.

Trends and prospects in dairy protein replacement in yogurt and cheese

There is a growing demand for nutritional, functional, and eco-friendly dairy products, which has increased the need for research regarding alternative and sustainable protein sources. Plant-based, single-cell (SCP), and recombinant proteins are being explored as alternatives to dairy proteins. Plant-Based Proteins (PBPs) are commonly used to replace total dairy protein. However, PBPs are generally mixed with dairy proteins to improve their functional properties, which makes them dependent on animal protein sources. In contrast, single-Cell Proteins (SCPs) and recombinant dairy proteins are promising alternatives for dairy protein replacement since they provide nutritional components, essential amino acids, and high protein yield and can use industrial and agricultural waste as carbon sources. Although alternative protein sources offer numerous advantages over conventional dairy proteins, several technical and sensory challenges must be addressed to fully incorporate them into cheese and yogurt products. Future research can focus on improving the functional and sensory properties of alternative protein sources and developing new processing technologies to optimize their use in dairy products. This review highlights the current status of alternative dairy proteins in cheese and yogurt, their functional properties, and the challenges of their use in these products.

Effects of brewer's spent yeast inclusion level and ensiling duration on fermentative, fungal load dynamics, and nutritional characteristics of brewer's spent yeast-based silage

Objective

This study was conducted to evaluate the effect of brewer's spent yeast (BSY) inclusion level and ensiling duration (ED) on fermentative, fungal load dynamics, and nutritional characteristics of brewer's spent-yeast based silage.

Materials and methods

To prepare the silages materials, 4 BSY inclusion levels (0, 10, 20, and 30%) to replace BSG and 3 ED (2,4 and 6 weeks) were arranged in 4 × 3 factorial combination using a completely randomized design (CRD) in 5 replications. The ratio of brewery spent grain (BSG) to wheat bran (WB) used majorly as protein and energy sources, respectively was 30:69 with a 1% salt addition. Parameters measured include observation for surface spoilage, yeast and mold colony count, silage temperature, pH, total dry matter loss (TDML), major proximate, detergent fractions and permanganate lignin, in-vitro organic matter digestibility (IVOMD) and estimated metabolizable energy (EME) values.

Results

The study revealed that at any BSY inclusion level and ED, extensive mold growths and discolorations were not observed. However, slightly higher values of 6.5, 5.7, and 12.2 colonies forming unit (CFU)/g DM yeast, mold, and total fungal counts (TFC), respectively were recorded only at the 6 weeks of the fermentation period with 30% BSY inclusion level. Brewer's spent yeast inclusion level and ED had a significant (P < 0.05) effect on silage temperature (mean = 18.05 °C) and pH (mean = 4.16). Among proximate and detergent values, crude protein (mean CP g/kg DM = 204.5), neutral detergent fiber (mean NDF g/kg DM = 552.9), and acid detergent fiber (mean ADF g/kg DM = 115.9) responded significantly (P < 0.05) to both BSY inclusion levels and ED.

Conclusion

Among nutritional quality, CP, IVOMD, and EME of silage samples were subjected to substantial improvements when silage masses were prepared from 20% BSY inclusion levels and when the same silage materials were allowed to ferment for four weeks. In addition, the lab-based experiment should be supported with additional silage quality parameters like volatile fatty acid content of the silage materials and supplementation of ruminant livestock under both on-station and on-farm conditions using either a pilot and/or target animals.

Proteases as Tools for Modulating the Antioxidant Activity and Functionality of the Spent Brewer's Yeast Proteins

The functionality of the peptides obtained through enzymatic hydrolysis of spent brewer's yeast was investigated. Hydrolysis was carried out for 4-67 h with bromelain, neutrase and trypsin. The resulting hydrolysates were characterized in terms of physical-chemical, antioxidant and techno-functional properties. The solid residues and soluble protein contents increased with the hydrolysis time, the highest values being measured in samples hydrolyzed with neutrase. Regardless of the hydrolysis time, the maximum degree of hydrolysis was measured in the sample hydrolyzed with neutrase, while the lowest was in the sample hydrolyzed with trypsin. The protein hydrolysate obtained with neutrase exhibited the highest DPPH radical scavenging activity (116.9 ± 2.9 μM TE/g dw), followed by the sample hydrolyzed with trypsin (102.8 ± 2.7 μM TE/g dw). Upon ultrafiltration, the fraction of low molecular weight peptides (<3 kDa) released by bromelain presented the highest antioxidant activity (50.06 ± 0.39 μM TE/g dw). The enzymes influenced the foaming properties and the emulsions-forming ability of the hydrolysates. The trypsin ensured the obtaining of proteins hydrolysate with the highest foam overrun and stability. The emulsions based on hydrolysates obtained with neutrase exhibited the highest viscosity at a shear rate over 10 s^-1. These results indicate that the investigated proteases are suitable for modulating the overall functionality of the yeast proteins.

Valorization of Spent Brewer’s Yeast for the Production of High-Value Products, Materials, and Biofuels and Environmental Application

Spent brewer’s yeast (SBY) is a byproduct of the brewing industry traditionally used as a feed additive, although it could have much broader applications. In this paper, a comprehensive review of valorization of SBY for the production of high-value products, new materials, and biofuels, as well as environmental application, is presented. An economic perspective is given by mirroring marketing of conventional SBY with innovative high-value products. Cascading utilization of fine chemicals, biofuels, and nutrients such as proteins, carbohydrates, and lipids released by various SBY treatments has been proposed as a means to maximize the sustainable and circular economy.

Spent Yeast Valorization for Food Applications: Effect of Different Extraction Methodologies

Over the years, synthetic biology has been growing with the use of engineered yeast strains for the production of sustainable ingredients to meet global healthcare, agriculture, manufacturing and environmental challenges. However, as seen from the brewing industry perspective, these processes generate a substantial amount of spent yeast that contains high nutritional value related to its high protein content, showing its potential to be used as an alternative protein source. Taking into account the rising demand for protein because of the growth in the global population, the present study aims to produce peptide-rich extracts by different potentially scalable and sustainable methodologies in a circular economy approach for the food and nutraceutical industries. The results demonstrated that extraction from genetically modified strains allowed the production of extracts with an excellent nutritional profile and low molecular weight peptides. Furthermore, autolysis was shown to be a potential sustainable approach for this production, though other green metrics need to be explored in order to establish this process at an industrial level.

Incorporation of natural and mechanically ruptured brewing yeast cells in beef burger to replace textured soy protein

The use of brewer`s yeast to replace textured soy protein (TSP) in burgers was investigated. Three formulations were made, corresponding to a control formulation with 4% TSP, a formulation containing 4% yeast cells in their natural state, and a formulation made with 4% mechanically ruptured yeast cells, which were characterized for the chemical, technological, and sensory properties. Significant differences were observed for pH and instrumental color between the formulations, with no changes in the visual color evaluation by the untrained assessors. The addition of yeast cells resulted in a higher cooking yield and lower reduction in diameter, contributing to maintaining the shape and juiciness of burgers, which is a positive aspect from the technological point of view. The TSP-based formulation presented higher overall appearance and flavor scores when compared with the other formulations, with no significant differences for the other sensory attributes. The results showed that debittering of yeast-cell biomass is required to remove hop resins and tannins before using in burgers, aimed to improve the product`s acceptance and the purchase intent. The debittered yeast cell biomass can be used in burger formulations with great potential to replace TSP, as an alternative to obtain a free allergen meat product.

Biocatalysis in the Chemistry of Lupane Triterpenoids

Pentacyclic triterpenes are important representatives of natural products that exhibit a wide variety of biological activities. These activities suggest that these compounds may represent potential medicines for the treatment of cancer and viral, bacterial, or protozoal infections. Naturally occurring triterpenes usually have several drawbacks, such as limited activity and insufficient solubility and bioavailability; therefore, they need to be modified to obtain compounds suitable for drug development. Modifications can be achieved either by methods of standard organic synthesis or with the use of biocatalysts, such as enzymes or enzyme systems within living organisms. In most cases, these modifications result in the preparation of esters, amides, saponins, or sugar conjugates. Notably, while standard organic synthesis has been heavily used and developed, the use of the latter methodology has been rather limited, but it appears that biocatalysis has recently sparked considerably wider interest within the scientific community. Among triterpenes, derivatives of lupane play important roles. This review therefore summarizes the natural occurrence and sources of lupane triterpenoids, their biosynthesis, and semisynthetic methods that may be used for the production of betulinic acid from abundant and inexpensive betulin. Most importantly, this article compares chemical transformations of lupane triterpenoids with analogous reactions performed by biocatalysts and highlights a large space for the future development of biocatalysis in this field. The results of this study may serve as a summary of the current state of research and demonstrate the potential of the method in future applications.

Spent brewer's yeast as a source of high added value molecules: a systematic review on its characteristics, processing and potential applications

Development of new strategies to add-value to agro-industrial by-products are of environmental and economical importance. Innovative and low-cost sources of protein and bioactive peptides have been explored worldwide. Spent brewer's yeast (SBY) is the second most relevant by-product from the brewing industry, and despite its nutritional (about 50% protein, dry weight) and technological potential, it is still underused or needs to be disposed of. SBY cells need to be disrupted to release intracellular and cell wall proteins. This procedure has been performed using autolysis, glass bead milling, enzymatic hydrolysis and ultrasound processing. Enzymatic treatment is usually performed without prior purification and is a challenging process, which involves multiple factors, but has been successfully used as a strategy to add value to agro-industrial by-products. Scope and approach: in this review, we particularly focused on enzymatic hydrolysis as a strategy to promote SBY valorisation, illustrating the state-of-the-art processes used to produce protein extracts from this material as well as exploring fundamental concepts related to the particularities of yeast cell disruption and protein hydrolysis. Furthermore, innovative applications of value-added yeast by-products in food, biotechnological and pharmaceutical industries are presented and discussed. Key findings and conclusions: the discovery of valuable compounds found in spent yeasts as well as the development of new processing methodologies have been widening the possibilities of reuse and transformation of SBY as an ingredient and innovative matrix. Once released, yeast proteins and peptides may be applied as an innovative non-animal protein source or a functional and bioactive ingredient.