Yeast Slurry Research Articles

Hydrothermal conditioning of oleaginous yeast cells to enable recovery of lipids as potential drop-in fuel precursors

BackgroundLipids produced using oleaginous yeast cells are an emerging feedstock to manufacture commercially valuable oleochemicals ranging from pharmaceuticals to lipid-derived biofuels. Production of biofuels using oleaginous yeast is a multistep procedure that requires yeast cultivation and harvesting, lipid recovery, and conversion of the lipids to biofuels. The quantitative recovery of the total intracellular lipid from the yeast cells is a critical step during the development of a bioprocess. Their rigid cell walls often make them resistant to lysis. The existing methods include mechanical, chemical, biological and thermochemical lysis of yeast cell walls followed by solvent extraction. In this study, an aqueous thermal pretreatment was explored as a method for lysing the cell wall of the oleaginous yeast Rhodotorula toruloides for lipid recovery.ResultsHydrothermal pretreatment for 60 min at 121 °C with a dry cell weight of 7% (w/v) in the yeast slurry led to a recovery of 84.6 ± 3.2% (w/w) of the total lipids when extracted with organic solvents. The conventional sonication and acid-assisted thermal cell lysis led to a lipid recovery yield of 99.8 ± 0.03% (w/w) and 109.5 ± 1.9% (w/w), respectively. The fatty acid profiles of the hydrothermally pretreated cells and freeze-dried control were similar, suggesting that the thermal lysis of the cells did not degrade the lipids.ConclusionThis work demonstrates that hydrothermal pretreatment of yeast cell slurry at 121 °C for 60 min is a robust and sustainable method for cell conditioning to extract intracellular microbial lipids for biofuel production and provides a baseline for further scale-up and process integration.Graphical abstract

Yeast Expressing a Phage Endolysin Reduces Endogenous Clostridium perfringens Ex Vivo in 21-Day-Old Broiler Chicken Intestinal Fluids.

The phage endolysin PlyCP41 when purified from Escherichia coli exhibits lytic activity against Clostridium perfringens (CP) in vitro. The anti-clostridial activity of PlyCP41 endolysin expressed in transgenic yeast (Saccharomyces cerevisiae) was verified in phosphate buffered saline via mixing experiments with cultured CP and transgenic yeast slurries followed by serial dilution plating and colony counts on tryptose sulfite cycloserine (CP indicator) plates. The transgenic yeast containing PlyCP41 resulted in a log10 4.5 reduction (99.997%; P < 0.01) of the cultured CP. In addition, this serial dilution plating assay was used to demonstrate that transgenic yeast slurries could reduce the endogenous CP content in fluids from three different gastrointestinal regions (proximal, medial, and distal) from 21-day-old broiler chickens. The transgenic yeast treatment of gut slurries resulted in a log 10 1.19, 4.53, and 1.28 reduction in proximal, medial, and distal gut slurries (90% to 99.99% of the endogenous CP; P < 0.01), respectively, compared to nontreatment controls. These results indicate that the phage endolysin PlyCP41 expressed in S. cerevisiae is effective at reducing the endogenous CP in gastrointestinal fluids of broiler chickens. Future studies will measure the anti-CP effect in vivo by administering transgenic yeast to broiler chickens in the feed.

Potential Applications of Yeast Biomass Derived from Small-Scale Breweries

Yeast biomass, a brewery by-product of the world’s substantial alcohol beverage industry, finds successful applications in the fodder industry and food additive production. This is attributed to its rich nutritional profile that comprises high protein and vitamin content. Nonetheless, in small-scale breweries, yeast slurries present a significant challenge, as the quantities obtained are insufficient to attract the attention of the food industry. The disposal of yeast contributes substantially to the organic load of wastewater (approximately 40%) and elevates water consumption (3–6 hL/hL of beer), consequently escalating production costs and environmental impact. In recent years, diverse potential applications of products derived from yeast biomass have emerged, encompassing the substitution of sera in cell culture media, the fortification of animal feed with vitamins and selenium, the utilization of beta-glucan in low-fat food products, and the development of functional foods incorporating yeast-derived peptides. These peptides exhibit the potential to safeguard the gastric mucosa, prevent hypertension, and address neurodegenerative disorders. The rising demand for value-added products derived from yeast underscores the potential profitability of processing yeast from small breweries. Due to the high equipment costs associated with yeast biomass fractionation, the establishment of specialized facilities in collaboration with multiple small breweries appears to be the most optimal solution.

Lager Yeast Design Through Meiotic Segregation of a Saccharomyces cerevisiae × Saccharomyces eubayanus Hybrid.

Yeasts in the lager brewing group are closely related and consequently do not exhibit significant genetic variability. Here, an artificial Saccharomyces cerevisiae × Saccharomyces eubayanus tetraploid interspecies hybrid was created by rare mating, and its ability to sporulate and produce viable gametes was exploited to generate phenotypic diversity. Four spore clones obtained from a single ascus were isolated, and their brewing-relevant phenotypes were assessed. These F1 spore clones were found to differ with respect to fermentation performance under lager brewing conditions (15°C, 15 °Plato), production of volatile aroma compounds, flocculation potential and temperature tolerance. One spore clone, selected for its rapid fermentation and acetate ester production was sporulated to produce an F2 generation, again comprised of four spore clones from a single ascus. Again, phenotypic diversity was introduced. In two of these F2 clones, the fermentation performance was maintained and acetate ester production was improved relative to the F1 parent and the original hybrid strain. Strains also performed well in comparison to a commercial lager yeast strain. Spore clones varied in ploidy and chromosome copy numbers, and faster wort fermentation was observed in strains with a higher ploidy. An F2 spore clone was also subjected to 10 consecutive wort fermentations, and single cells were isolated from the resulting yeast slurry. These isolates also exhibited variable fermentation performance and chromosome copy numbers, highlighting the instability of polyploid interspecific hybrids. These results demonstrate the value of this natural approach to increase the phenotypic diversity of lager brewing yeast strains.

REPLACEMENT OF MAIZE WITH CASSAVA ROOT MEAL EITHER ALONE OR MIXED WITH BREWERS YEAST SLURRY IN DIETS FOR GROWING-FINISHING PIGS

Twenty four (24) crossbred grower pigs of Large White, Landrace, Hampshire and Duroc breeds, which averaged 43.96kg liveweight, were allocated in groups of4 pigs and two replicates, to each of 3 diets. Diet I was a maize-based control while in diets II and III, cassava root meal (CRM) solely, or its mixture with brewers yeast slurry (CRM-BYS) replaced all of the maize in the control. The pigs were group - housed in concrete floor pens where they were fed the test diets to appetite, and had water ad libitum over a 30-day period. Performance parameters were measured during this period, and at the end of it, 4 pigs from each treatment were slaughtered and their carcasses characterized. Average daily feed (ADF), average daily gain (ADG), feed/gain ratio for diets I, II and III were 2.08, 2.07, and 2.01 kg; 0.63, 0.60 and 0.64 kg; 331, 3.48 and 3.15 respectively. The differences were not significant (P &gt;.05). Feed cost/kg liveweight gain was significantly (P&lt; .05) reduced from N19.43 to N14.65 and N11.28 when dietary maize was replaced by CRM and CRM/BYS respectively. Linear and jointed carcass measures, and organ weight did not differ significantly (P&gt;.05) in the different diets. These data show a net advantage of replacing dietary maize with cassava root meal or its mixture with brewers yeast slurry for growing-finishing pigs under the defined conditions.

REPLACING MAIZE WITH CASSAVA ROOT MEAL OR ITS MIXTURE WITH BREWERS YEAST SLURRY IN RABBIT DIETS

Three diets were evaluated for their effect on performance, carcass yield and organ measurements of finisher rabbits. The control was maize-based (MC) while, in the other two diets, cassava root meal (CR) or its mixture with brewers yeast slurry (CYS) replaced the maize. Five approximately 9-week old crossbred (Chinchilla X California X New Zealand White) rabbits which averaged 930g livewight, were allocated to each diet and fed individually for 70days. The rabbits were then slaughtered and their dressed carcasses and organs weighed. At 70days of feeding, the average livewighed of rabbits fed MC, CR and CYS were 2120g, 2026g and 2098g respectively. Average daily feed intake, average daily gain and feed conversion ratio were 66.80g, 64.92g and 60.70g, 15.65g and 16.29g and 3.92g and 4.15 and 3.64 for the respective diets. Warm dressing % and organ weight as percent of empty carcass weight did not differ significantly (P &gt;0.05) among the diet. Kidney fat weight was lower (P &lt;0.05) for CYS than for MC and CR. Replacement of maize with CR in the diet lowered (P &lt; 0.05) rabbit performance while that with CYS allowed for more efficient utilization of the diet, and for leaner carcasses of rabbits

RESPONSE OF WEANER-GROWER PIGS TO DIETS CONTAINING SUN-DRIED MIXTURES OF BREWERS YEAST SLURRY WITH MAIZE GRAIN AND CASSAVA ROOT MEAL.

Brewers yeast slurry (BYS) was mixed with ground maize grain (GMG) at 1:1 and 1:1.5 ratios W/W and with cassava root meal (CRM) at 1:1 ratio w/w and were sun-dried to moisture contents of 10% or less within 48 hr. Two separate feeding trials were conducted to determine performance of weaner-grower pigs fed diets containing the BYS mixtures. In the first trial, 3 diets were formulated; the maize-based control (GMG 1), and those containing mixtures of GMG and BYS at 1.5:1 (MYS2) and 1:1 (MYS3) ratios w/w. Three-way crossbred weaner pigs of Large White, Landrace and Hampshire breeds averaging 11.78kg liveweight and approximately 8 wk old were allocated in groups of 4 and fed each of the 3 test diets in two replicates, for 35 days. Performance data showed that ADG, ADF, Feed conversion ratio and feed cost/kg liveweight gain (N) were 0.43, 0.42, 0.40 kg; 1.03, 0.95, 0.96 kg; 2.59, 2.35, 2.39 and 17.28, 14.78, 14.11 for CMG1, MYS2, MYS3, respectively. In the second 35-day feeding trial, approximately 14 wk old three-way crossbred pigs similar to the above, and averaging 25.60 kg liveweight were fed diets based on maize grain (MSB), cassava root meal alone (CRM), or CRM mixed with BYS (CYS). ADG, ADF, FCR ratio and feed cost/kg liveweight gain (N) for MSB, CRM, CYS were 0.58, 0.56, 0.66 kg; 1.63, 1.60, 1.71 kg; 2.84, 3.07, 2.62 and 16.68, 13.42, 9.46, respectively. The inclusion of BYS in diets reduced their cost and improved feed utilization with consequent reduced cost of weaner-grower pig liveweight gain.

Supplementation of brewer’s yeast slurry improves the performance of dairy cattle

Brewer's yeast slurry is the by-product of the beer processing industry which includes live cells of Saccharomyces cerevisiae. It is rich in high-quality protein, vitamins and minerals essential for the growth and well-being of animals. Moreover, Saccharomyces cerevisiae improves the growth of beneficial microflora in the rumen of ruminant animals. Sri Lanka is importing a large amount of milk and milk products to fulfill the demand of consumers. Lack of high-quality feed is one of the major concerns which hinders the dairy production in the country. Therefore, the purpose of this study was to investigate the effects of supplementing brewer's yeast slurry on the performance of dairy cattle in large scale production. In this study, 120 lactating cows were selected and divided into two groups as control and treatment considering their production, breed, and stage of lactation. The complete study period was 77 days. In the first period, the treatment group was fed with brewer's yeast slurry for 32 days. In the second period, which included 26 days both treatment and control groups were not fed brewer's yeast slurry. In the third period, the treatment group was fed brewer's yeast slurry for 19 days. Milk samples were collected daily and milk weight, fat content and density were measured. According to the results, milk production was significantly higher in the treatment group. Furthermore, supplementation of brewer's yeast slurry has improved the total solids and fat content of the milk.

Supplementation of brewer's yeast slurry improves the performance of dairy cattle

Supplementation of brewer's yeast slurry improves the performance of dairy cattle

Biochemical Implications of Biotransformation of Some Toxic Floras Using Natural Local Enzyme Sources.

Recently, it has been established that simultaneous saccharification and fermentation is a potent technique for the detoxification of harmful plant materials. Following encouraging simultaneous medicinal applications of snail slime and yeast, we exploited their hydrolytic and fermentation potentials to prevent toxicities of the selected floras; Erythrodontium barteri (EB), bracken fern (BF), and crustose lichens (CL). The applicability of the saccharification process has been described in a patent (WO2005010193A2). The plants were bioprocessed using snail digestive juice and yeast slurry and their health effects were evaluated. Seventy rats were divided equally into groups, treated with single doses of aqueous extracts of the plants and their bioprocessed forms, and compared with control rats. The plants showed very high antinutrients levels, which significantly reduced after SSF with enhanced flavonoids, alkaloids and phenols. Potential alterations of WBC differentials, RBC, liver and renal function markers indices were mitigated by bioprocessed extracts. MDA, SOD, GRase, XO and XDH levels in rats administered the bEB and CL were equivalent to the levels found for the control rats. Some bioprocessed plants produced unaltered insulin, ghrelin, and leptin levels. The bioprocessed extracts, when compared to the effects of unprocessed extracts, produced lower TNF-α, Caspase-3, and adiponectin levels and mitigated the potential suppression of Na+/K+-ATPase levels. Potential depletion of inhibin-B, testosterone, estrogen, and prolactin was mitigated after bioprocessing. This study, thus, validates the application of bioprocessing using snail digestive juice and yeast as an effective approach to reduce the potential toxicities of harmful plants.

Feed Efficiency and Blood Profiles of West African Dwarf Goats Fed Pleurotus tuber-regium Biodegraded Rice Straw and Maize Offal -Brewer Yeast Slurry Mixture

Feed Efficiency and Blood Profiles of West African Dwarf Goats Fed Pleurotus tuber-regium Biodegraded Rice Straw and Maize Offal -Brewer Yeast Slurry Mixture

Nutrient Digestibility, Carcass Yield and Production Economics of West African Dwarf Goats Fed Pleurotus Tuber-Regium Biodegraded Rice Straw and Maize Offal-Brewer Yeast Slurry Mixture

Nutrient Digestibility, Carcass Yield and Production Economics of West African Dwarf Goats Fed Pleurotus Tuber-Regium Biodegraded Rice Straw and Maize Offal-Brewer Yeast Slurry Mixture

The effects of different heating periods and exclusion of some fermentation conditions on bioethanol production from plantain pseudo-stem waste using the digestive juice of Archachatina marginata, garlic and Saccharomyces cerevisiae

ABSTRACTLignocellulosic biomass represents the largest renewable reservoir of potentially fermentable carbohydrates on earth, and its utilization for ethanol production continues to be a subject of worldwide interest. The present study evaluated the effect of 0, 30, 60 and 90 min heating periods on fermentation setups containing a mixture of 100 g plantain pseudo-stem waste, 250 ml of digestive juice of African land snail (Archachatina marginata), 4 g garlic and 200 ml of yeast slurry. On exclusion of some fermentation conditions, the yield of ethanol was evaluated for fermentation setups excluding yeast and garlic, yeast only, digestive juice of African land snail and garlic, digestive juice of African land snail only, and garlic. From the results, the best yield of ethanol at 76.0 ml ± 3.5 of distillate containing 21.7% ± 2.1 (w/v) ethanol composition was obtained at 60 min heating period, which declined continuously as the heating period increased to 90 min. No significant change (p ) in the ethanol yield was observed between the fermentation setups excluding the digestive juice of snail and garlic, and yeast only. The ethanol yield obtained from the fermentation setup excluding garlic alone was 79.7 ml ± 2.5 distillate containing 9.7% ± 1.5 ethanol by volume and the formation of acetic acid. This result suggests that the optimum heating period to enable the accessibility of cellulose degrading enzymes from the digestive juice of the African land snail is 60 min, and that constituents of garlic can promote the inhibition of acetic acid synthesis from fermentation.

Performance of West African Dwarf Goats Fed Pleurotus tuber-regium Biodegraded Rice Straw and Maize Offal: Brewer Yeast Slurry Mixture

Performance of West African Dwarf Goats Fed Pleurotus tuber-regium Biodegraded Rice Straw and Maize Offal: Brewer Yeast Slurry Mixture

Biosorption of anionic textile dyes from aqueous solution by yeast slurry from brewery

ABSTRACT This study investigated the biosorption of the anionic textile dyes: Reactive Red 239 (RR239), Reactive Black B (RBB) and Direct Blue 85 (DB85) according to pH, biomass dosage, contact time and dye concentration onto waste beer yeast slurry. The kinetics and isotherm of the removal of dyes were also studied. The equilibrium of biosorption reaction was reached after 30 min for the reactive dyes and after 60 min for the direct dye. Optimum decolorization was observed at pH 2 and 0.63 g/L of biomass dosage. The kinetic data of the three dyes were better described by the pseudo second-order model. The adsorption process followed the Langmuir isotherm model and the biosorption capacity being estimated to be 152.9, 162.7 and 139.2 mg/g for RR239, RBB and DB85, respectively. Our findings indicated that the waste beer yeast slurry was an attractive low-cost biosorbent for the removal of anionic textile dyes from aqueous solution.

Impact of changes in fermentation time, volume of yeast, and mass of plantain pseudo-stem substrate on the simultaneous saccharification and fermentation potentials of African land snail digestive juice and yeast.

This study was carried out to investigate the effect of variations in mass of plantain pseudo-stem waste, volume of yeast used, and fermentation time on the product yield resulting from simultaneous saccharification and fermentation using digestive juice of African land snail and yeast. The experiment was divided into three stages which included a total of fifty seven (57) experimental setups containing sixteen (19) different combinations of the varied substrates. The results show that by varying the mass of plantain pseudo-stem waste, the production of ethanol was optimized at a mass of 250 g, which yielded 125.6 ml ± 3.5 of distillate and a percentage ethanol composition of 25.0 ± 3.6. While varying the volume of yeast used between 50 and 250 ml, with 250 g of plantain pseudo-stem waste, 250 ml of snail digestive juice and 4 g garlic for 24 h, acetic acid was detected in the setup containing 200 ml of yeast, but was not detected in similar experimental setups containing 6 g garlic. The optimum ethanol production while varying the volume of yeast slurry was recorded to be 182.3 ml ± 4.9 of distillate with 28.0% ± 1.0 ethanol composition. Variations in fermentation periods had the greatest impact on the percentage composition of ethanol and the volume of ethanol produced showing the best fermentation period for obtaining optimal ethanol production to be at 96 h. These findings show that the best specifications for the optimum production of ethanol from a 250 g of plantain pseudo-stem waste using 250 ml snail digestive, are 200 ml of yeast slurry, 6 g of garlic to ferment for a period of 96 h.

Evaluation of sulfur isotopic enrichment of urine metabolites for the differentiation of healthy and prostate cancer mice after the administration of 34S labelled yeast

Sulfur isotopic enrichment of urine metabolites in healthy and prostate cancer mice using 34S enriched yeast and High Performance Liquid Chromatography coupled to Multicollector Inductively Coupled Plasma Mass Spectrometry (HPLC-MC-ICP-MS) has been evaluated. A 30 weeks experiment (since the eleventh to the fortieth week of life) was carried out collecting the urine of three healthy mice and three transgenic mice with prostate cancer during 24h after a single oral administration of a 34S enriched yeast slurry. The isotopic enrichment of different sulphur metabolites was monitored by coupling a C18 reverse phase HPLC column with a multicollector ICP-MS using a membrane desolvating system. Quantification of sulfur in the chromatographic peaks was carried out by post-column isotope dilution using a 33S enriched spike. Differences between the 34S enrichment in the urine metabolites of healthy and prostate cancer mice were found from the beginning of the disease. Both populations could be differentiated using a principal component analysis (PCA). Finally, 7 unknown mice were correctly classified in each population using a linear discriminant analysis.

A Semi-Empirical Approach to Estimate Kinetic Parameters for the Batch and Continuous Settling of Flocculating Yeast Slurries

The knowledge of sedimentation kinetics is a necessary requisite for an adequate design of settlers aiming the separation and recovery of yeasts in alcoholic fermentation processes. In this study, batch and continuous settling tests were performed using slurries of flocculating yeasts obtained from the fermentation of sugarcane juice in a tower reactor with cell recycling. The batch tests were conducted in a 250 mL cylindrical glass vessel with initial concentrations of yeast between 90 and 100 g/L by measuring the variation over time of the height of the interface between the clarified liquid and the thickened slurry. These data were conveniently converted into cell concentration of the thickened sludge and a semi-empirical equation was developed to estimate the kinetic parameters of the settling. Data taken in a continuous settler in two continuous fermentation systems of different scales with cell recycle were also well fitted by the semi-empirical equation, but the adjusted parameters were different from those obtained for the batch tests.

Part I: the influence of serial repitching ofSaccharomyces pastorianuson the uptake dynamics of metal ions and fermentable carbohydrates during the fermentation of barley and gluten-free buckwheat and quinoa wort

Recently, research has been focusing on the use of alternative raw materials for brewing purposes and gluten-free beer-like beverages from malted buckwheat and quinoa are of commercial interest. A common commercial process involves the serial repitching of the yeast biomass, but this has not been described using buckwheat and quinoa wort fermentations. Our research studies (Parts I–III) explored the serial repitching of the yeast strain Saccharomyces pastorianus TUM 34/70 on the composition of a barley, buckwheat and quinoa fermentation medium. The present paper focuses on the fermentation performance and the uptake dynamics of metal ions and fermentable carbohydrates. Both pseudocereals showed high variations in all of the attributes examined during successive fermentations. In buckwheat the differences between successive fermentations were similar to those observed with barley, whereas differences in quinoa varied quite significantly from those observed with barley and showed a directional trend, suggesting a general weakening of the yeast from the sixth successive fermentation onward. In particular, the assimilation of the fermentable carbohydrates lessened and metal ion uptake appeared poorly controlled. It was concluded that buckwheat showed good potential for serial repitching of S. pastorianus TUM 34/70, whereas serial repitching of a quinoa wort appeared to be limited to five or six fermentations. Copyright © 2015 The Institute of Brewing & Distilling

Characterization of Hop Acids in Spent Brewer's Yeast from Craft and Multinational Sources

Spent brewer's yeast, a significant byproduct of brewing, presents a disposal issue for craft breweries. To understand value-added opportunities for its use, we measured hop acid profiles of spent yeast from three beer styles produced by a craft brewery and spent yeast from three multinational breweries using high-performance liquid chromatography with photodiode array detection/mass spectrometry. The average α-acid content of craft yeast (2,074 ± 531 μg/g) was 12-fold higher than multinational brewery samples (167 ± 89 μg/g), and the average total hop acid content of craft yeast samples (2,557 ± 622 μg/g) was fivefold higher than the multinational brewery yeast samples (487 ± 136 μg/g). Centrifuged craft yeast slurry from both light and dark ales had 7-to 10-fold, 150- to 158-fold, and >200-fold higher content of iso-α-, α-, and ß-acids, respectively, than that in the corresponding beer, demonstrating a high affinity of brewer's yeast for hop acids. Ongoing research has shown that hop acids have antioxidant, anti-inflammatory, anticancer, and antibacterial activities. The elevated content found in spent craft brewer's yeast suggests consideration for use as a high-value functional food ingredient.