Brewer's Yeast Research Articles

Antipyretic activity of the hydro-alcoholic extract of Artemisia absinthium L. as a standalone and as an adjuvant with barley water against yeast-induced pyrexia in albino Wistar rats.

In Unani medicine, a comprehensive treatment plan has been delineated to deal with febrile illnesses using herbal drugs along with modified dietetics, which stands as apromising area of research. The present study was aimed atevaluating the antipyretic activity of the HAE of Artemisia absinthium L. whole plant as a standalone and as an adjuvant with barley water in an animal model of pyrexia tovalidate the age-old Unani principle of the treatment. The pyrexia was induced in all the groups except the plain control using Brewer's yeast. Group II did not receive any treatment, while group III received crocin, group IV received HAE of A.absinthium, group V administered Maal-Sha'ir, and group VI was treated with the HAE of A.absinthium along with Ma al-Sha'ir by oral route. The rectal temperature of each rat was recorded at '0' h, 30 min, 60 min, and 180 min. The mean rectal temperature of group III went down from 101.82±0.20 °F to 100.4±0.57 °F over the period of(0-180) minutes, whereas the mean temperature in groupIV went down from 102.45±0.60 °F to 100.14±0.57 °F. The mean rectal temperature of group V decreased from 100.62±0.11 °F to 99.55±0.51 °F, while the mean rectal temperature of group VI went down from 101.95±0.1 °F to97.7±0.11 °F. It is concluded that the HAE of A.absinthium L. as a standalone and along with Ma al Sha'ir showed excellent antipyretic activity as compared to the standard drug in an animal model.

Effect of different levels of brewer's yeast Schizosaccharomyces pombe and molasses on some cellular Blood parameters traits of common carp Cyprinus carpio L.

Study was done at Agricultural Research Experiment Station in Um Akf in Samawa, from 1 October/2022 to 20 December /2023, at a dugout pond, it is about 570 meters away from the Euphrates/Atshan River, at coordinates E 45.189309N ,31.321394, to determine the effect of different levels of Brewer's yeast Schizosaccharomyces pombe and molasses and their mixture on fish blood. Experimental parameters were as follows: T0: control diet (without additives). T1: add 0.5 mg brewer's yeast / kg diet. T2: add 1 mg brewer's yeast / kg diet. T3: add 1.5 mg molasses / kg diet. T4: add 2 mg molasses / kg diet. T5: add 0.5 mg brewer's yeast + 1.5 mg molasses / kg diet. T6: add 0.5 mg brewer's yeast + 2 mg molasses / kg diet. T7: add 1 mg brewer's yeast + 1.5 mg molasses / kg diet. T8: add 1 mg brewer's yeast + 2 mg molasses / kg diet. Results indicated that all special treatments, in addition to brewer's yeast and molasses, significantly improved cell blood parameters RBC, Hb, PCV, MCV, MCHC and Platelets) of carp fish compared to control treatment, T2 treatment (addition of 1.5 mg molasses / kg diet) gave the best results significantly compared to the rest of the experimental treatments.

SAGA Complex Subunit Hfi1 Is Important in the Stress Response and Pathogenesis of Cryptococcus neoformans.

The Spt-Ada-Gcn Acetyltransferase (SAGA) complex is a highly conserved co-activator found across eukaryotes. It is composed of a number of modules which can vary between species, but all contain the core module. Hfi1 (known as TADA1 in Homo sapiens) is one of the proteins that forms the core module, and has been shown to play an important role in maintaining complex structural integrity in both brewer's yeast and humans. In this study we successfully identified the gene encoding this protein in the important fungal pathogen, Cryptococcus neoformans, and named it HFI1. The hfi1Δ mutant is highly pleiotropic in vitro, influencing phenotypes, ranging from temperature sensitivity and melanin production to caffeine resistance and titan cell morphogenesis. In the absence of Hfi1, the transcription of several other SAGA genes is impacted, as is the acetylation and deubiquination of several histone residues. Importantly, loss of the gene significantly impacts virulence in a murine inhalation model of cryptococcosis. In summary, we have established that Hfi1 modulates multiple pathways that directly affect virulence and survival in C. neoformans, and provided deeper insight into the importance of the non-enzymatic components of the SAGA complex.

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 β-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 β-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 β-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 β-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.

Food by-product valorisation in nutrients through spent brewer's yeast bioprocessing with Propionibacterium freudenreichii

This study investigated the potential of Propionibacterium freudenreichii to enhance the nutritional quality of spent brewer's yeast (SBY) by producing short-chain fatty acids (SCFAs) and vitamin B12 (B12). SBY was also evaluated as a growth medium for P. freudenreichii. Four SBY samples from different breweries were utilized and compared to microbiological yeast extract (YE). The tested SBY samples exhibited similar chemical compositions in terms of protein content, free amino acids (FAAs), SCFAs, carbohydrates, riboflavin, and cobalt, whereas YE was richer in most of these substances. However, P. freudenreichii growth was hindered by polyphenols in SBY, as evidenced by better growth in samples with lower polyphenol levels and the control sample (YE). SCFA synthesis was efficient in the SBY sample, resulting in 1.3 mg mL−1 of acetic acid and 1.70 mg mL−1 of propionic acid. Furthermore, P. freudenreichii fermentation increased essential free amino acids (FAAs) in all tested samples. SBY was found to be a suitable medium for supporting the production of the active form of B12, with a concentration of 25.2 ng mL−1. However, YE outperformed SBY as a medium for B12 synthesis, yielding a concentration of 214.3 ng mL−1 after fermentation. The results indicate that both SBY and YE can serve as one-component sustainable growth media, valorised with valuable compounds through P. freudenreichii fermentation. In conclusion, SBY offers a novel opportunity for the biotechnological synthesis of SCFAs, FAAs, and B12 through P. freudenreichii fermentation.

Biological recovery of phosphorus (BioP-Rec) from wastewater streams using brewer's yeast on pilot-scale.

Most recent advances for phosphorus (P) recovery using brewery yeast on laboratory scale were used to scale up to a pilot-scale process (BioP-Rec module) and applied in a full-scale wastewater treatment plant (WWTP). A P balance was established for WWTP Markranstädt according to two thresholds: (1) the economic feasibility threshold for P recovery of 0.05kg/m3 of free P, and (2) the German Sewage Sludge Ordinance (GSSO) threshold, which demands that all WWTPs with a P content in dry matter (DM) of biosolids of 20 gP/kgDM or higher in the coming years must perform mandatory P recovery. In terms of defined thresholds, return and excess sludges were identified as the most feasible WWTP process streams for P recovery. In a 1 m3 BioP-Rec module a 3 stage process was established. From the P-rich water-phase of the return sludge produced in stage 1, which contained 0.051kg/m3 of free P, 77.56% was taken up by P-depleted brewer's yeast Saccharomyces pastorianus in 3h in stage 2. In stage 3, the yeast was concentrated in 1h to produce yeast sludge as a fertilizer product. We demonstrated a novel pilot-scale process for the production of bio-based P-rich fertilizer.

Glycation-induced enhancement of yeast cell protein for improved stability and curcumin delivery in Pickering high internal phase emulsions

Pickering high internal phase emulsions (HIPEs) have gained significant attention for various applications within the food industry. Yeast cell protein (YCP), derived from spent brewer's yeast, stands out as a preferred stabilizing agent due to its cost-effectiveness, abundance, and safety profile. However, challenges persist in utilizing YCP, notably its instability under high salt concentration, thermal processing, and proximity to its isoelectric point. This study aimed to enhance YCP's emulsifying properties through glycation with glucose and evaluate its efficacy as a stabilizer for curcumin (CUR)-loaded HIPEs. The results revealed that glycation increased YCP's surface hydrophobicity, exposing hydrophobic groups. This augmentation, along with steric hindrance from grafted glucose molecules, improved emulsifying properties, resulting in a thicker interfacial layer around oil droplets. This fortified interfacial layer, in synergy with steric hindrance, bolstered resistance to pH changes, salt ions, and thermal degradation. Moreover, HIPEs stabilized with glycated YCP exhibited reduced oxidation rates and improved CUR protection. In vitro digestion studies demonstrated enhanced CUR bioaccessibility, attributed to a faster release of fatty acids. This study underscores the efficacy of glycation as a strategic approach to augment the applicability of biomass proteins, exemplified by glycated YCP, in formulating stable and functional HIPEs for diverse food applications.

Sustainable bio-manufacturing of D-arabitol through combinatorial engineering of Zygosaccharomyces rouxii, bioprocess optimization and downstream separation

Biosynthesis of D-arabitol, a high value-added platform chemical, from renewable carbon sources provides a sustainable and eco-friendly alternative to the chemical industry. Here, a robust brewing yeast, Zygosaccharomyces rouxii, capable of naturally producing D-arabitol was rewired through genome sequencing-based metabolic engineering. The recombinant Z. rouxii obtained by reinforcing the native D-xylulose pathway, improving reductive power of the rate-limiting step, and inhibiting the shunt pathway, produced 73.61% higher D-arabitol than the parent strain. Subsequently, optimization of the fermentation medium composition for the engineered strain provided 137.36 g/L D-arabitol, with a productivity of 0.64 g/L/h in a fed-batch experiment. Finally, the downstream separation of D-arabitol from the complex fermentation broth using an ethanol precipitation method provided a purity of 96.53%. This study highlights the importance of D-xylulose pathway modification in D-arabitol biosynthesis, and pave a complete and efficient way for the sustainable manufacturing of this value-added compound from biosynthesis to preparation.

Chromatin regulator Eaf3p regulates nitrogen metabolism in Saccharomyces cerevisiae as a trans-acting factor.

In this study, the mechanism of chromatin regulator Eaf3p regulating nitrogen metabolism in S. cerevisiae was investigated. It provides theoretical support for epigenetic modifications of cells to alter the level of histone modifications, coordinate the expression of multiple genes, and make it more conducive to the co-metabolism of multiple nitrogen sources. Moreover, it provides new ideas for industrial brewing yeast strains to achieve nitrogen source metabolism balance, reduce the accumulation of harmful nitrogen metabolites, and improve fermentation efficiency. This study provides a reference for changing the performance of microbial strains and improving the quality of traditional fermentation products and provides a theoretical basis for studying epigenetic modification and nitrogen metabolism regulation. It has an important theoretical explanation and practical application value. In addition, this study also provides useful clues for the study.

Pasta fortified with β-glucan Isolated from brewer’s yeast (Saccharomyces cerevisiae) by-product

β-glucan from brewer's spent yeast is a novel ingredient approved to be included in the human diet. This paper evaluated the effects of β-glucan extracted from spent brewer's yeast on the physico-chemical, rheological, textural, microstructure, and molecular characteristics of common and durum wheat pasta, at different addition levels. The results showed a decrease in dough viscous and elastic moduli, while the resistance to deformation and hardness raised as the addition level increased. Pasta quality parameters were influenced by the β-glucan content depending on the wheat type, with lower pasta firmness (2.76 and 3.40 N for common and durum controls vs. 2.76–1.97 and 3.35–2.73 N for common and durum enriched pasta respectively), increased carbohydrate content (from 85.63% to 85.91–86.95% in common wheat pasta, and from 81.89 to 82.12–82.28% in durum pasta), cooking loss (from 4.73% in common control to 4.91% for 4% common wheat-β-glucan pasta, and from 3.68 in durum control to 5.05% for 4% durum wheat-β-glucan), and darker color being obtained. Pasta microstructure and molecular FT-IR characteristics confirmed the presence of β-glucan in cooked pasta and depicted protein denaturation and contribution to the final product matrix. These results represent new insights into the development of convenient matrices for functional ingredient incorporation.

Genome-scale metabolic models reveal determinants of phenotypic differences in non-Saccharomyces yeasts

BackgroundUse of alternative non-Saccharomyces yeasts in wine and beer brewing has gained more attention the recent years. This is both due to the desire to obtain a wider variety of flavours in the product and to reduce the final alcohol content. Given the metabolic differences between the yeast species, we wanted to account for some of the differences by using in silico models. Results We created and studied genome-scale metabolic models of five different non-Saccharomyces species using an automated processes. These were: Metschnikowia pulcherrima, Lachancea thermotolerans, Hanseniaspora osmophila, Torulaspora delbrueckii and Kluyveromyces lactis. Using the models, we predicted that M. pulcherrima, when compared to the other species, conducts more respiration and thus produces less fermentation products, a finding which agrees with experimental data. Complex I of the electron transport chain was to be present in M. pulcherrima, but absent in the others. The predicted importance of Complex I was diminished when we incorporated constraints on the amount of enzymatic protein, as this shifts the metabolism towards fermentation.Conclusions Our results suggest that Complex I in the electron transport chain is a key differentiator between Metschnikowia pulcherrima and the other yeasts considered. Yet, more annotations and experimental data have the potential to improve model quality in order to increase fidelity and confidence in these results. Further experiments should be conducted to confirm the in vivo effect of Complex I in M. pulcherrima and its respiratory metabolism.

The effect of mixed culture fermentation of Saccharomyces cerevisiae and Saccharomyces cerevisiae var. diastaticus on fermentation parameters and flavor profile.

Belgian Saisons and Lambics are two well-known examples in the brewing industry of mixed fermentations, combination of two or more yeast and/or bacteria strains. The purpose of this study was to determine the impact different pitch rates of Saccharomyces cerevisiae (traditional brewing yeast) and S. cerevisiae var. diastaticus (a variant associated with Belgian styles) had on the fermentation kinetics and concentration of the volatile compounds in the finished beers. A series of brews were performed utilizing ratios of S. cerevisiae and diastaticus. The fermentations were heavily monitored, and a model was used to fit fermentation variables. It was found that mixed fermentations produced behaviors that were predictable and proportional to the mixture ratios. As expected, the pure cultural fermentations of diastaticus had a slower fermentation midpoint (M) at 45.45h versus 28.28h for S. cerevisiae with the mixed ones falling in between the two. Flavor and aroma play a key role in the acceptability of beer. The mixed fermentations showed a combination of the two different yeast strains aromatic profiles. When combined, there was a strong linearity between alcohols (R2 =0.94), esters (R2 =0.89), and the overall total (R2 =0.91) volatile compounds. PRACTICAL APPLICATION: Modeling is a widely utilized tool in several different fields. The purpose of this research is to apply modeling techniques to describe the fermentation speed and flavor profile of a mixed fermentation between S. cerevisiae and diastaticus. The equations from this data can be used by brewers for product development purposes to make beers with certain flavor profiles within a desired timeframe.

Nutritional Potential of Spent Brewer's Yeast, A Residual By-Product of Beer Production in Breweries for Future Applications

The recovery of by-products from food processing chains represents an area of interest in the current world. Waste from beer production, such as beer lees or spent brewer's yeast, constitutes between 1.5 and 3 kg/100 L of beer, representing a source of pollution but a by-product available in quantity. This study aims to characterize the beer lees from breweries and propose possible ways of recovery. The scientific methods have been applied to highlight the nutritional potential of this by-product. Spent brewer's yeast is a high-biological value protein source (46.77%) with a well-balanced amino acid profile. Amino acids (glutamic acid and aspartic acid) and the essential amino acids leucine, lysine and valine are the most abundant, while sulfur amino acids, such as methionine and cysteine, are the least abundant. With a high mineral content (7.3%), the spent brewer's yeast contains significant amounts of manganese 5.54x10-2 mg/k, sodium 3.92x10-2 mg/k, and potassium 3.59x10-2 mg /k. The B complex vitamins are present in large quantities, followed by vitamins C, A and D. Less than 3% of the composition of the spent brewer's yeast is made up of lipids. The most abundant of fatty acids determined for the saturated category is palmitic acid, while oleic acid represents monounsaturated fatty acids, and polyunsaturated fatty acids are represented by linoleic acid and linolenic acid. Carbohydrates (32.77 %) are also important constituents of the dry matter of this by-product. This study showed that spent beer yeast is a source of polyphenol. Spent brewer's yeast has advantages for being incorporated into animal nutrition to meet nutritional needs. Further studies could lead to the production of activated carbon and hydrogen as excellent sources of alternative energy.

Fluctuating selection facilitates the discovery of broadly effective but difficult to reach adaptive outcomes in yeast.

Evolutionary compromises are thought to be common under fluctuating selection because the mutations that best enable adaptation to one environmental context can often be detrimental to others. Yet, prior experimental work has shown that generalists can sometimes perform as well as specialists in their own environments. Here we use a highly replicated evolutionary experiment (N = 448 asexual lineages of the brewer's yeast) to show that even though fluctuation between two environmental conditions often induces evolutionary compromises (at least early on), it can also help reveal difficult to reach adaptive outcomes that ultimately improve performance in both environments. Specifically, we begin by showing that yeast adaptation to chemical stress can involve fitness trade-offs with stress-free environments and that, accordingly, lineages that are repeatedly exposed to occasional stress tend to respond by trading performance for breadth of adaptation. We then show that on rare occasions, fluctuating selection leads to the evolution of no-cost generalists that can even outcompete constant selection specialists in their own environments. We propose that the discovery of these broader and more effective adaptive outcomes under fluctuating selection could be partially facilitated by changes in the adaptive landscape that result from having to deal with fitness trade-offs across different environmental conditions. Overall, our findings indicate that reconciling the short- and long-term evolutionary consequences of fluctuating selection could significantly improve our understanding of the evolution of specialization and generalism.

PSVIII-13 Evaluating the Effects of a Dried brewer’s Yeast Product on the Fecal Characteristics, Metabolites, and Microbiota Populations of Adult Dogs

Abstract Inclusion of brewer’s yeast in pet foods has become popular because of the potential health benefits it provides. However, more research is needed to evaluate the effects of different brewer’s yeast products on canine gut health outcomes. This study aimed to investigate the effects of a brewer’s yeast product on the fecal characteristics, metabolites, and microbiota populations of adult dogs. Sixteen healthy adult dogs (BW: 9.0 ± 1.7 kg) were acclimated for 7 days and then randomly assigned to a control diet containing no yeast or a brewer’s yeast-containing diet (n = 8/group) for a 21-day period. Fresh fecal samples were collected before and after treatment for measurement of fecal scores, pH, dry matter content, metabolite concentrations [short-chain fatty acids (SCFA), branched-chain fatty acids (BCFA), ammonia, phenols, indoles], and microbiota populations. All data were analyzed as a percent change from baseline using the PROC MIXED procedure of SAS, with treatment as the main effect and dog as a random effect. Significance was declared at P ≤ 0.05, and trends reported if 0.05 < P ≤ 0.10. The brewer’s yeast treatment tended to increase (P = 0.10) fecal butyrate concentrations more than that of controls, but fecal characteristics (pH; dry matter; fecal scores) and other metabolite concentrations were not affected by treatment. Fecal bacterial alpha diversity metrics were not affected by treatment, but beta diversity analysis (unweighted UniFrac distances) tended (P = 0.09) to show a shift between treatments. Change in relative abundance of fecal Blautia was less (P = 0.05) in dogs fed brewer’s yeast than controls, but other bacterial genera were unaffected by diet. In conclusion, this study suggests that the dried brewer's yeast products tested had little impact on fecal characteristics, metabolites, or microbiota populations of adult dogs. The tendency of greater fecal butyrate concentrations in dogs fed brewer’s yeast is encouraging, but further research is needed to identify the potential health benefits of these products in canine diets.

PSIX-15 The Effects of Torula Yeast as a Protein Source on Digestibility, Inflammation, and Gut Microbiome in Labrador Retrievers with Chronically Poor Stool Quality

Abstract Four Rivers Kennel examined the effects of varying protein sources on digestibility, inflammation, and gut microbiota in Labrador Retrievers with historically poor stool quality. Thirty dogs (n = 15 males and n= 15 females; ages 3 to 10 years) with stool quality scores ≤ 2.5 on a 5 point scale were randomly assigned to 1 of 3 diets meeting AAFCO requirements with differing protein sources and similar nutrient profiles: 1) chicken meal (PC); 2) 10% brewer’s yeast (BY); and 3) 10% torula yeast (TY; SylPro, Arbiom, Durham, NC). Another 10 dogs (n = 5 males and n = 5 females) with normal stool quality (score ≥ 3) received diet 1 and served as negative control (NC). After 7 days acclimation to diet 1, dogs began treatments. Daily stool scores and weekly body weights were recorded. On days 7, 21, and 36, blood serum was analyzed for C-reactive protein (CRP), and feces for S100A12, alpha-1 proteinase inhibitor (a1PI), calprotectin, and microbiota dysbiosis index (MDI). Apparent total tract digestibility was assessed using the indicator method with 2 g titanium dioxide administered orally via gel capsules. Statistical analysis was performed by repeated measures model in SAS for stool scores, body weight, biomarkers, and microbiota or by one-way ANOVA in JMP for digestibility coefficients. Stool scores were greater in NC (P < 0.01), changed daily in all groups (P < 0.01) without noticeable overall trends, and were not affected by treatment*day interaction (P = 0.64). Body weight was greater (P = 0.01) and CRP less (P < 0.01) in NC dogs than poor stool dogs. Dry matter and carbohydrate digestibility did not differ between groups (P ≥ 0.14). NC dogs had greater fat digestibility compared with BY dogs (94.64 ± 1.33 % vs 91.65 ± 1.25%; P = 0.02). Protein digestibility was reduced in PC (58.91 ± 4.68%) and BY (58.26 ± 4.42%) compared with NC (75.52 ± 5.01 %), but TY diet improved protein digestibility to levels similar to NC (72.18 ± 5.01%, P = 0.03). There were no treatment effects on S100A12 or a1PI (P ≥ 0.44). Calprotectin decreased at a greater rate overtime in TY dogs (P < 0.01). There was a treatment*day interaction for MDI; BY and TY fluctuated less overtime (P = 0.01). Blautia (P = 0.03) and Clostridium hiranonis (P = 0.05) abundances were reduced in BY and TY. Dogs never exhibited significant dysbiosis (MDI < 2), and bacterial abundances remained within normal ranges. Dogs with chronically poor stool quality experience reduced body weights, increased serum CRP, and altered nutrient digestibility, but TY helped improve protein and fat digestibility, sustain microbiome, and reduce fecal calprotectin. Feeding torula yeast long-term may help improve plane of nutrition to better maintain weight and reduce inflammation in dogs with chronically poor stool quality.

Valorization of spent Brewers yeast in the integrated production of the fungal exopolysaccharide (1 → 6)-β-D-glucan (lasiodiplodan) and single-cell protein

Spent Brewers yeast was studied as a low-cost alternative feedstock for sustainably producing a high value-added microbial β-D-glucan (lasiodiplodan). The potential of using the mycelial biomass (single-cell protein, SCP) generated in the production of β-glucan was also evaluated as a strategy of an integrated biorefining. Five cell lysis protocols were studied to obtain a yeast cell lysate rich in nutrients. Mineral supplementation of the fermentation medium was assessed, and the SCP produced was characterized by the nutritional composition, amino acid, and lipid profiles. Lasiodiplodia theobromae MMPI was effective in the co-production of lasiodiplodan ((1 → 6)-β-D-glucan)) and SCP in a cell lyzate-based medium. Enzymatic lysis with Alcalase promoted more significant cell rupture and release of soluble intracellular components. Highest production of lasiodiplodan (2.12 gL-1) and mycelial biomass (9.95 gL-1) resulted from Alcalase-treated cell lysate-based medium (7 gproteinL−1) supplemented with sucrose (60 gL-1). Under these conditions, volumetric productivities of lasiodiplodan and mycelial biomass: 0.029 gL−1h−1 and 0.138 gL−1h−1, respectively, were obtained. Mycelial biomass generated in this cultivation was rich in protein and contained all essential amino acids, especially high concentrations of leucine (69 mgg−1protein), lysine (62.2 mgg−1protein), valine (44.2 mgg−1protein), threonine (43.2 mgg−1protein). Co-production of lasiodiplodan and SCP could be an economically promising bioprospecting alternative.

Optimization of Brewer's Yeast Quantity in Liquid and Gel Larval Diets for the Mediterranean Fruit Fly.

Several artificial larval diets have been developed, evaluated and used for mass-rearing of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Teprhitidae). There are several efforts to reduce the cost of rearing and optimize the quality of the produced sterile males that are destined for release in sterile insect release programs. Survival, growth, longevity and reproductive capacity of sterile males are strongly connected with the most expensive ingredient, the brewer's yeast (protein), in the larval diet. The current study focused on settling the optimal content of brewer's yeast in a liquid diet and a gel diet. Egg hatch rates, developmental duration of immatures, pupation rate, pupae and adult survival were recorded as indicators of quantity and quality of the produced adults. Egg hatch was higher and larval developmental duration longer in the gel diet. In contrast to the liquid diet, an increase in brewer's yeast concentration was correlated with increased pupation rate and pupae survival in the gel diet. Reducing brewer's yeast up to 50% of its initial quantity had no significant effect on the survival of the emerging adults regardless of the diet type. Our findings may contribute to the production of low-cost and effective diets for use in mass-rearing facilities of medflies.

Complete recycling of Printed Circuit Boards: From base metal bioleaching in a semi-continuous reactor with dual regulation to gold biosorption with brewer's yeast

Bioleaching is a promising technology for recovering base metals and concentrating precious elements in secondary resources. In this study, the extraction of base metals from printed circuit boards (PCBs) was optimized using a dual control system including biomass encapsulation. Gold recovery was achieved in a second step by chemical dissolution followed by biosorption on brewer's yeast. A dual regulation system, controlling oxidoreduction potential (ORP) and copper concentration, was established. This system comprised two reactors interconnected in a loop: a leaching reactor and a biological reactor. Acidophilic bacteria in the biological reactor recycled ferrous into ferric iron in a low shear stress environment. The Fe3+ solution from the biological reactor recirculated to the leaching compartment (hosting the PCBs) based on ORP regulation (optimal setpoint: +410 mV vs Ag/AgCl). A second control aimed to maintain the copper concentration below the inhibitory level (15 g Cu2+ L−1) by addition of fresh medium and overflow of leachate. This configuration ensured the highest pulp density, operating consistently, in steady state, at the inhibitory concentration limit, the PCBs being added batch-wise when the stock within the leaching compartment was exhausted. Compared to planktonic cells, the encapsulated mode showed optimal base metals leaching yields: 100% for Cu, 24% for Al, 49% for Ni, and 100% for Zn, with a hydraulic retention time (HRT) of 92 h and an iron oxidation rate of 0.455 mg L−1 h−1. The reactor's productivity was 5.91 g Cu L−1d−1, corresponding to the leaching of 20.88 g PCBs L−1d−1. The gold enriched PCBs (from 290 to 450 mg Au kg−1) were then extracted using Aqua regia, with a 24:1 liquid/solid ratio at 80 °C for 2 h. Subsequent biosorption on brewer's yeast (10 g yeast L−1) selectively recovered gold, with 98% efficiency. Biosorption yields for “fresh” yeast resulting from a model brewing (90.8%) and commercial “active dry” yeast (88.7%) were comparable, indicating the potential use of spent yeast from brewing.

Carbon and nitrogen sources consumption by ale and lager yeast strains: a comparative study during fermentation.

The rapid and efficient consumption of carbon and nitrogen sources by brewer's yeast is critical for the fermentation process in the brewing industry. The comparison of the growth characterizations of typical ale and lager yeast, as well as their consumption preference to carbon and nitrogen sources were investigated in this study. Results showed that the ale strain grew faster and had a more extended stationary phase than the lager strain. However, the lager strain was more tolerant to the stressful environment in the later stage of fermentation. Meanwhile, the ale and lager yeast strains possessed varying preferences for metabolizing the specific fermentable sugar or free amino acid involved in the wort medium. The lager strain had a strong capacity to synthesize the extracellular invertase required for hydrolyzing sucrose as well as a strong capability to metabolize glucose and fructose. Furthermore, the lager strain had an advantage in consuming Lys, Arg, Val, and Phe, whereas the ale strain had a higher assimilation rate in consuming Tyr. These findings provide valuable insights into selecting the appropriate brewer's yeast strain based on the wort components for the industrial fermentation process. KEY POINTS: • The lager strain is more tolerant to the stressful environment. • The lager strain has the great capability to synthesize the extracellular invertase. • The assimilation efficiency of free amino acid varies between ale and lager.