Brewer's Yeast Research Articles

Cultivation of Flammulina velutipesmushroom using various agro-residues as a fruiting substrate

The objective of this work was to evaluate the feasibility of different agro-residues as a carbon source in the fruiting substrates of Flammulina velutipesmushroom and the effect of supplementation with the nitrogen sources spent brewer's yeast and rice bran. The following fruiting substrates were evaluated: rubber wood sawdust (SD), paddy straw (PS), palm empty fruit bunches (EFB), and palm-pressed fiber (PPF). Cultivation was done on each agro-residue, based on formulations consisting of two substrates at the ratios of 3:1, 1:1, and 1:3. Mycelial growth rate and basidiocarp yield were evaluated. The best fruiting substrates were PS+EFB (25:75), PS+PPF (50:50), and PPF (100), with biological efficiency of 185.09±36.98, 150.89±50.35, and 129.06±14.51%, respectively. No significant effects of supplementation with rice bran and spent yeast were observed on mycelial growth rate and biological efficiency. The cultivation of F. velutipes on oil palm wastes does not require additional nitrogen sources.

Effects of soy protein hydrolysates on the growth and fermentation performances of brewer's yeast

SummarySoy protein isolate was hydrolysed with Alcalase, Papain, Flavorzyme and Protemax, respectively, and further fractioned by ultrafiltration. The resulting soy protein hydrolysates (SPH) and their ultrafiltration fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast. Results showed that degree of hydrolysis, molecular weight distribution and amino acid composition of SPH significantly affected the growth, viability and fermentation performance of brewer's yeast. The SPH prepared from different proteolytic enzymes exhibited distinct growth‐ and fermentation‐promoting activity for brewer's yeast. The SPH treated with Protemax for 9 h and with the molecular weight below 3 kDa showed the highest growth‐promoting activity and induced more rapidly reducing sugar consumption and higher ethanol production. The relatively lower molecular weight and the hydrophilic and electropositive amino acid residues (Lys, His, Arg and Ile) in SPH might be responsible for its functionality, promoting the growth and fermentation of brewer's yeast.

Absence of fks1p in lager brewing yeast results in aberrant cell wall composition and improved beer flavor stability

The flavor stability during storage is very important to the freshness and shelf life of beer. However, beer fermented with a yeast strain which is prone to autolyze will significantly affect the flavor of product. In this study, the gene encoding β-1,3-glucan synthetase catalytic subunit (fks1) of the lager yeast was destroyed via self-clone strategy. β-1,3-glucan is the principle cell wall component, so fks1 disruption caused a decrease in β-1,3-glucan level and increase in chitin level in cell wall, resulting in the increased cell wall thickness. Comparing with wild-type strain, the mutant strain had 39.9 and 63.41% less leakage of octanoic acid and decanoic acid which would significantly affect the flavor of beer during storage. Moreover, the results of European Brewery Convention tube fermentation test showed that the genetic manipulation to the industrial brewing yeast helped with the anti-staling ability, rather than affecting the fermentation ability. The thiobarbituric acid value reduced by 65.59%, and the resistant staling value increased by 26.56%. Moreover, the anti-staling index of the beer fermented with mutant strain increased by 2.64-fold than that from wild-type strain respectively. China has the most production and consumption of beer around the world, so the quality of beer has a significant impact on Chinese beer industry. The result of this study could help with the improvement of the quality of beer in China as well as around the world.

EFFECT OF REPLACING CORN AND SOYBEAN MEAL WITH BREWERS RICE AND DRIED DISTILLERS BREWERS YEAST ON PERFORMANCE OF GROWING-FINISHING PIGS

The objective of this study was to determine the ef fect of replacing corn and Soybean Meal (SBM) with Brewers Rice (BR) and Dried Distillers Brewers Yeast (DDBY), respectively, on ADG, G:F, Apparent Total Tract Digestibility (ATTD), fecal DM output and fecal loss of N and P of growingfinishing pigs. Sixty four Yorkshire x Duroc x Hamp shire crosses (BW = 73±5.7 kg) were randomly assigned to corn/SBM (CSM), BR/SBM (RSM), corn/DDBY (CBY) or BR/DDBY (RBY) diets. Compared with pigs finished on corn based diets, pi gs fed BR based diets gained faster (0.868 vs. 0.730 kg.pig -1 ; p<0.01) and had better gain to feed ratio (0.30 v s. 0.25; p<0.01). Pigs finished on RBY diet had the least fecal DM output (0.245, 0.352, 0 .575, 0.639 kg.pig -1 ; p<0.001) and greatest ATTD (91.5, 87.8, 80.0, 77.9%; p<0.001) followed by RSM, CBY and CSM pigs, respectively. Pigs finished on RBY diet lost the least (p<0.001) amount of N (0 .010, 0.013, 0.019, 0.021 kg.pig -1 ) and P (0.010, 0.014, 0.016, 0.019 kg.pig -1 ) in the feces followed by pigs finished on RSM, CB Y and CSM, respectively. In conclusion, BR and DDBY can replace all corn and SBM in swine diets with no negative effects on performance of growing-finishin g pigs.

Domesticating brewing yeast for decreasing acetaldehyde production and improving beer flavor stability

High level of acetaldehyde produced by yeast in beer industry, especially in China, is still an important issue. To obtain a brewing strain with low acetaldehyde, a novel approach, based on domestication by disulfiram–ethanol plates, was developed. A mutant D-A-14 with lower acetaldehyde was obtained with UV mutagenesis. Through longtime domestication, the mutant D-A-14 produced 60.57 % less (2.20 mg/L) than the Wt strain MA12. Besides, the ratio of higher alcohols to esters in beer fermented by the mutant D-A-14 (3.7) was lower than that of MA12 (5.8), which exhibited harmonious flavor. For further study, DNA microarray technique was exploited to analyze the changes in genes involved in metabolism between the Wt and mutant. The data of DNA microarray were consistent with the decrease in acetaldehyde, organic acids, and the ratio of higher alcohols to esters of mutant D-A-14. Therefore, the newly screened strain has the potential to be applied in the brewing industry.

Amino Acid Profile in Juvenile Pikeperch (Sander Lucioperca (L.)) - Impact of Supplementing Feed With Yeast Extract

Abstract The European pikeperch, Sander lucioperca (L.) is a valuable species in aquaculture, and its nutritious meat is highly regarded by consumers. The contents of indispensable dietary amino acids (IDAA) in pikeperch fillets is higher than in other fish species and exceed the adult recommended daily allowance of them. Increasingly, the fish meal and soya protein components of fish feed are being replaced with protein from brewer's yeast, Saccharomyces cerevisiae. The aim of this study was to determine the fatty acid profiles of juvenile pikeperch fed feeds supplemented with yeast extract and to determine the IDAA requirements of this species using the ideal protein method. It was demonstrated that supplementing feed with yeast extract did not have a significant impact on nutrient accumulation in the fish. Pikeperch requirements for exogenous amino acids is similar to that of rainbow trout at 26.2 g 100 g-1protein. Commercial feeds used in pikeperch culture contain sufficient quantities of essential amino acids.

Monitoring of the production of flavour compounds by analysis of the gene transcription involved in higher alcohol and ester formation by the brewer's yeastSaccharomyces pastorianususing a multiplex RT-qPCR assay

Lager yeast produces a broad range of aroma-active substances during fermentation, of which higher alcohols and volatile esters are vital for the complex flavour of beer. Lager yeast contains several genes that encode the proteins responsible for flavour production. Investigation of gene expression in the hybrid Saccharomyces pastorianus is meaningful as it combines genes from both S. cerevisiae (Sc-type) and S. bayanus (Sb-type). In this study, we developed a GeXP analyser-based multiplex polymerase chain reaction assay to simultaneously assess the transcription of BAP2, BAT1, BAT2, ATF1, ATF2, EEB1, EHT1 and IAH1, involved in higher alcohol and volatile ester biosynthesis, within the S. pastorianus genome from both sub-genomes. GeXP proved to be an effective method of performing a gene expression study by providing a continuous profile of the expression of multiplex genes. This offers the possibility of using this type of data to monitor and control fermentations. Profiles of higher alcohol and volatile ester formation, and the transcription of specific genes, indicated that the synthesis of flavour compounds appears to correlate, at least in part, to the transcription of certain genes. As well as the differential expression of various genes, the differential expression of orthologous genes was also observed during fermentation, suggesting that the Sc-type and Sb-type genes may have different functions. Our results will further the understanding and manipulation of the phenotype of commercially important lager yeasts. Copyright © 2014 The Institute of Brewing & Distilling

Yeast: the soul of beer’s aroma—a review of flavour-active esters and higher alcohols produced by the brewing yeast

Among the most important factors influencing beer quality is the presence of well-adjusted amounts of higher alcohols and esters. Thus, a heavy body of literature focuses on these substances and on the parameters influencing their production by the brewing yeast. Additionally, the complex metabolic pathways involved in their synthesis require special attention. More than a century of data, mainly in genetic and proteomic fields, has built up enough information to describe in detail each step in the pathway for the synthesis of higher alcohols and their esters, but there is still place for more. Higher alcohols are formed either by anabolism or catabolism (Ehrlich pathway) of amino acids. Esters are formed by enzymatic condensation of organic acids and alcohols. The current paper reviews the up-to-date knowledge in the pathways involving the synthesis of higher alcohols and esters by brewing yeasts. Fermentation parameters affecting yeast response during biosynthesis of these aromatic substances are also fully reviewed.

Antipyretic effect of ethanolic extract of Moringa oleifera leaves on albino rats

Objective The aim of the study was to evaluate the antipyretic activity of ethanolic leaf extract of Moringa oleifera using Brewer's yeast-induced pyrexia model. Materials and methods It was a randomized controlled experimental study. A total of 60 rats were taken, dividing them in six groups, each containing 10 rats. Ethanolic extract of M. oleifera (EMO) was administered at 50, 100, 200, and 400 mg/kg doses orally to the respective four groups. The control group was fed with normal saline at 2 ml/kg. A 20% suspension of Brewer's yeast in normal saline was injected subcutaneously at a dose of 10 ml/kg body weight below the nape of neck of rats in all groups. Pyrexia developed after 10 h of Brewer's yeast injection and the temperature was recorded. Animals which showed a rise in body temperature to at least 39°C were included in the study, allowing a minimal of six rats in each group, total of 36 rats. Drugs were given after development of pyrexia and temperatures were recorded. Paracetamol at 100 ml/kg orally was taken as the standard drug. Results The ethanolic leaf extract of M. oleifera showed significant (P Conclusion The ethanolic leaf extract of M. oleifera exhibited significant (P < 0.05) antipyretic activity at 100, 200, and 400 mg/kg.

Sensitization rates of causative allergens for dogs with atopic dermatitis: detection of canine allergen-specific IgE.

Allergen-specific IgE serology tests became commercially available in the 1980s. Since then these tests have been widely used to diagnose and treat allergic skin diseases. However, the relationship between a positive reaction and disease occurrence has been controversial. The purpose of this study was to evaluate allergens using a serologic allergy test in dogs with atopic dermatitis (AD). Dogs clinically diagnosed with AD (n=101) were tested using an allergen-specific IgE immunoassay. Among the total 92 environmental and food allergens, house dust and house dust mites were the most common. Several allergens including airborne pollens and molds produced positive reactions, and which was considered increasing allergens relating to the climate changes. The presence of antibodies against staphylococci and Malassezia in cases of canine AD was warranted in this study. Additionally, strong (chicken, turkey, brown rice, brewer's yeast, and soybean) and weakly (rabbit, vension, duck, and tuna) positive reactions to food allergens could be used for avoidance and limited-allergen trials.

Study on antipyretic activity of Rumex vesicarius leaves extract in albino rabbits

Aim: The present study was planned to investigate the possible antipyretic activity of methanolic leaves extract of Rumex vesicarius against various protocols of experimentally induced pyrexia in rabbits. Materials and Methods: Ninety healthy adult albino rabbits were divided into three groups (A, B, C), 30 rabbits in each group. Pyrexia was induced by three different protocols, i.e. boiled milk (0.5 ml/kg body weight, intra-peritonealy), Brewer's yeast (10 ml/kg, subcutenously) and D-amphetamine (5 mg/kg, i.p.), to the groups A, B and C respectively. Each group was further subdivided into five sub groups (1, 2, 3, 4 and 5) each having 6 animals. Sub group-1 served as positive control group; sub group-2 was treated with aspirin (10 mg/kg, orally) standard antipyretic agent; sub group-3, 4 and 5 were treated orally with methanolic leaves extract of Rumex vesicarius at dose rate of 80, 120 and 160 mg/kg body weight respectively. The hypothermic effect was observed at different time intervals in each protocol. Results: Rumex vesicarius L. significantly (p<0.05) lowered the elevated temperature in all scenarios. Maximum antipyretic effect was observed at 3h of post induction pyrexia in group A and at 4h after pyrexia in the groups B and C. Moreover, the antipyretic effect was concentration dependent and comparable to the standard aspirin at higher doses. Conclusion: The leaves of Rumex vesicarius have the antipyretic action in dose dependent manner, based upon this scientific validation, the claims of the local communities are true. The exact mode of action of this plant is still not clear, however, a single or a number of bioactive compounds of the plant may be responsible for its antipyretic activity.

Comparison of DNA Extraction Methods in Terms of Yield, Purity, Long-Term Storage, and Downstream Manipulation with Brewer's Yeast Chromosomal DNA

Five methods of DNA isolation (a “classical” phenol/chloroform extraction and four commercially available kits) were compared in terms of the yield, purity, integrity, and stability of extracted DNA from both laboratory and industrial yeast strains. DNA isolation with commercial kits employing silica-based adsorption columns mostly gave lower yields of DNA. The integrity of DNA soon declines and after 6 months of storage under the manufacturer's instructions, it was almost fully degraded. Isolation of DNA using bead breaking of cells resulted in very low yield and also low purity of the DNA. The use of a commercial kit without silica columns and phenol/chloroform treatment as well as the traditional phenol/chloroform extraction were certainly more time consuming, but the extracted DNA was of high purity and concentration, with minimal damage, stable over months, and usable for subsequent molecular analyses (cloning, PCR, RFLP, DNA sequencing). Only one kit based on lyticase treatment, salting out without phenol/chloroform treatment, and “classical” phenol/chloroform extraction method allowed us to isolate a high yield of DNA with sufficient purity and stability in comparison with the use of commercial kits based on silica columns.

Test-based exclusion diets in gastro-esophageal reflux disease patients: a randomized controlled pilot trial.

To investigate the clinical response of gastro-esophageal reflux disease (GERD) symptoms to exclusion diets based on food intolerance tests. A double blind, randomized, controlled pilot trial was performed in 38 GERD patients partially or completely non-responders to proton pump inhibitors (PPI) treatment. Fasting blood samples from each patients were obtained; leukocytotoxic test was performed by incubating the blood with a panel of 60 food items to be tested. The reaction of leukocytes (rounding, vacuolization, lack of movement, flattening, fragmentation or disintegration of cell wall) was then evaluated by optical microscopy and rated as follows: level 0 = negative, level 1 = slightly positive, level 2 = moderately positive, and level 3 = highly positive. A "true" diet excluding food items inducing moderate-severe reactions, and a "control" diet including them was developed for each patient. Then, twenty patients received the "true" diet and 18 the "control" diet; after one month (T1) symptoms severity was scored by the GERD impact scale (GIS). Hence, patients in the "control" group were switched to the "true" diet, and symptom severity was re-assessed after three months (T2). At baseline (T0) the mean GIS global score was 6.68 (range: 5-12) with no difference between "true" and control group (6.6 ± 1.19 vs 6.7 ± 1.7). All patients reacted moderately/severely to at least 1 food (range: 5-19), with a significantly greater number of food substances inducing reaction in controls compared with the "true" diet group (11.6 vs 7.0, P < 0.001). Food items more frequently involved were milk, lettuce, brewer's yeast, pork, coffee, rice, sole asparagus, and tuna, followed by eggs, tomato, grain, shrimps, and chemical yeast. At T1 both groups displayed a reduction of GIS score ("true" group 3.3 ± 1.7, -50%, P = 0.001; control group 4.9 ± 2.8, -26.9%, P = 0.02), although the GIS score was significantly lower in "true" vs "control" group (P = 0.04). At T2, after the diet switch, the "control" group showed a further reduction in GIS score (2.7 ± 1.9, -44.9%, P = 0.01), while the "true" group did not (2.6 ± 1.8, -21.3%, P = 0.19), so that the GIS scores didn't differ between the two groups. Our results suggest that food intolerance may play a role in GERD symptoms development, and leucocytotoxic test-based exclusion diets may be a possible therapeutic approach when PPI are not effective or indicated.

Followed extraction of β-glucan and mannoprotein from spent brewer's yeast (Saccharomyces uvarum) and application of the obtained mannoprotein as a stabilizer in mayonnaise

Abstract The aim of this study was to evaluate the viability of a novel method to extract both β-glucan and mannoprotein (MP) from the cell wall of spent brewer's yeast (Saccharomyces uvarum), particularly with the obtainment of MP by an additional step in a non-degrading procedure to extract β-glucan. The structure and composition of both obtained polymers were characterized, and the potential application of the MP as an emulsifier and stabilizing agent to replace xanthan gum (XG) in mayonnaise formulations was assessed. The yield obtained for β-glucan and MP was 10% and 4%, respectively. Infrared and nuclear magnetic resonance spectroscopy of β-glucan indicated a typical pattern of a glucose polymer with β-linkages. Analyses of the carbohydrate portion of MP revealed a retention factor of only 0.45, which indicates the presence of mannose; analyses of the protein portion of MP revealed 58-kDa and 64-kDa proteins that are largely composed (mg/g) of the amino acids valine (8.9%), aspartic acid (8.2%) and leucine (6.9%). The pH of the mayonnaise formulations containing different concentrations of MP (MP1: 0.6 g of MP/100 g; MP2: 0.8 g of MP/100 g; MP3: 1.0 g of MP/100 g) did not change (P ≥ 0.05) during 28 days of refrigerated storage. The stability of the MP1, MP2 and MP3 formulations increased during the assessed time (P ≤ 0.05) and after 28 days showed values higher than the formulation prepared with XG. All mayonnaise formulations prepared with MP exhibited high lightness (L* value) and a tendency toward decreased yellow color (b* value) during storage. Moreover, the formulations prepared with MP received similarly high scores (P > 0.05) for aroma, color, flavor and the overall evaluation without differences from that prepared with XG. Regarding the intent to purchase, the tasters generally reported the desire to purchase all of the tested mayonnaise formulations. The results presented herein demonstrated the feasibility of the proposed procedure to obtain both β-glucan and MP from spent brewer's yeast with a high yield and satisfactory purity. The obtained MP demonstrated good emulsifying and stabilizing properties, and its application to replace XG in the formulation of mayonnaise presented no negative effect on the sensory attributes of the product during refrigerated storage. Industrial relevance S. uvarum has been an interesting biotechnological tool for the production of beer using low fermentation, resulting in production of high amounts of brewer's yeast, which is commonly discarded. β-Glucan and mannoprotein (MP) obtained from spent brewer's yeasts have presented interesting biological properties, which could be applied for food production and conservation. Present study provides novel and valuable information concerning the viability of a followed method to extract β-glucan and MP from the cell wall of spent brewer's yeast (S. uvarum) discarded after fermentation processes, chiefly about the specific isolation of MP using an additional step in a non-degrading procedure that included sonication and proteolysis to extract β-glucan. The obtained MP revealed interesting emulsifying and stabilizing properties, and its use for the formulation of mayonnaise had no negative effect on the sensory properties of the product during refrigerated storage.

Oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) of β-glucans from different sources with various molecular weight

Abstract β -Glucans are major cell wall components in some cereal grains and fungi (yeast and mushrooms). The heterogeneity of β -glucans activity makes a distinction between the different sources. This study assessed oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) of oat β -glucans with different molecular weight (MW). ORAC and FRAP of β -glucans from different sources (oat, yeast, and fungi Schizophyllum commune ) were also evaluated. ORAC and FRAP values of β -glucans were significantly different not only among different MW but also among samples from different sources. β -Glucan from brewer's yeast extract with 0.2 kDa MW had the highest value of ORAC. Carboxymethyl yeast β -glucan C90 with 404 kDa MW exhibited the strongest FRAP values. As for β -glucans with different MW, 1800 kDa β -glucan possessed the highest ORAC value, and 1040 kDa β -glucan possessed the highest FRAP value. Tested 500 kDa oat β -glucan presented ORAC in a dose-dependent manner. These results indicate that molecular weight and source are the crucial factor for the antioxidant activity of β -glucan. A number of dietary β -glucan may serve as natural antioxidants to exert health promotion effects in neutraceuticals and cosmetics.

Brewer's yeast and sugarcane yeast as protein sources for dogs

Brewer's yeast (BY), autolysed sugarcane yeast (ASCY) and integral sugar cane yeast (ISCY) were studied in two experiments as ingredients for dog diets. In the first experiment, 28 dogs were randomly assigned to four diets; one reference diet and three test diets containing 15% of BY, ASCY or ISCY and 85% of the reference diet (as-fed basis). The digestibilities of the yeasts were calculated by the substitution method. In the second experiment, 35 dogs were randomized to five diets with similar chemical composition but different levels of sugarcane yeast inclusion (0%, 7.5% ASCY, 15% ASCY, 7.5% ISCY and 15% ISCY). In both experiments, the coefficient of total tract apparent digestibility (CTTAD) of nutrients was determined through total collection of faeces. During experiment, two additional analyses of food palatability, nitrogen balance and urea postprandial responses were performed. The data were submitted to analysis of variance, and the means were compared by orthogonal or polynomial contrasts or Tukey's test (p<0.05). In experiment 1, CTTAD of protein was lower for both sugarcane yeasts than for BY (p=0.012), as was metabolizable energy content (p=0.025). In experiment 2, a linear reduction in energy digestibility with ASCY inclusion (p=0.05) was verified. Furthermore, faecal score and DM content were reduced with ISCY inclusion (p<0.003). No effect of yeast inclusion on nitrogen balance or postprandial urea response was found. Also, the inclusion of 7.5% of ASCY or ISCY increased diet palatability (p<0.01). Yeasts present adequate digestibility by dogs, but its effect on faecal formation needs to be considered. No clear advantage for the use of ASCY over ISCY was found. In conclusion, we find that sugarcane yeast is suitable for inclusion in dog food and can enhance the overall palatability of the diet.

(نشطات نمو للنباتات(صديقة للبيئة

Been working in this research on the use of natural materials and plant extracts, namely, (brewer's yeast) and (extract licorice) where these materials used are environmentally friendly without any damage caused to humans or the environment, these natural materials are applied on different plants such as tomatoes and wheat and cowpea and ornamental plants such as plant Gazania SPLENDENS and some oil crops such as sunflower. The results show the process as the percentage increase in length for tomato plant which was about (107) cm and weight of the crop was about (1.165) kg of tomato treatment textured spray. Compared with tomato untreated textured spray with an increase in length (82) cm and crop yield (273) g. And plant wheat the increase in length (79) cm compared with the wheat untreated material reaching (60) cm and weight of the crop of wheat treatment textured spray was (45) g and untreated material about (31) g, and plant cowpea The increase in length of about (29) cm to lobby treatment textured spray compared with cowpea untreated material was increase in length (10) cm and weight of the crop of peas treatment was (3.57) g and untreated was (zero). The increase in length of the plant Gazania SPLENDENS treatment textured spray around (23) cm and Gazania SPLENDENS untreated material (18) cm, either sunflower treatment textured spray amounted increase in length (154) cm compared with sunflower untreated material about (75) cm and this shows that the materials used were doping substances of various plants has brought efficiency in the early vegetative growth and the speed growth, and also increase the quantity of production.

Improved sake metabolic profile during fermentation due to increased mitochondrial pyruvate dissimilation

Although the decrease in pyruvate secretion by brewer's yeasts during fermentation has long been desired in the alcohol beverage industry, rather little is known about the regulation of pyruvate accumulation. In former studies, we developed a pyruvate under-secreting sake yeast by isolating a strain (TCR7) tolerant to ethyl α-transcyanocinnamate, an inhibitor of pyruvate transport into mitochondria. To obtain insights into pyruvate metabolism, in this study, we investigated the mitochondrial activity of TCR7 by oxigraphy and (13) C-metabolic flux analysis during aerobic growth. While mitochondrial pyruvate oxidation was higher, glycerol production was decreased in TCR7 compared with the reference. These results indicate that mitochondrial activity is elevated in the TCR7 strain with the consequence of decreased pyruvate accumulation. Surprisingly, mitochondrial activity is much higher in the sake yeast compared with CEN.PK 113-7D, the reference strain in metabolic engineering. When shifted from aerobic to anaerobic conditions, sake yeast retains a branched mitochondrial structure for a longer time than laboratory strains. The regulation of mitochondrial activity can become a completely novel approach to manipulate the metabolic profile during fermentation of brewer's yeasts.

Ethanol fermentation of very high gravity (VHG) maize mashes by Saccharomyces cerevisiae with spent brewer's yeast supplementation

The subject of this research project was ethanol productivity from very high gravity maize mashes supplemented with spent brewer's yeast as a nutrient source. Batch fermentation of maize mashes (360 g of maize per kilogram of mash) supplemented with 30 g of spent brewer's yeast's wet biomass, dried spent brewer's yeast and yeast extract per kilogram of mash was conducted for 96 h at 30 °C. In all supplemented mashes higher ethanol production rate was observed in comparison to the control sample, especially in the initial stages of fermentation. After 96 h fermentation the ethanol concentration ranged from 120.95 to 142.34 g dm−3 in supplemented mashes (120.74 g dm−3 in the control sample) which corresponded with practical ethanol yields of 78.05–91.85% (77.91% in the control sample). It was also important that maximum ethanol yield in supplemented mashes was achieved after ca. 48 h and 72 h of fermentation while in the control sample ethanol production continued until the end of the process.

125thAnniversary Review: Developments in brewing and distilling yeast strains

Progress during the past 25 years regarding our knowledge of brewer's yeast strains is considered. This is not a comprehensive review but rather focuses on some specific areas. These areas include a brief description of genomics, proteomics and metabolomics as applied to brewer's yeast strains. This review subsequently considers differences between ale and lager yeast strains, the uptake and metabolism of wort sugars and amino acids, yeast flocculation, yeast management between fermentations and yeast strain genetic stability. The question of process intensification, with particular attention to high-gravity brewing, is also addressed. Fermentation systems and processes are considered with an emphasis on novel procedures for stirred fermentations. Copyright © 2013 The Institute of Brewing & Distilling