Active Dried Yeast Research Articles

The Impact of Lactic and Acetic Acid on Primary Beer Fermentation Performance and Secondary Re-Fermentation during Bottle-Conditioning with Active Dry Yeast

The presence of high concentrations of organic acids is known to adversely affect the efficiency and quality of ethanol fermentation. The growing popularity of sour beers warranted the exploration of strain-specific performance under optimal and suboptimal conditions similar to those found in sour beer production. The focus of this study was on the performance of select active dried yeast strains under artificially acidified conditions. Nine common brewing strains of active dried yeast were assessed based upon overall fermentation performance and their ability to metabolize maltotriose and maltose between 0.0% w/w − 1.0% w/w lactic acid and 0.0% w/w − 0.5% w/w acetic acid. A single strain of active dried yeast specifically selected and bred for bottle conditioning environments was assessed based upon its ability to metabolize glucose, and carbonate artificially acidified finished beer between 0.0%−1.6% w/w lactic acid and 0.0%−1.0% w/w acetic acid. This study confirmed the suitability of active dry brewing yeast for sour beer fermentations that meet or exceed the typical organic acid concentrations encountered in sour wort. The majority of the selected strains performed well in sour wort containing < 0.4% w/w lactic acid or < 0.1% w/w acetic acid. The importance of strain selection became apparent at concentrations exceeding these reported values, with two strains displaying almost no change in fermentation capabilities across the range of organic acid concentrations. Bottle conditioning remained unhindered by lactic acid up to 1.6% w/w, while acetic acid concentrations at and above 0.4% w/w significantly hindered bottle conditioning.

Effect of non-encapsulated and encapsulated active dried yeast on blood cell count, blood metabolites, and immune response of finishing beef heifers

A study was conducted to evaluate whether encapsulated active dried yeast (EDY), compared with non-protected active dried yeast (ADY) or antibiotics (ANT), improved immune response and blood metabolites of finishing beef heifers. Blood urea nitrogen was lower (P &lt; 0.05) with supplemented ADY and mixture of ADY and EDY (MDY) compared with control. Supplementation of MDY also resulted in lower (P &lt; 0.05) red blood cell distribution width than control. Lipopolysaccharide-binding protein was less (P &lt; 0.05) for EDY than control, ANT, and ADY as well as cytokine concentration of interleukin-6 was less (P &lt; 0.05) for MDY versus control.

PSXII-7 Supplementing beef cattle finishing diets with ruminal protected live yeast affected fatty acid profiles in meat

Abstract Fatty acid (FA) composition in beef is related to beef quality and human health. It was recently reported that feeding active dried yeast (ADY) in finishing bull altered some FA of longissimus muscle. The objective was to evaluate the effects of adding ruminally protected versus non-protected ADY on FA profiles of the pars costalis diaphragmatis (PCD) muscle of beef cattle. Seventy-five Angus steers (initial BW 448 kg) were assigned to a randomized complete block design with five treatments: control (no additives), antibiotics (ANT, 330 mg monensin + 110 mg tylosin/d), ADY (1.5 g/d), encapsulated ADY (EDY, 3 g/d) and combination of ADY and EDY (MDY). The encapsulated ADY consisted of 1.5 g ADY and 2 g capsule. Antibiotics, ADY and EDY were top-dressed to a diet containing 10% barley silage and 90% barley concentrate (DM basis). The PCD samples were collected from cattle at slaughter. Intakes (g/d) of total FA (144), saturated FA (SFA; 41), monounsaturated FA (MUFA, 16) and polyunsaturated FA (PUFA, 87) were not different among treatments. Proportion of SFA (49.0%) and MUFA (48.2%) in PCD did not differ among treatments, whereas the proportion of PUFA was greater (P &amp;lt; 0.05) with EDY (3.0%) and MDY (3.0%) than control (2.4%). The proportion of n-3 FA also tended (P &amp;lt; 0.06) to be greater with EDY (0.49%) and MDY (0.50%) than control (0.41%) and ADY (0.41%). Steers fed EDY and MDY enhanced (P &amp;lt; 0.05) the proportion of linoleic acid (LA n-6) and decosapentaenoic acid (DPA n-3) compared with control. These results indicated that feeding EDY and MDY increased amounts of PUFA, FA n-3, LA n-6 and DPA n-3. Inclusion of encapsulated yeasts to diet might increase the amount of bioactive yeasts reached intestines and result in better utilization of PUFA from the digesta and increase the accumulation in the intramuscular fat.

Fecal bacterial community of finishing beef steers fed ruminally protected and non-protected active dried yeast.

Our previous study suggested that supplementation of high-grain diets with ruminally protected and non-protected active dried yeast (ADY) may potentially reduce manure pathogen excretion by feedlot cattle. We hypothesized that feeding ruminally protected ADY might change the fecal bacterial community of finishing cattle. The objective of this study was to investigate the effects of feeding ruminally protected and non-protected ADY to finishing beef steers on their fecal bacterial community. Fresh fecal samples were collected on day 56 from 50 steers fed one of five treatments: 1) control (no monensin, tylosin, or ADY), 2) antibiotics (ANT, 330 mg monensin + 110 mg tylosin·steer-1d-1), 3) ADY (1.5 g·steer-1d-1), 4) encapsulated ADY (EDY; 3 g·steer-1d-1), and 5) a mixture of ADY and EDY (MDY; 1.5 g ADY + 3 g EDY·steer-1d-1). Bacterial DNA was extracted from fecal samples and sequenced using a MiSeq high-throughput sequencing platform. A total number of 2,128,772 high-quality V4 16S rRNA sequences from 50 fecal samples were analyzed, and 1,424 operational taxonomic units (OTU) were detected based on 97% nucleotide sequence identity among reads, with 769 OTU shared across the five treatments. Alpha diversity indices, including species observed, Chao estimate, abundance-based coverage estimator, Shannon, Simpson, and coverage, did not differ among treatments, and principal coordinate analysis revealed a high similarity among treatments without independent distribution. Bacteroidetes and Firmicutes were dominant phyla in the fecal bacterial community for all treatments, with a tendency (P < 0.10) for greater relative abundance of Bacteroidetes but lesser Firmicutes with ANT, EDY, and MDY compared with control steers. Prevotella was the dominant genus in all treatments and steers supplemented with ANT, EDY, and MDY had greater (P < 0.05) relative abundance of Prevotella than control steers, but lesser (P < 0.03) relative abundance of Oscillospira. No differences between ADY and control were observed for the aforementioned variables. Fecal starch contents were not different among treatments, but the relative abundance of Bacteroidetes, as well as Prevotella at genera level, tended (P < 0.06) to be positively correlated to fecal starch content. We conclude that supplementing ruminally protected or non-protected ADY or ANT had no effect on diversity and richness of fecal bacteria of finishing beef cattle, whereas feeding protected ADY or ANT to finishing beef steers altered the dominant fecal bacteria at phylum and genus levels. Therefore, supplementation of ruminally protected ADY may potentially improve intestinal health by stimulating the relative abundance of Prevotella.

Evaluation of active dried yeast in the diets of feedlot steers-I: Effects on feeding performance traits, the composition of growth, and carcass characteristics1.

The use of active dried yeast (ADY) in the diets of feedlot steers may improve feed efficiency, growth performance, and reduce days on feed. Strategic timing of ADY inclusion in the diet may increase feed conversion or aid in the dietary transition from growing to finishing diets. One hundred twenty steers, blocked by weight, were fed four diets for 164 d: grower (70 d), first transition diet (7 d), second transition diet for (7 d), and finisher (80 d) in a GrowSafe System. Four treatment sequences of ADY inclusion were evaluated in a Balaam's design where steers were fed a control diet before and after the grower phase (CC), control before and ADY after the grower phase (CY), ADY before and control after the grower phase (YC), and ADY before and after the grower phase (YY). A random coefficients model was used to evaluate the following variables of interest: feeding performance and growth traits, including biometric measurements and carcass ultrasound measurements, and carcass characteristics. Treatment was a fixed effect and block was a random effect. Treatment did not affect feeding performance or behavior (P ≥ 0.14). The rate of change of biometric measurements were not different (P ≥ 0.16) across treatment groups except for rib girth circumference, which was greater for the YY and CY groups intermediate for the CC group and least for the YC group (0.828 and 0.809 vs. 0.751 vs. 0.666 cm/d, respectively; P < 0.01). Faster growth rates of rib girth circumference resulted in larger final measurements for steers that were finished on ADY (P < 0.01). Ultrasound measurements (backfat, LM area, intra-muscular fat, and rump fat) were not different across treatments (P ≥ 0.15). However, there was a tendency for the YC group to have a slower rate of back fat deposition than other treatment groups (P = 0.09). Steers' final shrunk BWs did not differ (P = 0.61), but shrink percentage was greater for CC than for YY groups (3.7% vs. 2.7%, respectively; P = 0.05). Carcass characteristics were not different across treatments (P ≥ 0.20). Crude fat, CP, ash and moisture analyses of the 9th to 11th rib section were not different across treatments, and there was no difference in adjusted final shrunk BW (P ≥ 0.45). Feeding the ADY strain used in this study to growing and finishing feedlot steers increased rib girth circumference development rate and reduced shrink loss without affecting feeding behavior, feeding performance, or carcass characteristics.

Using ruminally protected and nonprotected active dried yeast as alternatives to antibiotics in finishing beef steers: growth performance, carcass traits, blood metabolites, and fecal Escherichia coli.

The objective of this study was to evaluate the effects of supplementing the diet of finishing beef steers with active dried yeast (ADY) in ruminally protected and nonprotected forms on growth performance, carcass traits, and immune response. Seventy-five individually-fed Angus steers (initial body weight (BW) ± SD, 448 ± 8.4 kg) were assigned to a randomized complete design with 5 treatments: 1) control (no monensin, tylosin, or ADY), 2) antibiotics (ANT, 330 mg monensin + 110 mg tylosin·steer-1d-1), 3) ADY (1.5 g·steer-1d-1), 4) encapsulated ADY (EDY; 3 g·steer-1d-1), and 5) a mixture of ADY and EDY (MDY; 1.5 g ADY + 3 g EDY·steer-1d-1). Active dried yeast with 1.7 × 1010 cfu/g was encapsulated in equal amounts of ADY and capsule materials (stearic acid and palm oil). Steers were fed a total mixed ration containing 10% barley silage and 90% barley-based concentrate mix (dry matter [DM] basis). The ANT, ADY, and EDY were top-dressed daily to the diet at feeding. Intake of DM, final BW, averaged daily gain (ADG), and gain-to-feed ratio (G:F) were unaffected by ADY or EDY. Carcass traits including hot carcass weight (HCW), dressing percentage, marbling score and quality grade did not differ among treatments, although fewer severely abscessed livers were observed (P < 0.05) with ADY and MDY compared with the other treatments. Plasma urea N tended (P < 0.10) to be greater in steers fed ANT, ADY, or EDY on day 56 and 112, while glucose remained stable in all treatments except greater (P < 0.02) plasma glucose occurred in steers fed MDY on day 112. Serum nonestrified fatty acid (NEFA) was unaffected by ADY or EDY, but it was greater (P < 0.03) in steers fed ANT compared with control. Plasma haptoglobin (Hp) and serum amyloid A (SAA) were affected by yeast supplementation on day 112, with greater (P < 0. 01) Hp in steers fed ADY, EDY, or MDY and lesser (P < 0.01) SAA in steers fed EDY and MDY than control. Lipopolysaccharide binding protein concentrations were greater (P < 0.01) in steers fed EDY and MDY on day 56. Supplementing with ADY (protected or nonprotected) or ANT had no effect on fecal IgA contents on day 56 and 112. Steers fed yeast (EDY or MDY) tended (P < 0.10) to have fewer fecal Escherichia coli counts than the control and ANT on day 56 and 112. These results indicate that feeding ADY to feedlot cattle may exhibit antipathogenic activity that conferred health and food safety beneficial effects including reduced liver abscess and potentially pathogen excretion, thus yeast may be an alternative to in-feed antibiotics in natural beef cattle production systems.

Effects of active dry yeast on ruminal pH characteristics and energy partitioning of finishing steers under thermoneutral or heat-stressed environment.

The objective of this trial was to determine the effects of supplementing active dried yeast (ADY) in the diets of finishing steers on energy and nitrogen metabolism and ruminal pH characteristics under thermoneutral (TN) or heat-stressed (HS) conditions. Eight British cross steers received 1 of 2 treatments (TRT) [either a control finishing diet (CON) or supplemented with 3 g/d of ADY] under 1 of 2 temperatures [TEMP: TN = 18 ± 0.55 °C and 20 ± 1.2% relative humidity (RH) or HS = 35 ± 0.55 °C and 42 ± 6.1% RH]. Steers were orally administered an indwelling rumen pH and temperature recording bolus. Data collection occurred for 48 consecutive hours inside 2 calorimetry chambers. Data were analyzed as a 4 × 8 Latin rectangle design with fixed effects of TRT and TEMP and random effects of steer and period. There were no TRT × TEMP interactions for metabolism or calorimetric measurements (P ≥ 0.1510). In vivo DM digestibility (DMD) was greater for ADY-fed steers than for CON-fed steers (77.1% vs. 75.3%, respectively; P = 0.0311). No TRT (P = 0.3032) or TEMP (P = 0.1833) effect was observed for nitrogen retention. Energy partitioning suggested DE and ME (Mcal/kg) were greater for ADY-fed steers than for CON-fed steers (P = 0.0097 and P = 0.0377, respectively). Steers under HS had reduced DMI but greater DMD than TN steers (77.1% vs. 75.3%, respectively; P = 0.0316) and greater CH4 per unit of DM (8.53 vs. 6.47 g/kg, respectively; P = 0.0145). Although DE was greater for HS than TN (3.16 vs. 3.06 Mcal/kg, respectively; P = 0.0123), heat production energy (HE) tended to be greater for HS than TN (18.1 vs. 17.0 Mcal/d, respectively; P = 0.0743), resulting in a less retained energy (0.412 vs. 0.100 Mcal/kg; P = 0.0147). There was a tendency for an interaction of mean ruminal pH (P = 0.1279) where pH of ADY-fed steers was greater than pH of CON-fed steers under TN conditions (5.81 vs. 5.57, respectively), but not under HS conditions (5.37 vs. 5.41, respectively). Duration (DUR) and area under the curve (AUC) for pH > 5.6 had similar tendencies; under TN conditions, the DUR and AUC for pH > 5.6 in ADY-fed steers were greater than in CON-fed steers (P = 0.0726 and P = 0.0954, respectively), but under HS conditions, there was no difference between ADY and CON. We conclude that supplementing ADY in the diets of finishing steers improved DMD, DE, ME, and mean ruminal pH under TN conditions, but not in extreme HS conditions likely due to reduced DMI and greater HE requirements.

Comparison of non-encapsulated and encapsulated active dried yeast on ruminal pH and fermentation, and site and extent of feed digestion in beef heifers fed high-grain diets

The objective of this study was to determine whether feeding ruminally protected active dried yeast (ADY) exhibits postruminal activity in comparison with feeding non-protected ADY assessed by measuring feed intake, ruminal pH and fermentation, and site and extent of feed digestion in finishing heifers. A combination antibiotic was used as a positive control. Five Angus beef heifers with ruminal cannulas (body weight of 650±48.8kg) were used in a 5×5 Latin square design with 21-d periods and 1 week of washout between each period. The five treatments were: 1) control (no ADY and no antibiotics), 2) antibiotics (ANT; 300mg monensin+110mg tylosin/d), 3) ADY (1.5g ADY/d), 4) encapsulated ADY (EDY; 3.5g/d containing 1.5g ADY and 2g capsule), and 5) mixture of ADY and EDY (MDY; 1.5g ADY+3.5g EDY/d). The ADY was encapsulated using barley hordein and glutelin extracted from barley grain. The stability of encapsulated yeast in the rumen and its release in the intestine were validated in vitro. Intake (kg/d) of dry matter (DM) was not affected by treatments. Ruminal pH, total volatile fatty acid (VFA) concentration, and NH3-N concentration did not differ among treatments, whereas molar proportion of acetate and ratio of acetate to propionate were greater with yeast addition than ANT. No treatment effects on flows of organic matter (OM) and starch to the omasum were observed, whereas flows of neutral detergent fibre (NDF) were greatest with ANT, lowest with EDY and intermediate with control, ADY and MDY (P<0.02). Digestibility of OM in the rumen tended (P<0.09) to be less with EDY or MDY than control or ANT, but no difference in ruminal digestibility of NDF and starch was observed among treatments. In contrast, greater postruminal digestibility of OM (P<0.01) and NDF (P<0.03) was observed with either EDY or MDY versus control and ANT. Digestibility of OM and NDF in the total digestive tract was also greater (P<0.01) with EDY or MDY than control. No treatment effect was observed on the flows of N to the omasum or microbial protein synthesis. Although digestibility of N in the rumen was not different, the digestibility of N in the total digestive tract was greater (P<0.02) with EDY or MDY than control or ANT. Supplementation of ADY or MDY tended (P<0.10) to have greater gene copy numbers of R. flavefaciens compared with ANT. Total protozoa counts were greater (P<0.01) in the rumen of heifers supplemented with ADY or MDY compared with control or ANT. These results demonstrate the postruminal activity of ADY and indicate the potential of feeding protected yeast to ruminants to increase intestinal digestibility of nutrients.

Effects of dietary supplementation of active dried yeast on fecal methanogenic archaea diversity in dairy cows

This study aimed to investigate the effects of dietary supplementation of different dosages of active dried yeast (ADY) on the fecal methanogenic archaea community of dairy cattle. Twelve multiparous, healthy, mid-lactating Holstein dairy cows (body weight: 584 ± 23.2 kg, milk produced: 26.3 ± 1.22 kg/d) were randomly assigned to one of three treatments (control, ADY2, and ADY4) according to body weight with four replicates per treatment. Cows in the control group were fed conventional rations without ADY supplementation, while cows in the ADY2 and ADY4 group were fed rations supplemented with ADY at 2 or 4 g/d/head. Real-time PCR analysis showed the populations of total methanogens in the feces were significantly decreased (P < 0.05) in the ADY4 group compared with control. High-throughput sequencing technology was applied to examine the differences in methanogenic archaea diversity in the feces of the three treatment groups. A total of 155,609 sequences were recovered (a mean of 12,967 sequences per sample) from the twelve fecal samples, which consisted of a number of operational taxonomic units (OTUs) ranging from 1451 to 1,733, were assigned to two phyla, four classes, five orders, five families and six genera. Bioinformatic analyses illustrated that the natural fecal archaeal community of the control group was predominated by Methanobrevibacter (86.9% of the total sequence reads) and Methanocorpusculum (10.4%), while the relative abundance of the remaining four genera were below 1% with Methanosphaera comprising 0.8%, Thermoplasma composing 0.4%, and the relative abundance of Candidatus Nitrososphaera and Halalkalicoccus being close to zero. At the genus level, the relative abundances of Methanocorpusculum and Thermoplasma were increased (P < 0.05) with increasing dosage of ADY. Conversely, the predominant methanogen genus Methanobrevibacter was decreased with ADY dosage (P < 0.05). Dietary supplementation of ADY had no significant effect (P > 0.05) on the abundances of genera unclassified, Candidatus Nitrososphaera, and Halalkalicoccus. In conclusion, supplementation of ADY to the rations of dairy cattle could alter the population sizes and composition of fecal methanogenic archaea in the feces of dairy cattle. The decrease in Methanobrevibacter happened with a commensurate increase in the genera Methanocorpusculum and Thermoplasma.

Effects of dietary active dried yeast (Saccharomyces cerevisiae) supply at two levels of concentrate on energy and nitrogen utilisation and methane emissions of lactating dairy cows

Twenty early lactation dairy cows were used to evaluate the effects of the dietary addition of an active dried yeast product at two levels of concentrate on productive performance, nutrient digestibility, methane (CH4) emissions and energy and nitrogen utilisation. This study was a replicated 4 × 4 Latin square design with a two (concentrate level) × two (yeast supplement) factorial treatment arrangement, with four periods (6 week/period) and a 3-week interval between each period. Cows were offered grass silage-based diets consisting of two levels of concentrate (300 and 600 g/kg), with or without supplement of 0.5 g/day of an active dry yeast (Saccharomyces cerevisiae strain) with a specification of 2 × 1010 cfu/g. Feed dry matter intake, milk yield, milk composition, bodyweight and body condition score were similar between yeast treatments at both concentrate levels. Nutrient digestibility was not affected by yeast supplementation. Energy intake and faecal, urinary, CH4 and milk energy outputs were also not affected by yeast supplementation. Yeast supplementation had no effects on energy partitioning but tended to increase heat production and decreased energy retention. Yeast supplementation at two levels of concentrate had no effect on total CH4 emissions, but tended to increase CH4 per unit of feed intake and CH4 energy output per unit of gross energy intake. There were no effects of yeast supplementation on CH4 per unit of milk yield. Yeast supplementation had no effect on any variable of nitrogen intake, output or utilisation. Overall, the dietary addition of an active dried yeast product at two concentrate feeding levels had no effects on feed intake, milk production, milk composition, nutrient digestibility, or nitrogen utilisation efficiency and only tended to increase heat production, CH4 per unit of feed intake and CH4 energy output per unit of gross energy intake in lactating dairy cows.

Effects of supplementation of active dried yeast and malate during sub-acute ruminal acidosis on rumen fermentation, microbial population, selected blood metabolites, and milk production in dairy cows

The objective of this study was to evaluate the effects of dietary supplementation of malate (MAL) and active dried yeast (ADY) on feed intake, rumen fermentation parameters, rumen microbial populations, selected blood metabolites, and milk production during a sub-acute ruminal acidosis (SARA) challenge in primiparous lactating dairy cows. Six rumen-fistulated Holstein dairy cows (body weight: 630±55kg, 110±25 days in milk, mean±SD) were assigned to the following treatments in a 3×3 Latin square design: (1) control TMR (CON); (2) a TMR supplemented with 80g of sodium–calcium malate/head per day (MAL); and (3) a TMR supplemented with 10g of active dried yeast providing 20×109 CFU of Saccharomyces cerevisiae/head per day (ADY). Each experimental period consisted of 14 days of adaptation to the experimental treatments, 4 days of SARA challenge, and 10 days of rest. Dry matter intake (18.4 vs. 19.8kg/day), and milk yield (29.3 vs. 30.4kg/day) were depressed during SARA compared with adaptation. Malate and ADY had no effect on DMI and milk yield during the adaptation and SARA phases. Malate and ADY had no effect on ruminal pH characteristics during adaptation. During SARA, maximum and mean ruminal pH was not affected by supplementation, but minimum ruminal pH tended to be higher for ADY compared to CON and MAL. Time spent with ruminal pH <5.6 and < 5.8 tended be lower for ADY compared to CON. During adaptation, ADY tended to decrease rumen NH3-N concentration compared to CON. Malate and ADY had no effect on selected blood metabolites, but glucose and insulin concentration increased during SARA compared to adaptation. The population of Fibrobacter succinogenes tended to increase with MAL and ADY during adaptation, but its population was decreased during SARA compare with adaptation. During SARA, the abundance of Megasphaera elsdenii tended to be higher for ADY than for MAL. The abundance of Streptococcus bovis increased during SARA, but was not affected by MAL or ADY supplementation. The relative abundances of protozoa in the rumen decreased during SARA. In conclusion, ADY supplementation to dairy cows with SARA can potentially improve rumen function, as indicated by a tendency for an improved ruminal pH and greater abundance of M. elsdenii within the rumen. However, supplementation of MAL provided no benefit to dairy cows under SARA condition, at least with the inclusion rates used in this study.

Production, reactivation and nutrient requirements of active dried yeast in winemaking: theory and practice

Wine yeast, from production to application, traverse an incredible range of environments. Central to their ability to not only survive but to thrive throughout this journey is their capacity to transform themselves in response to the varied conditions encountered. Wine yeast resilience alone, however, is insufficient. Producers and winemakers must be assiduous in their use of wine yeast with an understanding of yeast requirements throughout the process to achieve optimal results. Active dried yeast (ADY) starter cultures for initiating grape must fermentations are convenient, reliable and available for a wide range of strains suited to different wine types. These benefits cannot be fully realised without optimisation of: their production; reactivation of the dried product prior to inoculation; and appropriate nutrient management during fermentation. This review discusses current knowledge on production of Saccharomyces ADY for greatest biological stability and activity, and factors that affect their activity following rehydration and inoculation into grape must. The efficacy of various types of commercial additives used in reactivation of ADY and, winemaking interventions and nutrients that are used to optimise fermentation are also discussed.

Antioxidant defense parameters as predictive biomarkers for fermentative capacity of active dried wine yeast

The production of active dried yeast (ADY) is a common practice in industry for the maintenance of yeast starters and as a means of long term storage. The process, however, causes multiple cell injuries, with oxidative damage being one of the most important stresses. Consequentially, dehydration tolerance is a highly appreciated property in yeast for ADY production. In this study we analyzed the cellular redox environment in three Saccharomyces cerevisiae wine strains, which show markedly different fermentative capacities after dehydration. To measure/quantify the effect of dehydration on the S. cerevisiae strains, we used: (i) fluorescent probes; (ii) antioxidant enzyme activities; (ii) intracellular damage; (iii) antioxidant metabolites; and (iv) gene expression, to select a minimal set of biochemical parameters capable of predicting desiccation tolerance in wine yeasts. Our results show that naturally enhanced antioxidant defenses prevent oxidative damage after wine yeast biomass dehydration and improve fermentative capacity. Based on these results we chose four easily assayable parameters/biomarkers for the selection of industrial yeast strains of interest for ADY production: trehalose and glutathione levels, and glutathione reductase and catalase enzymatic activities. Yeast strains selected in accordance with this process display high levels of trehalose, low levels of oxidized glutathione, a high induction of glutathione reductase activity, as well as a high basal level and sufficient induction of catalase activity, which are properties inherent in superior ADY strains.

Impact of mixed S. cerevisiae strains on the production of volatiles and estimated sensory profiles of Chardonnay wines

The global wine industry is mostly reliant on the use of active dry yeasts to conduct wine fermentations. The use of single industrial yeasts, however, may result in the loss of complexity or uniqueness of the wine bouquet; the option of fermenting grape musts with multiple active dried yeast strains could enhance the complexity and quality of wines. Two novel Burgundian Saccharomyces cerevisiae strains (C2, C6) were compared with six industrial yeast strains for fermentation of Chardonnay must. The volatile compounds in the wines were identified and quantified using gas chromatography–mass spectrometry. The concentrations of 18 volatile compounds (higher alcohols, ethyl esters, acetate esters, acetaldehyde, acetic acid) were compared using analysis of variance and radar diagrams. The concentration of volatile compounds in wines produced by industrial and Burgundian strains differed significantly. Principal component analyses of the volatile compounds (higher alcohols, ethyl esters, acetate esters) in the wines revealed that fermentations with individual and mixed Burgundian strains were more similar to one another than wines fermented with industrial strains. Calculation of odor active values (OAVs) allowed estimation of the sensory impact of each volatile compound. Radar diagrams of the OAVs revealed the estimated sensory profiles of the wine produced by industrial and Burgundian (individual, mixed) strains. The most distinguishing trait of the mixed novel Burgundian yeast strains was that they produced intermediate concentrations of most volatile compounds and that production of fruity aromas such as sweet fruit, strawberry, green apple, pear and banana were above the sensory threshold, while the production of nail polish, waxy, balsamic and vinegar were below the human perception threshold. The mixed culture of Burgundian yeast strains produced wines that were unique and more complex than wines produced with single industrial yeast strains.

Saccharomyces cerevisiae Biodiversity During the Brewing Process of an Artisanal Beer: A Preliminary Study

J. Inst. Brew. 117(3), 352–358, 2011 In this study we investigated the biodiversity of Saccharomyces cerevisiae during the brewing of an artisanal beer, as well as during its storage in the bottle for 107 days at 20°C. After inoculation with an active dried yeast (ADY), the yeast counts were followed during fermentation and after bottling. Yeast loads remained stable at 10 6 –10 7 colony forming units (cfu)/mL, and only after day 21, were they were reduced to 10 4 cfu/mL. After three months in the bottle they spanned 10 2 –10 5 cfu/mL. Almost all isolated yeasts were identified as S. cerevisiae and after molecular characterization, unexpected results were obtained. The ADY did not take over the fermentation process and only after 21 days did isolates from the beer share similarities with the inoculated strain. During storage, a high diversity was found, underlining that each bottle developed its own micro-ecosystem. This study highlighted the necessity for better investigations of S. cerevisiae population dynamics during artisanal brewing. Even when the chemical parameters measured confirmed a correct fermentation process, the inoculated strain was not the main yeast involved in the fermentation and consequently, the final product may have different sensory characteristics from the ones expected by the producers.

Dried Yeast: Impact of Dehydration and Rehydration on Brewing Yeast DNA Integrity

As a consequence of fluidized bed drying, yeast cells may be exposed to a series of physiological stresses, of which the most evident is water loss. Desiccation can lead to cell wall crenellation, cytoplasmic crowding, loss of DNA supercoiling, membrane disruption, phase transitions, and ultimately cell death. Although the dehydrated phenotype has been well characterized, the sequence of events that causes damage to the cell has not been widely reported. Here we investigate the impact of dehydration and rehydration on the stability of the brewing yeast genome, including both the chromosomal and mitochondrial DNA (mtDNA). Analysis of rehydrated and control yeast populations for chromosome length polymorphisms (karyotyping), DNA sequence changes (PCR analysis of interdelta sequences), gross mitochondrial damage (presence of respiratory deficient mutants), and mitochondrial sequence changes (mtDNA RFLP [restriction fragment length polymorphisms]) indicated that the genetic constitution of dried yeast is not affected by the drying process. Active dried yeast (ADY) populations also demonstrated an enhanced tolerance to mutagen challenge (targeted at mtDNA), suggesting that the susceptibility of mtDNA to change is not associated with fluidized bed drying. These results demonstrate that the genetic stability of ADY is comparable to control populations.

Serial Repitching of Dried Lager Yeast

To demonstrate the suitability of active dried yeast (ADY) for serial repitching, dried and wet yeast slurries derived from the same strain were analyzed for five consecutive fermentations (G0–G4). In each instance, cell viability was determined prior to pitching, while yeast performance was assessed by analyzing fermentation profiles and the characteristics of the final products. In addition, beers produced using wet and dried G0 and G4 yeast were analyzed and compared for their concentrations of esters and higher alcohols. Yeast obtained at the end of each fermentation was screened for the presence of respiratory-deficient mutants and flocculent variants. Yeast slurries recovered from G4 beer were examined for genetic changes, as characterized by movement of Ty elements and chromosome length polymorphisms. This study shows that serially repitched wet and dried yeasts perform in a similar fashion and that repitched cultures exhibit more typical fermentation and flavor profiles than fresh slurries. In addition, the study demonstrates that the accumulation of genetic and phenotypic variants is not associated with serial repitching of dried yeast cultures. Consequently, it is proposed that ADY can be reused in a similar fashion to wet yeast without any adverse effects on fermentation performance, yeast quality, or flavor production.