Fermentation Traits Research Articles

Hybridization and adaptive evolution of diverse Saccharomyces species for cellulosic biofuel production

BackgroundLignocellulosic biomass is a common resource across the globe, and its fermentation offers a promising option for generating renewable liquid transportation fuels. The deconstruction of lignocellulosic biomass releases sugars that can be fermented by microbes, but these processes also produce fermentation inhibitors, such as aromatic acids and aldehydes. Several research projects have investigated lignocellulosic biomass fermentation by the baker’s yeast Saccharomyces cerevisiae. Most projects have taken synthetic biological approaches or have explored naturally occurring diversity in S. cerevisiae to enhance stress tolerance, xylose consumption, or ethanol production. Despite these efforts, improved strains with new properties are needed. In other industrial processes, such as wine and beer fermentation, interspecies hybrids have combined important traits from multiple species, suggesting that interspecies hybridization may also offer potential for biofuel research.ResultsTo investigate the efficacy of this approach for traits relevant to lignocellulosic biofuel production, we generated synthetic hybrids by crossing engineered xylose-fermenting strains of S. cerevisiae with wild strains from various Saccharomyces species. These interspecies hybrids retained important parental traits, such as xylose consumption and stress tolerance, while displaying intermediate kinetic parameters and, in some cases, heterosis (hybrid vigor). Next, we exposed them to adaptive evolution in ammonia fiber expansion-pretreated corn stover hydrolysate and recovered strains with improved fermentative traits. Genome sequencing showed that the genomes of these evolved synthetic hybrids underwent rearrangements, duplications, and deletions. To determine whether the genus Saccharomyces contains additional untapped potential, we screened a genetically diverse collection of more than 500 wild, non-engineered Saccharomyces isolates and uncovered a wide range of capabilities for traits relevant to cellulosic biofuel production. Notably, Saccharomyces mikatae strains have high innate tolerance to hydrolysate toxins, while some Saccharomyces species have a robust native capacity to consume xylose.ConclusionsThis research demonstrates that hybridization is a viable method to combine industrially relevant traits from diverse yeast species and that members of the genus Saccharomyces beyond S. cerevisiae may offer advantageous genes and traits of interest to the lignocellulosic biofuel industry.

Differences in the nutrient concentrations, in vitro methanogenic potential and other fermentative traits of tropical grasses and legumes for beef production systems in northern Australia.

In northern Australia, beef cattle grazed extensively on tropical rangelands are responsible for 5% of the nation's total greenhouse gas emissions. Methane (CH4 ) is a potent greenhouse gas and in grazing ruminants might be mitigated by selecting forages that, when consumed, produce less CH4 when fermented by rumen microbes. This study examined variability in the in vitro fermentation patterns, including CH4 production of selected tropical grasses and legumes, to identify candidates for CH4 mitigation in grazing livestock in northern Australia. Nutritive values and fermentation parameters varied between plant species and across seasons. Grasses with a relatively low methanogenic potential were Urochloa mosambicensis (wet summer), Bothriochloa decipiens (autumn), Sorghum plumosum (winter) and Andropogon gayanus (spring), while the legumes were Calliandra calothyrsus (wet summer and autumn), Stylosanthes scabra (winter) and Desmanthus leptophyllus (spring). There was some correlation between CH4 production and overall fermentation (volatile fatty acid concentrations) in grasses (R2 = 0.67), but not in legumes (R2 = 0.01) and there were multiple plants that had lower CH4 not associated with reduction in microbial activity. Differences in nutrient concentrations of tropical grasses and legumes may provide opportunities for productive grazing on these pastures, while offering some CH4 mitigation options in the context of northern Australian extensive beef farming systems. © 2017 Society of Chemical Industry.

Recent progress in the research about Propionibacterium acnes strain diversity and acne: pathogen or bystander?

Recent progress has steadily reported the existence of the diverse strains of Propionibacterium acnes, and these studies have contributed to the elucidation of their contradictory roles between normal commensals and pathogens. In this review, the authors aimed to provide an update on the recent understanding of research about P. acnes strain diversity and acne, analyzing the potential implications for clinical applications. Before the era of genomic research, P. acnes was known to be distinguished based on serological agglutination tests, cell wall sugar analysis, or fermentation traits. Since the complete genome sequence of P. acnes was first deciphered, genetic studies based on sequence data have expanded with the introduction of more refined and precise DNA-based typing methods, including multilocus sequence typing and metagenomics. These sophisticated techniques have revealed that P. acnes consists of phylogenetically distinct cluster groups with various pathogenic traits, including elicitation of inflammation, protein secretome profile, and unique distribution patterns in various skin loci. In following large-scale studies from patients' acne samples have revealed that specific sequence types are included within the phylogenetic divisions and further suggested that particular P. acnes strains play an etiologic role in acne while others are associated with health, providing a firm platform for evidential-based research into the exact role of this organism in acne. We strongly believe that future research would provide fruitful results in not only clarifying the apparent controversy with respect to roles of P. acnes but also developing therapeutic drugs by pinpointing specific targets of the pathogenic strain only.

Effect of diet supplementation with live yeast Saccharomyces cerevisiae on growth performance, caecal ecosystem and health of growing rabbits

<p>The aim of this study was to determine the effect of the live yeast Saccharomyces cerevisiae on the growth performance, caecal ecosystem and overall health of growing rabbits. A control diet was formulated (crude protein: 15.9%; neutral detergent fibre: 31.6%) and another diet obtained by supplementing the control diet with 1 g of Saccharomyces cerevisiae (6.5×109 colony-forming units) per kg of diet. Ninety 35-d old rabbits were allotted into 3 groups: TT (rabbits offered the supplemented diet from 17 d of age onwards), CT (rabbits offered supplemented diet from 35 d) and CC (rabbits fed non-supplemented diet). Body weight (BW) and feed intake were measured weekly and mortality was controlled daily. At 35, 42 and 77 d of age, 6 rabbits from each group were slaughtered and digestive physiological traits, serum clinical chemistry parameters, fermentation traits, and the composition of caecal microbiota examined. At 42 and 56 d of age, 10 rabbits from each group were injected intraperitoneally with 100 μg/animal of ovalbumin and blood samples were collected for examination of plasma immunological parameters. Throughout the experiment (5-11 wk), weight gain and feed intake (37.8 and 112.6 g/d, on av.) were not affected by yeast, except for weight gain in the first week after weaning, which was the highest in TT animals among the 3 groups (48.1 vs. 43.9 and 44.2 g/d for TT, CC and CT, respectively; P=0.012). This may be due to the increased trend in feed intake (P=0.072) in the TT group (96.4 g/d) compared to the others. Mortality (5/90) was low and did not differ among the 3 groups. Treatments had no effect on slaughter traits at the 3 sampling dates (35, 42 and 77 d). Only the weight of the empty caecum (% BW) was higher (P=0.02) in CC (2.2%) and CT (2.3%) than in TT group (1.8%) at 77 d of age. Treatments did not overtly affect the caecal microbiota, although the number of total anaerobic bacteria and Bacteroides were lower (108 and 107/g caecal digesta, respectively) in rabbits from CC group compared to those of CT and TT groups at 42 d of age (P=0.03). No difference between groups was observed for caecal short chain fatty acids profile, blood traits, or IgG and cytokine profile. In conclusion, supplementation of feed with yeast did not modify growth traits and resulted in only a temporary increase in weight gain and a slightly altered caecal microbiota after weaning.</p>

Quantitative proteomic analysis of the Saccharomyces cerevisiae industrial strains CAT-1 and PE-2

Brazilian ethanol fermentation process commonly uses baker's yeast as inoculum. In recent years, wild type yeast strains have been widely adopted. The two more successful examples are PE-2 and CAT-1, currently employed in Brazilian distilleries. In the present study, we analyzed how these strains compete for nutrients in the same environment and compared the potential characteristics which affect their performance by applying quantitative proteomics methods. Through the use of isobaric tagging, it was possible to compare protein abundances between both strains during the fermentation process. Our results revealed a better fermentation performance and robustness of CAT-1 strain. The proteomic results demonstrated many possible features that may be linked to the improved fermentation traits of the CAT-1. Proteins involved in response to oxidative stress (Sod1 and Trx1) and trehalose synthesis (Tps3) were more abundant in CAT-1 than in PE-2 after a fermentation batch. Tolerance to oxidative stress and trehalose accumulation were subsequently demonstrated to be enhanced for CAT-1, corroborating the comparative proteomic results. The importance of trehalose and the antioxidant system was confirmed by using mutant stains deleted in Sod1, Trx1 or Tps3. These deletions impaired fermentation performance, strengthening the idea that the abilities of accumulating high levels of trehalose and coping with oxidative stress are crucial for improving fermentation. SignificanceThe importance of the present works emerges from the necessity to better understand the peculiar biological features from two important bioethanol industrial strains of Saccharomyces cerevisiae during batch fermentation. We applied an iTRAQ-based quantitative proteomics analysis to compare these two important strains during batch fermentation and identified possible features involved in the fermentation performance. The results provided by this work will serve as an initial framework for future investigations on the biology of both strains.

Efecto del picado sobre las características nutricionales y fermentativas de ensilajes de pastos Kikuyo, Ryegrass perenne y Alpiste forrajero

Se evaluó el efecto del picado sobre las características nutricionales y fermentativas de ensilajes elaborados con 3 pastos (kikuyo, ryegrass perenne y alpiste forrajero). Se elaboraron 2 microsilos de cada pasto en bolsas de polietileno con capacidad para 1 kg, aplicando 2 tratamientos (picado y sin picar); se adicionó a cada microsilo 3% de melaza y 0,1% de un inóculo artesanal (hecho de leche agria, suero de queso y melaza). La especie de pasto tuvo el mayor impacto sobre las características nutricionales y fermentativas de los microsilos, mientras que el picado no mostró tendencia clara sobre los parámetros evaluados. El contenido de PC (14,40 a 19,35%), FDN (46,25 a 63,16%) y la DIVMS (46,15 a 65,55%) en los ensilados es indicador de su potencial para llenar gran parte de los requerimientos nutricionales del ganado lechero. El pasto ryegrass ensilado alcanzó los niveles de pH (4,41 a 4,83) menores y el pasto kikuyo los valores menores de capacidad amortiguadora (79,12 a 81,17 mEq NaOH 100 g-1 MS) y de nitrógeno amoniacal (1,03 a 1,33%). Los ensilajes elaborados con pastos pueden utilizarse como suplementos con valor nutricional superior a los henos utilizados en las raciones de ganado lechero en zonas altas.

Bacillus sp. strains to produce bio-hydrogen from the organic fraction of municipal solid waste

Bio-hydrogen, obtained by fermentation of organic residues, is considered a promising source of renewable energy. However, the industrial scale H2 production from organic waste is far to be realized as technical and economical limitations have still to be solved. Low H2 yields and lack of industrially robust microbes are the major limiting factors.To look for bacteria with both interesting hydrogen fermentative traits and proper robustness, granular sludge from a brewery full scale Upflow Anaerobic Sludge Blanket (UASB) digester was selected as trove of microbes processing complex substrates. One hundred and twenty bacterial strains, previously isolated from heat-treated granular sludge and genetically identified by 16S rDNA sequencing, were screened for extracellular hydrolytic enzymes on cellulose, hemicellulose, starch, pectin, lipids, protein. The most interesting hydrolytic strains were assessed for their H2 production from glucose and soluble starch. Two Bacillus sp. strains, namely F2.5 and F2.8, exhibited high H2 yields and were used as pure culture to convert Organic Fraction of Municipal Solid Waste (OFMSW) into hydrogen. The strains produced up to 61mL of H2 per grams of volatile solids and could be considered as good candidates towards the development of industrially relevant H2-producing inoculants. This is the first successful application of pure microbial cultures in bio-hydrogen production from OFMSW.

Non-conventional Yeast Species for Lowering Ethanol Content of Wines

Rising sugar content in grape must, and the concomitant increase in alcohol levels in wine, are some of the main challenges affecting the winemaking industry nowadays. Among the several alternative solutions currently under study, the use of non-conventional yeasts during fermentation holds good promise for contributing to relieve this problem. Non-Saccharomyces wine yeast species comprise a high number or species, so encompassing a wider physiological diversity than Saccharomyces cerevisiae. Indeed, the current oenological interest of these microorganisms was initially triggered by their potential positive contribution to the sensorial complexity of quality wines, through the production of aroma and other sensory-active compounds. This diversity also involves ethanol yield on sugar, one of the most invariant metabolic traits of S. cerevisiae. This review gathers recent research on non-Saccharomyces yeasts, aiming to produce wines with lower alcohol content than those from pure Saccharomyces starters. Critical aspects discussed include the selection of suitable yeast strains (considering there is a noticeable intra-species diversity for ethanol yield, as shown for other fermentation traits), identification of key environmental parameters influencing ethanol yields (including the use of controlled oxygenation conditions), and managing mixed fermentations, by either the sequential or simultaneous inoculation of S. cerevisiae and non-Saccharomyces starter cultures. The feasibility, at the industrial level, of using non-Saccharomyces yeasts for reducing alcohol levels in wine will require an improved understanding of the metabolism of these alternative yeast species, as well as of the interactions between different yeast starters during the fermentation of grape must.

Variability in microbial population and fermentation traits at various sites within the forestomach and along the digestive tract as assessed in goats fed either grass or browse

ABSTRACT In ruminants, feed is digested mainly in the reticulorumen but to some extent also in the hindgut, and the digestive processes are influenced by the diet. The aim of the study was to record changes in microbial population and fermentation along the digestive tract by considering defined rumen compartments, caecum and colon as assessed in goats fed two contrasting diets. Ten adult female Saanen goats were fed either on grass hay (‘grass’) or a 1:1:1 mixture of dried poplar, raspberry and chestnut leaves (‘browse’). After at least 20 days on feed and 12 h of fasting, the goats were euthanised and frozen in the natural resting position to allow sampling of contents from exactly defined gastrointestinal locations. Lyophilised rumen and hindgut contents were used for isolation of genomic DNA and microbial quantification via real-time PCR. In filtered rumen and hindgut fluid, pH and concentrations of ammonia and short-chain fatty acids (SCFA) were measured. The experiment demonstrated that, within the rumen, the dry matter content decreased from dorsal and central (132 g/kg) to the ventral compartment (62 g/kg) as expected. The abundances of total and fibrolytic bacteria, protozoa and methanogens as well as SCFA concentrations were similar in the cranial and caudal dorsal and central rumen, but were lower in the ventral rumen compartment. Additionally, SCFA concentration and pH close to the rumen wall in the central rumen compartment resembled those in the ventral rumen more closely than those in the other central rumen samples. The pH was lower in the dorsal and central (6.4) than in the ventral (7.5) rumen compartment. In the caecum and colon, respectively, the copy numbers of bacteria (3.8 and 6.2 × 10 10 /ml), protozoa (1.4 and 0.2 × 10 7 /ml) and methanogens (4.0 and 3.5 × 10 8 /ml) (means of all goats combined) were markedly lower than those found in the rumen even though SCFA concentrations were similar. For all variables measured, the differences within the rumen and along the digestive tract were more pronounced in the browse-fed compared to the grass-fed goats. Consistent with the higher nutritional quality of the browse, the concentration of fermentation end-products and nitrogen availability were higher in the rumen across all compartments in the browse-fed goats compared to the grass-fed goats (pH, 6.4 vs. 7.3; SCFA, 139 vs. 111 mmol/L; ammonia, 11.2 vs. 4.1 mmol/L; copy numbers of bacteria, 8.1 vs. 7.8 × 10 10 /ml; protozoa, 1.7 vs. 0.3 × 10 9 /ml; methanogens, 2.4 vs. 1.3 × 10 9 /ml). Different from that, the hindgut pH was higher and ammonia concentration was lower in browse-fed goats compared to grass-fed goats. The results demonstrated that, when collecting rumen digesta to study the microbial population and rumen fermentation, it is important to distinguish between dorsal/central and ventral rumen sampling points and to consider forage type and quality. However, it is not decisive to distinguish between caudal and cranial rumen regions, provided the sampling is not done in rumen wall proximity and not in close proximity to the oesophagus.

Effect of cereal processing (grinding to 3·5 mm or dry-rolling) in maize- or barley-based high-concentrate diets on rumen environment of beef cattle during the late fattening period

SUMMARYThe type and processing of cereals for beef cattle are key factors to maximize performance without increasing the risk of ruminal acidosis. The current work studied the effect of grinding (G) or dry-rolling (R) the cereals in a concentrate based on maize (M) or barley (B) on the rumen environment of eight 6-month-old Holstein calves, which received either M or B for 70 days, offered as G and R in two consecutive periods. Daily feed intake pattern, rumen fermentation traits, total rumen bacteria and relative proportions ofStreptococcus bovisandSelenomonas ruminantiumwere characterized twice in each period at 0, 4 and 8 h after feeding. Dry-rolling promoted a 0·25 reduction of concentrate intake during the first 4 h after feeding. Neither cereal type nor its processing form promoted differences in ruminal fermentation at 0 and 4 h; however, 8 h after feeding R cereals resulted in higher rumen pH (6·17v.5·71) and lower concentration of lactic acid (88·1v.156 mg/l) and volatile fatty acids (only in diet B, 118v.164 mm/l) compared with G. Little effect of dietary factors in the target rumen microorganisms were observed. The more balanced fermentation observed with R cereals may be explained by the lower concentrate intake promoted during the first 4 h, coupled with a more difficult access of bacterial enzymes to their starch, thus reducing its fermentation rate. Therefore, feeding dry-rolled cereals may be useful to reduce the risk of acidosis by regulating the intake pattern of the concentrate and/or its fermentation rate.

Relationships between functional genes in Lactobacillus delbrueckii ssp. bulgaricus isolates and phenotypic characteristics associated with fermentation time and flavor production in yogurt elucidated using multilocus sequence typing

Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) is well known for its worldwide application in yogurt production. Flavor production and acid producing are considered as the most important characteristics for starter culture screening. To our knowledge this is the first study applying functional gene sequence multilocus sequence typing technology to predict the fermentation and flavor-producing characteristics of yogurt-producing bacteria. In the present study, phenotypic characteristics of 35 L. bulgaricus strains were quantified during the fermentation of milk to yogurt and during its subsequent storage; these included fermentation time, acidification rate, pH, titratable acidity, and flavor characteristics (acetaldehyde concentration). Furthermore, multilocus sequence typing analysis of 7 functional genes associated with fermentation time, acid production, and flavor formation was done to elucidate the phylogeny and genetic evolution of the same L. bulgaricus isolates. The results showed that strains significantly differed in fermentation time, acidification rate, and acetaldehyde production. Combining functional gene sequence analysis with phenotypic characteristics demonstrated that groups of strains established using genotype data were consistent with groups identified based on their phenotypic traits. This study has established an efficient and rapid molecular genotyping method to identify strains with good fermentation traits; this has the potential to replace time-consuming conventional methods based on direct measurement of phenotypic traits.

De novo production of six key grape aroma monoterpenes by a geraniol synthase-engineered S. cerevisiae wine strain.

BackgroundMonoterpenes are important contributors to grape and wine aroma. Moreover, certain monoterpenes have been shown to display health benefits with antimicrobial, anti-inflammatory, anticancer or hypotensive properties amongst others. The aim of this study was to construct self-aromatizing wine yeasts to overproduce de novo these plant metabolites in wines.ResultsExpression of the Ocimum basilicum (sweet basil) geraniol synthase (GES) gene in a Saccharomyces cerevisiae wine strain substantially changed the terpene profile of wine produced from a non-aromatic grape variety. Under microvinification conditions, and without compromising other fermentative traits, the recombinant yeast excreted geraniol de novo at an amount (~750 μg/L) well exceeding (>10-fold) its threshold for olfactory perception and also exceeding the quantities present in wines obtained from highly aromatic Muscat grapes. Interestingly, geraniol was further metabolized by yeast enzymes to additional monoterpenes and esters: citronellol, linalool, nerol, citronellyl acetate and geranyl acetate, resulting in a total monoterpene concentration (~1,558 μg/L) 230-fold greater than that of the control. We also found that monoterpene profiles of wines derived from mixed fermentations were found to be determined by the composition of the initial yeast inocula suggesting the feasibility of producing ‘à la carte’ wines having predetermined monoterpene contents.ConclusionsGeraniol synthase-engineered yeasts demonstrate potential in the development of monoterpene enhanced wines.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0306-5) contains supplementary material, which is available to authorized users.

Hybridization within Saccharomyces Genus Results in Homoeostasis and Phenotypic Novelty in Winemaking Conditions.

Despite its biotechnological interest, hybridization, which can result in hybrid vigor, has not commonly been studied or exploited in the yeast genus. From a diallel design including 55 intra- and interspecific hybrids between Saccharomyces cerevisiae and S. uvarum grown at two temperatures in enological conditions, we analyzed as many as 35 fermentation traits with original statistical and modeling tools. We first showed that, depending on the types of trait – kinetics parameters, life-history traits, enological parameters and aromas –, the sources of variation (strain, temperature and strain * temperature effects) differed in a large extent. Then we compared globally three groups of hybrids and their parents at two growth temperatures: intraspecific hybrids S. cerevisiae * S. cerevisiae, intraspecific hybrids S. uvarum * S. uvarum and interspecific hybrids S. cerevisiae * S. uvarum. We found that hybridization could generate multi-trait phenotypes with improved oenological performances and better homeostasis with respect to temperature. These results could explain why interspecific hybridization is so common in natural and domesticated yeast, and open the way to applications for wine-making.

Australian native shrubs: Delivering benefits to livestock, soil, plants and people

s / Journal of Nutrition & Intermediary Metabolism 1 (2014) 1e55 6 marine products, particularlyfishmeal andfish oil, to beingmainly based on terrestrial products. One of the most important on-going strategies for feeding aquaculture is continually refining feeds to ensure they remain sustainable. This is especially the case for intensive aquaculture systems that rely on formulated manufactured aquafeeds. Ingredient screening and development underpin this and sit alongside other strategies to improve animal performance and increase how efficiently feeds are used. Aquaculture has global reach and offers aquaculture systems that are appropriate in different regions depending on environmental, cultural and socio-economic factors. For Atlantic salmon, off-shore and land-based systems are being discussed. Location-specific integrated multi-trophic aquaculture provides one direction with great promise, it also reflects the 3000 year old history of aquaculture that achieved an elegant solution through integrated polyculture. Funding source(s): N/A.

Yearly variation in maize silage fermentation and nutritive quality

AbstractA significant effect of year on maize nutritive value has been reported in many studies; however, the direct effect of year on both nutritive values and fermentation traits of maize silage has not been directly investigated. During a 7‐year period (2006–2012), we investigated the following variables of 597 maize silages commercially produced in bunker silos on farms in the Czech Republic: dry‐matter content (DM), crude protein (CP), starch, amylase‐treated neutral detergent fibre (aNDF), acid detergent fibre (ADF) and net energy lactation (NEL), as well as fermentation traits such as pH, contents of lactic acid (LA), acetic acid (AA), butyric acid (BA) and the ratio between LA and volatile fatty acids. The effect of year and DM explained 16 and 30% of the variability in nutritive and fermentation traits respectively. Although a common silage DM content was used for each year, the climatic effect of year significantly changed almost all tested variables, but particularly aNDF, ADF, starch, AA and BA. The year contribution to trait variability effect was as much as two times higher for fermentation traits (12·6%) as for nutritive value (6·1%). Temperature–precipitation relationships associated with achieved maize yield were considered as factors explaining the year effect. Temperature and precipitation averaged over the full vegetation period had low relevance to nutritive and fermentation traits. This study reveals the importance of year‐to‐year variation in silage nutritive value and fermentation, which could be useful for understanding the contribution of year to these changes in both field experiments and national assessments.

Effect of inclusion of distillers dried grains and solubles from barley, wheat and corn in isonutritive diets on the performance and caecal environment of growing rabbits

To evaluate how the dietary inclusion of distillers dried grains and solubles (DDGS) could affect the performance and caecal environment of growing rabbits, four experimental diets were formulated from a control diet without DDGS (C), including 20% of barley DDGS (Db20), 20% of wheat DDGS (Dw20) and 20 (Dc20) or 40% (Dc40) of corn DDGS. Animals had free access to medicated versions of the diets until 49 d, and then to unmedicated diets until 59 d of age. The performance trial was done using 475 three-way crossbred weaned rabbits of 28 d of age, individually housed in 5 batches. Caecal fermentation traits were determined in 20 animals per diet and at 42 d and at 59 d of age. No significant effect of the growing diet on mortality, morbidity or sanitary risk index was observed. In the whole period and respect to the control group, animals fed with Db20 showed higher dry matter (DM) and digestible energy (DE) intake (+6 and +12%, respectively; P<0.05), but similar daily weight gain (DWG) and increased feed conversion ratio (+9%; P<0.05). Similarly, and regardless of its inclusion level, the increase in DE intake of animals fed with corn DDGS (+9, respectively; P<0.05) did not increase DWG. In contrast, higher DM and DE intake of animals fed with Dw20 (+8; P<0.05) resulted in a higher DWG (+2.8 g/d; P<0.05) than those fed with C. Although inclusion of DDGS at 20% did not affected main caecal parameters controlled at 42 d, caecum of animals fed with the diet Dc40 was characterized by greater N-NH3 and valeric acid and lower total volatile fatty acids and acetic acid concentrations than the average of the other groups (on av. +5.2±1.7 mmol/L, +0.29±0.07 mol/100 mol, –17.17±4.41 μmol/L and –2.60±0.99 mol/100 mol, respectively; P<0.05). At 59 d of age, higher caecal DM, and propionic and valeric acid concentration and lower values of total volatile fatty acids and acetic/propionic rate were observed for DDGS inclusion at 20% compared to the control (+1.6±0.5%, +0.95±0.44 mol/100 mol, –9.3±4.3 μmol/L and –2.7±1.2, respectively; P<0.05). Linear inclusion of corn DDGS increased caecal DM, propionic acid proportion and total volatile fatty acids concentration and reduced acetate/propionic rate (+4.0±0.4%, +2.27±0.41 mol/100 mol, –21.27±3.9 μmol/L and –5.6±1.1, respectively for Dc40 compared to C; P<0.05). Rabbits given Dc40were also characterized for a greater caecum N-NH3 content than the other groups (on av. –8.7±1.7 mmol/L; P<0.05) at 59 d of age. The results of the present work reveal that inclusion of DDGS up to 20%, independently of the grain source (barley, wheat or corn), could be an interesting alternative in balanced diets for growing rabbits.

Phenotypic traits of genetically closely related Leuconostoc spp.

The aim of the study was to evaluate intercluster and intracluster phenotypic and genetic diversity of Leuconostoc spp. PFGE and RAPD-PCR were used to evaluate molecular diversity. Carbohydrate metabolism of the isolates was evaluated using API 50CH. The study demonstrated that genetically closely related isolates will not necessarily demonstrate the same phenotypic relatedness, indicating that phenotypic traits are isolate specific. Therefore, genetic selection of isolates by clustering for further phenotypic characterisation of representatives, might lead to loss of important phenotypic diversity. Furthermore, PFGE was shown to be an efficient molecular tool for the differentiation of Leuconostoc mesenteroides subsp. cremoris and Leuconostoc pseudomesenteroides, that has not been reported previously. Additionally, amygdaline, arbutine, l-arabinose and mannitol can be important fermentation traits for phenotypic differentiation of Ln. mesenteroides subsp. cremoris and Ln. pseudomesenteroides.

Biological effect of tannins from different vegetal origin on microbial and fermentation traits in vitro

The biological effect of tannins (proportion of the response in different parameters when tannins were inactivated with polyethylene glycol, PEG) as an easy, rapid way to estimate the magnitude of their effect on rumen microbial fermentation, was estimated in vitro for the tropical browse legumes Albizia lebbekoides, Acacia cornigera and Leucaena leucocephala, which differ in their phenolic and tannin content. Samples were incubated in rumen fluid for 24 h in four runs. The inactivation by PEG of tannins from A. lebbekoides increased gas production from 1.62- to 2.83-fold, with this biological effect increasing up to 8 h incubation, then being maintained and increasing after 16 h. In A. cornigera and L. leucocephala, the magnitude of the improvement of gas production was lower (from 1.1- to 1.32-fold and from 1.29- to 1.56-fold) and constant. The inclusion of PEG increased total volatile fatty acids (VFA) concentration (P = 0.019), reduced the molar proportion of acetate (P < 0.001) and increased that of butyrate (P < 0.001) and branched-chain VFA (P < 0.001). Microbial protein mass in A. lebbekoides increased with PEG in a higher extent (P < 0.001) than in L. leucocephala, but it was reduced in A. cornigera. No biological effect was observed on the efficiency of microbial protein synthesis when it was related to VFA concentration (P > 0.10), but when related to the gas produced it was lowest with A. lebbekoides (P = 0.023). The biological effect of tannins, either in total extent or along the incubation period differed according to their origin. Irrespective of their amount or chemical nature, the biological effect gives a direct idea of how tannins affect both the extent and pattern of forages fermentation.

Methane emissions, body composition, and rumen fermentation traits of beef heifers differing in residual feed intake1

This study examined the relationship of residual feed intake (RFI) and performance with methane emissions, rumen fermentation, and digestion in beef heifers. Individual DMI and growth performance were measured for 22 Simmental heifers (mean initial BW 449 kg, SD = 46.2 kg) offered grass silage ad libitum for 120 d. Ultrasonically scanned muscle and fat depth, BCS, muscularity score, skeletal measurements, blood variables, rumen fermentation (via stomach tube), and total tract digestibility (indigestible marker) were measured. Methane production was estimated using the sulfur hexafluoride tracer gas technique over two 5-d periods beginning on d 20 and 75 of the RFI measurement period. Phenotypic RFI was calculated as actual DMI minus expected DMI. The residuals of the regression of DMI on ADG and midtest metabolic body weight, using all heifers, were used to compute individual RFI coefficients. Heifers were ranked by RFI and assigned to low (efficient), medium, or high (inefficient) groupings. Overall ADG and DMI were 0.58 kg (SD = 0.18) and 7.40 kg (SD = 0.72), respectively. High-RFI heifers consumed 9 and 15% more (P < 0.05) than medium- and low-RFI groups, respectively. Body weight, growth, skeletal, and composition traits did not differ (P > 0.05) between low- and high-RFI groups. High-RFI heifers had higher concentrations of plasma glucose (6%) and urea (13%) and lower concentrations of plasma creatinine (9%) than low-RFI heifers (P < 0.05). Rumen pH and apparent in vivo digestibility did not differ (P > 0.05) between RFI groups, although acetate:propionate ratio was lowest (P = 0.07) for low-RFI (3.5) and highest for high-RFI (4.6) heifers. Methane production expressed as grams per day or grams per kilogram metabolic body weight was greater (P < 0.05) for high (297 g/d and 2.9 g/kg BW0.75) compared with low (260 g/d and 2.5 g/kg BW0.75) RFI heifers, with medium (275 g/d and 2.7 g/kg BW0.75) RFI heifers being intermediate. Regression analysis indicated that a 1 kg DM/d increase in RFI was associated with a 23 g/d increase (P = 0.09) in methane emissions. Results suggest that improved RFI will reduce methane emissions without affecting productivity of growing beef cattle.

Differential adaptation to multi-stressed conditions of wine fermentation revealed by variations in yeast regulatory networks

BackgroundVariation of gene expression can lead to phenotypic variation and have therefore been assumed to contribute the diversity of wine yeast (Saccharomyces cerevisiae) properties. However, the molecular bases of this variation of gene expression are unknown. We addressed these questions by carrying out an integrated genetical-genomic study in fermentation conditions. We report here quantitative trait loci (QTL) mapping based on expression profiling in a segregating population generated by a cross between a derivative of the popular wine strain EC1118 and the laboratory strain S288c.ResultsMost of the fermentation traits studied appeared to be under multi-allelic control. We mapped five phenotypic QTLs and 1465 expression QTLs. Several expression QTLs overlapped in hotspots. Among the linkages unraveled here, several were associated with metabolic processes essential for wine fermentation such as glucose sensing or nitrogen and vitamin metabolism. Variations affecting the regulation of drug detoxification and export (TPO1, PDR12 or QDR2) were linked to variation in four genes encoding transcription factors (PDR8, WAR1, YRR1 and HAP1). We demonstrated that the allelic variation of WAR1 and TPO1 affected sorbic and octanoic acid resistance, respectively. Moreover, analysis of the transcription factors phylogeny suggests they evolved with a specific adaptation of the strains to wine fermentation conditions. Unexpectedly, we found that the variation of fermentation rates was associated with a partial disomy of chromosome 16. This disomy resulted from the well known 8–16 translocation.ConclusionsThis large data set made it possible to decipher the effects of genetic variation on gene expression during fermentation and certain wine fermentation properties. Our findings shed a new light on the adaptation mechanisms required by yeast to cope with the multiple stresses generated by wine fermentation. In this context, the detoxification and export systems appear to be of particular importance, probably due to nitrogen starvation. Furthermore, we show that the well characterized 8–16 translocation located in SSU1, which is associated with sulfite resistance, can lead to a partial chromosomic amplification in the progeny of strains that carry it, greatly improving fermentation kinetics. This amplification has been detected among other wine yeasts.