Screening of live yeast and yeast derivatives for their impact of strain and dose on in vitro ruminal fermentation and microbial profiles with varying media pH levels in high-forage beef cattle diet.

BACKGROUND: Yeast products showed beneficial effects with respect to stabilizing ruminal pH, stimulating ruminal fermentation and improving production efficiency. Batch cultures were conducted to evaluate the effects of yeast products on gas production (GP), dry matter disappearance (DMD) and fermentation characteristics of high-forage substrate. The study was a two media pH (5.8 and 6.5) × five yeasts (three live yeasts, LY: LY1, LY2, LY3; two yeast derivatives, YD: YD4, YD5) × four dosages factorial arrangement, with monensin (Mon) assigned as a positive control. RESULTS: Greater (P < 0.01) GP, DMD, volatile fatty acid (VFA) concentration, ratio of acetate to propionate (A:P) and copy numbers of Fibrobacter succinogenes and Ruminococcus flavefaciens were observed at pH 6.5 than at pH 5.8. The GP kinetics, DMD, VFA concentration, A:P and NH3 -N concentration differed (P < 0.05) among yeasts but varied with media pH or yeast dosages. Increasing doses of LY3 linearly increased DMD (P < 0.04) and VFA concentration (P < 0.001) at media pH 5.8. The DMD linearly (P < 0.02) increased with increased addition of YD4 (pH 6.5) and YD5 (pH 5.8) and the ratio of A:P linearly decreased (P < 0.01) with the addition of YD4 or YD5 at pH 5.8. Overall greater (P < 0.05) GP, A:P (pH 5.8) and DMD (pH 6.5) were observed with yeast products than with Mon. CONCLUSION: LY3 appeared to be an interesting candidate for improving rumen digestibility and fermentation efficiency, particularly at low media pH. YD4 or YD5 improved fermentation efficiency and can be potentially fed as an alternative to Mon. © 2019 Her Majesty the Queen in Right of Canada Journal of the Science of Food and Agriculture © 2019 Society of Chemical Industry.

Differing effects of 2 active dried yeast (Saccharomyces cerevisiae) strains on ruminal acidosis and methane production in nonlactating dairy cows.

Fifteen ruminally cannulated, nonlactating Holstein cows were used to measure the effects of 2 strains of Saccharomyces cerevisiae, fed as active dried yeasts, on ruminal pH and fermentation and enteric methane (CH(4)) emissions. Nonlactating cows were blocked by total duration (h) that their ruminal pH was below 5.8 during a 6-d pre-experimental period. Within each block, cows were randomly assigned to control (no yeast), yeast strain 1 (Levucell SC), or yeast strain 2 (a novel strain selected for enhanced in vitro fiber degradation), with both strains (Lallemand Animal Nutrition, Montréal, QC, Canada) providing 1 × 10(10) cfu/head per day. Cows were fed once daily a total mixed ration consisting of a 50:50 forage to concentrate ratio (dry matter basis). The yeast strains were dosed via the rumen cannula daily at the time of feeding. During the 35-d experiment, ruminal pH was measured continuously for 7 d (d 22 to 28) by using an indwelling system, and CH(4) gas was measured for 4 d (d 32 to 35) using the sulfur hexafluoride tracer gas technique (with halters and yokes). Rumen contents were sampled on 2 d (d 22 and 26) at 0, 3, and 6h after feeding. Dry matter intake, body weight, and apparent total-tract digestibility of nutrients were not affected by yeast feeding. Strain 2 decreased the average daily minimum (5.35 vs. 5.65 or 5.66), mean (5.98 vs. 6.24 or 6.34), and maximum ruminal pH (6.71 vs. 6.86 or 6.86), and prolonged the time that ruminal pH was below 5.8 (7.5 vs. 3.3 or 1.0 h/d) compared with the control or strain 1, respectively. The molar percentage of acetate was lower and that of propionate was greater in the ruminal fluid of cows receiving strain 2 compared with cows receiving no yeast or strain 1. Enteric CH(4) production adjusted for intake of dry matter or gross energy, however, did not differ between either yeast strain compared with the control but it tended to be reduced by 10% when strain 2 was compared with strain 1. The study shows that different strains of S. cerevisiae fed as active dried yeasts vary in their ability to modify the rumen fermentative pattern in nonlactating dairy cows. Because strain 2 tended (when compared with strain 1) to lower CH(4) emissions but increase the risk of acidosis, it may be prudent to further evaluate this strain in cattle fed high-forage diets, for which the risk of acidosis is low but CH(4) emissions are high.

Identification and characterization of lactic acid bacteria and yeasts of PDO Tuscan bread sourdough by culture dependent and independent methods.

Sourdough fermentation has been increasingly used worldwide, in accordance with the demand of consumers for tasty, natural and healthy food. The high diversity of lactic acid bacteria (LAB) and yeast species, detected in sourdoughs all over the world, may affect nutritional, organoleptic and technological traits of leavened baked goods. A wide regional variety of traditional sourdough breads, over 200 types, has been recorded in Italy, including special types selected as worthy of either Protected Geographical Indication (PGI) or Protected Designation of Origin (PDO), whose sourdough microbiota has been functionally and molecularly characterized. As, due to the very recent designation, the microbiota of Tuscan bread sourdough has not been investigated so far, the aim of the present work was to isolate and characterize the species composition of LAB and yeasts of PDO Tuscan bread sourdough by culture-independent and dependent methods. A total of 130 yeasts from WLN medium and 193 LAB from both mMRS and SDB media were isolated and maintained to constitute the germplasm bank of PDO Tuscan bread. Ninety six LAB from mMRS medium and 68 yeasts from WLN medium were randomly selected and molecularly identified by ARDRA (Amplified Ribosomal DNA Restriction Analysis) and PCR-RFLP analysis of the ITS region, respectively, and sequencing. The yeast identity was confirmed by 26S D1/D2 sequencing. All bacterial isolates showed 99% identity with Lactobacillus sanfranciscensis, 65 yeast isolates were identified as Candida milleri, and 3 as Saccharomyces cerevisiae. Molecular characterization of PDO Tuscan bread sourdough by PCR-DGGE confirmed such data. The distinctive tripartite species association, detected as the microbiota characterizing the sourdough used to produce PDO Tuscan bread, encompassed a large number of L. sanfranciscensis and C. milleri strains, along with a few of S. cerevisiae. The relative composition and specific physiological characteristics of such microbiota could potentially affect the nutritional features of PDO Tuscan bread, as suggested by the qualitative functional characterization of the isolates. Investigations on the differential functional traits of such LAB and yeast isolates could lead to the selection of the most effective single strains and of the best performing strain combinations to be used as starters for the production of baked goods.

Evaluation of different genetic procedures for the generation of artificial hybrids in Saccharomyces genus for winemaking.

Several methods based on recombinant DNA techniques have been proposed for yeast strain improvement; however, the most relevant oenological traits depend on a multitude of loci, making these techniques difficult to apply. In this way, hybridization techniques involving two complete genomes became interesting. Natural hybrid strains between different Saccharomyces species have been detected in diverse fermented beverages including wine, cider and beer. These hybrids seem to be better adapted to fluctuating situations typically observed in fermentations due to the acquisition of particular physiological properties of both parental strains. In this work we evaluated the usefulness of three different hybridization methods: spore to spore mating, rare-mating and protoplast fusion for the generation of intra- and inter-specific stable hybrids, being the first report about the comparison of different methods to obtain artificial hybrids to be used in fermentations. Spore to spore mating is an easy but time-consuming method; hybrids generated with this technique could lack some of the industrially relevant traits present in the parental strains because of the segregation occurred during meiosis and spore generation prior to hybridization. Hybrids obtained by protoplast fusion get the complete information of both parents but they are currently considered as genetically modified organisms (GMOs). Finally, hybrids obtained by rare-mating are easily obtained by the optimized methodology described in this work, they originally contain a complete set of chromosomes of both parents and they are not considered as GMOs. Hybrids obtained by means of the three methodological approaches showed a high genetic variability; however, a loss of genetic material was detected in most of them. Based on these results, it became evident that a last crucial aspect to be considered in every hybridization program is the genetic stabilization of recently generated hybrids that guarantee its invariability during future industrial utilization. In this work, a wine yeast genetic stabilization process was developed and vegetatively stable hybrids were obtained.

Utilización de Candida guilliermondii aislada del corozo chiquito (Bactris guineensis) en la producción de xilitol / Utilization of Candida guilliermondii isolated of corozo chiquito (Bactris guineensis) in the production of xylitol

La levadura Candida guilliermondii es objeto de estudio debido a su capacidad de producir xilitol aprovechando compuestos hemicelulósicos ricos en xilosa, dado esto, la cepa Candida guilliermondii aislada del fruto del corozo chiquito (Bactris guineensis) fue usada en este estudio con el fin de evaluar su capacidad para producir xilitol sobre un sustrato hidrolizado de cascarilla de arroz. El objetivo de este trabajo fue determinar los parámetros fermentativos como producción de xilitol, productividad volumétrica (Qp) y rendimiento de sustrato en producto (Yp/s) durante la fermentación con la cepa nativa Candida guilliermondii. Se emplearon 200 ml de medio de cultivo hidrolizado de cascarilla de arroz, el cual contenía una concentración de xilosa de 27,5 g/L. La fermentación se llevó a cabo bajo las siguientes condiciones: temperatura 30 ºC, pH del medio 5,8, agitación 120 rpm e inóculo adaptado de 3 g/L. Los resultados mostraron que después de 120 horas de fermentación se obtuvieron 2,6 g/L de xilitol con productividad volumétrica (Qp) de 0,02 g/L-h y rendimiento de sustrato en producto (Yp/s) de 0,13 g/g. De esta manera, la cepa nativa Candida guilliermondii, aislada del fruto de Corozo chiquito (Bactris guineensis), produjo xilitol bajo condiciones específicas de fermentación.

The yeast Candida guilliermondii has been studied due to its ability to produce xylitol in xylose-rich hemicellulosic compounds, Candida guilliermondii strain isolated from the fruit of Corozo chiquito (Bactris guineensis) was used in this study to assess their ability to xylitol production on these substrates. The aim of this study was to determine the fermentation parameters such as xylitol production, volumetric productivity (Qp) and yield of xylitol production (Yp/s) during fermentation with the native strain Candida guilliermondii. Was used 200 ml of culture medium rice husk hydrolysate, which contained a xylose concentration of 27.5 g/L. The fermentation was carried out under the following conditions: temperature 30 ºC, pH of 5.8, agitation 120 rpm and adapted inoculum of 3 g/L. The results showed that after 120 hours of fermentation 2.6 g / L of xylitol was achieved with volumetric productivity (Qp) 0.02 g/L-h and 0.13 g/g yield of xylitol production (Yp/s). The native strain Candida guilliermondii, isolated from the fruit of Corozo chiquito (Bactris guineensis) produced xylitol fermentation under specific conditions.