An industrial profile of yeast production

This profile provides a brief introduction to the yeast production industry with particular emphasis on the production of baker's yeast. Yeast can be obtained either as the primary product of a process, as in the case of baker's yeast, or as a secondary or by-product from alcoholic fermentations. Secondary yeast is usually preferred to primary yeast for use as animal feed for reasons of economy. Carbohydrates in the form of molasses or hydrolysed starches are the most commonly used substrates for yeast growth. Carbohydrate-containing waste streams from other processes and n-paraffins from oil have also been exploited for the production of feed yeast. Processes for the production of primary yeast vary but basically consist of materials preparation, seed yeast production, fermentation, yeast separation and pressing or drying steps, depending on the type of yeast required. About half a million tonnes are thought to be produced annually, slightly under half as baker's yeast. The size of plant can vary from half a tonne per day upwards. Plants have been built for n-paraffin feed yeast with capacities of 100,000 tonnes per year. The cost of a basic plant to produce 7.5 tonnes of active dried baker's yeast (10% moisture) per day would be about £3.5 million f.o.b. UK in July 1980. Additional plant, necessary in many locations, would increase the cost. Yeast plants are not labour intensive; this scale of operation would provide 21-24 jobs. Detailed feasibility studies should be undertaken to follow up this introduction where it is felt circumstances might be favourable

Utilisation de souches de levures génétiquement modifiées en œnologie

ENOSAFE (No. 762, Programa AGRO, medida 8).Fundação para a Ciência e a Tecnologia (FCT), l’Instituto Nacional de Investigação Agrária et LeVin - POCI/AGR/56102/2004

Live yeast as a possible modulator of polyunsaturated fatty acid biohydrogenation in the rumen

In dairy cows, several studies focused on the effects of sodium bicarbonate and fibre on ruminal linoleic acid (c9c12-C18:2) biohydrogenation (BH) whereas literature is scarce about the effect of live yeast, used as a feed additive. The objective of this in vivo study was to evaluate the capacity of two dietary feed additives, sodium bicarbonate and live yeast (Strain Sc47), and hay to modulate ruminal BH and particularly conjugated linoleic acids (CLA) and trans-monoenoic acids (t-C18:1) production. Four dry dairy cows fitted with ruminal cannula, were used in a 4×4 Latin square design. They were given a control diet (CD) at a daily feeding rate of 10.4 kg of dry matter/cow supplemented with 100 g/d of sodium bicarbonate or 5 g/d of live yeast or a hay diet formulated to provide the same main fatty acids (FA) as CD during a 14-d experimental period. Ruminal pH and redox potential were measured from 1 h before feeding to 8 h after, and ruminal fluid samples were taken at 5 h after feeding for volatile fatty acids, ammonia and fatty acid determination. In addition to the in vivo experiment, an in vitro experiment was carried out to ascertain the possible mode of action of live yeast on c9c12-C18:2 BH: ruminal fluid was obtained from a donor cow fed with hay and was incubated in batch cultures over 6 h with a 6-pH buffer using starch, urea and grape seed oil as substrates. Results gathered from both experiments suggested that live yeast supplement increased the accumulation of t-C18:1 compared to sodium bicarbonate and prevented the formation of C18:0 which is usually observed when hay is added to a high concentrate diet. The accumulation of t-C18:1 observed in presence of live yeast was probably due to an inhibition of the second reduction step as a result of a more complete isomerisation of c9c12-C18:2

Valorisation de la biodiversité des levures dans la zone Océan indien (Réunion, Madagascar). Le cas du métabolisme des arômes chez la levure Saprochaete suaveolens, isolée du fruit du pitahaya

International audienceno abstrac

Optimisation de systèmes de piégeage vis-à-vis des mouches des fruits (Diptera : Tephritidae) économiquement importantes de l'île de la Réunion

A la Réunion, les mouches de fruits (Diptera: Tephritidae) constituent les principaux ravageurs des cultures fruitières et légumières. Dans le cadre de la lutte biotechnique, le laboratoire d'Entomologie du CIRAD-FLHOR Réunion travaille sur la mise au point de systèmes de piégeage vis-à-vis des deux sexes (et particulièrement des femelles) des Tephritidae importantes à la Réunion. Pour cela on compare deux séries de systèmes de piégeage, «série 1» et «série 2» sur trois mouches des fruits: Ceratitis rosa («série 1»), Neoceratitis cyanescens («série 1») et Bactrocera cucurbitae («série 2»). La comparaison des systèmes de piégeage de la «série 1» permet de confirmer l'efficacité et la spécificité du "3-lures"® vis-à-vis des femelles de Ceratitis rosa. En ce qui concerne Neoceratitis cyanescens, les faibles captures ne nous permettent pas de discuter et de comparer l'attractivité de cette série de systèmes de piégeage. La comparaison des systèmes de piégeage de la «série 2» met en valeur l'ammonium acétate pour son attractivité sélective (respect des auxiliaires et nettoyage plus rapide du piège) envers Bactrocera cucurbitae et son conditionnement sous forme de diffuseur (maniement pratique et action à long terme). Du point de vue de la lutte biotechnique, ces résultats confirment les avancées qui ont été réalisées sur les Ceratitis spp.. De plus, pour Bactrocera cucurbitae même si les systèmes de piégeage ne permettent pas encore en l'état d'envisager une telle lutte, les résultats de cette étude serviront dans un premier temps à optimiser de futurs essais en lutte raisonnée puis en lutte biotechnique sur cette espèce. (Résumé d'auteur