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Moulds and yeasts are frequently referred as microbial contaminants of feed meals used in intensive animal production. Most of the sanitary risks that are present in milk, eggs and meat are related with the safety of animal feeds. In this study, 75 samples of swine feed, being 10 feed meals and 65 granulated, were tested for mycological characterisation, using conventional methods (NP-3277-2; 2002). Only two granulated feed were negative (2.7%). Out of 75 samples, 73 (97.3%) were positive. Mean count of fungi has been 6.6 × 10² cfu/g ranging from 2.7 × 10¹ to 2.7 × 10³ cfu/g; yeasts were present in 69.9% of the positive samples. Potential toxigenic moulds (Fusarium spp., Aspergillus flavus and Penicillium spp.) were present in all the positive samples with mean levels of 3.2 log₁₀ cfu/g, 2.8 log₁₀ cfu/g and 3.0 log₁₀ cfu/g, respectively. Other genera found were Phoma, Rhizopus and Paecillomyces, with low levels of contamination (32.9%, 35.6% and 47.9%, respectively). It was concluded that the levels and frequency of mycobiota contamination are decreasing judging the results obtained in the last ten years, in Portugal.

An important aspect to consider in the modulation of gene expression with biotechnological purposes is mRNA stability. The KlCYC1 gene has a long (1.2 kb) 3′-UTR region that can be used to modulate gene expression in yeast by the alternative use of its proximal or distal 3′-Untranslated Region [1, 2]. The stability of the two KlCYC1 transcripts was analysed in Saccharomyces cerevisiae puf3 and rpb1-1 mutants. When the puf3 mutant and the deletion of the UGUR element at positions (131-135) were combined, there was a two-fold increase in total KlCYC1 levels mainly due to the increase in the long transcript signal. After a cease of transcription (rpb1-1 mutant), the long transcript was stable for more than two hours while the short one for less than one. When the gene was expressed in the yeast Kluyveromyces lactis under hypoxic conditions, both transcripts were degraded faster than in the rpb1-1 mutant. These findings suggest the presence of different mRNA turnover mechanisms able to operate on KlCYC1 transcripts under different physiological conditions.

The gene HIS4 from Kluyveromyces lactis is transcriptionally activated in complete synthetic respect to rich media and in an independent mechanism related to carbon source. This regulation was not previously described for Saccharomyces cerevisiae HIS4. The EMSA assay carried out with F7 showed a specific band, Fc1, in YPG, and two bands, Fc2 and Fc3, in complete medium. The Fc2 and Fc3 bands were dependent on the carbon source present in the medium, since their intensities were higher in glycerol than in glucose. The protein or proteins causing the Fc1 band seem to be involved in the different regulation mechanisms between rich and synthetic complete media because the Fc1 band was detected in cells grown in synthetic medium. Therefore, the promoter region (-200 to -173) is responsible for two independent regulatory mechanisms.

Yeasts are present throughout the spontaneous fermentation of table olives, and can have a great influence on the final product. For this reason, yeasts could be used as starter cultures in order to improve the quality of table olives. The aim of the present work was to study the effect of the growth conditions on the behaviour of yeast isolated from table olives. In this study, 17 yeast strains obtained from table olives, and belonging to various species of the Candida, Debaryomyces, Kluyveromyces, Pichia and Saccharomyces genera, were characterized by their behaviour in different culture conditions (NaCl and pH). Moreover, the flocculation capacity was studied, and interactions between yeasts and lactic acid bacteria were analyzed. Significant differences were found when yeasts were grown in culture media with salt concentrations between 7% and 12%, and pH between 3.5 and 7. Most of the yeasts analyzed could be useful as starter cultures to enhance the control of table olive fermentation, and hence obtain a high quality final product.

The effect was studied of several yeast strains of the genera Saccharomyces, Pichia, and Kluyveromyces on the persistence of four pesticides (pyraclostrobin, dimethoate, oxamyl, and pymetrozine) in brine during the fermentation process of vegetable products. The growth of yeast strains in a synthetic brine in the presence of the pesticides was recorded with a Bioscreen C kinetic growth reader and compared with their growth in a control brine without pesticides. After incubation for 7 days with the yeast strains, the concentration of pesticides in the synthetic brine was determined. Prior to this pesticide assay, the brines were centrifuged to removing the yeast pellets. The pesticides were determined in both yeast-free brine and yeast pellets and compared with the control consisting of sterile brine with pesticides. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was used to extract the pesticides, which were assayed by LC-MS. The effect of the yeasts on the concentration of the four pesticides in synthetic brine depended on the yeast strain, and was clearest on pymetrozine and pyraclostrobin.

This paper present the Tropical Culture Collection CCT to show how it is and the areas it is involved: Applied microbiology, Culture and preservation methods, Environmental protection, Industrial microbiology, Fermentation, Freeze drying and so on, and also about the services and training courses it offers: Management of a culture collection, Culture and preservation methods, Propagation, Preservation, Storage services (Bacteria, Yeasts, Fungi), Distribution (Bacteria, Yeasts, Fungi).

The new Saccharomyces cerevisiae killer toxin (Klus) killed all the previously known S. cerevisiae killer strains, in addition to other yeast species. The Klus phenotype is encoded by a medium-size dsRNA virus, ScV-Mlus, whose genome size ranged from 2.1 to 2.3 kb. Its genome structure is similar to those of M1, M2, or M28 dsRNAs with a 5’ terminal coding region followed by two internal A-rich sequences and a 3’ terminal region without coding capacity. Mlus positive strands carry cis acting signals at their 5’ and 3’ termini for transcription and replication similar to those of killer viruses. The ORF at the 5’ portion codes for a putative preprotoxin with an N-terminal secretion signal, potential Kex2p/Kexlp processing sites and N-glycosylation sites. No sequence homology was found either between the Mlus dsRNA and M1, M2, or M28 dsRNAs, or between Klus and K1, K2, or K28 toxins. The Klus amino acid sequence showed a significant degree of conservation with the host chromosomally-encoded ORF YFR020W of unknown function.

Among the four types of Saccharomyces killer yeasts already described (K1, K2, K28, and Klus), we found K2 and Klus killer yeasts in south-western Spain. The K2 yeasts were found in all the wine producing sub-areas during all the vintages analyzed, while the Klus yeasts were found in the warmest locations and mostly in the warmest vintages. The killer yeasts were present in most spontaneous fermentations. Most were K2 with Klus being the minority. The proportion of killer yeasts increased during fermentation, while the proportion of sensitive yeasts decreased. The fermentation speed, malic acid, ethanol yield, and wine organoleptic quality decreased in those fermentations where the killer yeasts replaced at least 15% of a dominant population of sensitive yeasts.