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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.