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Articles by M.A. Calvo
Total Records ( 5 ) for M.A. Calvo
  M.A. Calvo , E. Angulo , P. Costa-Batllori , C. Shiva , C. Adelantado and A. Vicente
  Two trials were carried out to study how a compound formed by natural extracts from Rutaceae plants, cinnamon oil and organic acids (RUTEX® PG) could have an effect on intestinal microorganisms on piglets. To obtain this synergistically combination first of all natural extracts and organic acids were separated individually to see its inhibitory action on bacterial growth in vitro. Secondly, the aim was to search the best natural extract and organic acid combination between all the possible ones. RUTEX® PG was the combination that was used in vivo trials with piglets. To study RUTEX® PG effects on piglets two trials were designed. The trials consisted in a comparison between the effect of adding RUTEX® PG to the feed on the intestinal microorganisms of piglets and the effect of antibiotics in feed. The in vitro experiments results showed a synergistic effect of the Rutaceae plant extract and the organic acids tested (citric, formic, lactic and propionic) against different microorganisms: growth inhibition was observed for the organic acid-natural extract combination, while the same concentrations did not show any inhibition when the products were tested separately. Inhibitory activity for cinnamon oil was not tested, because it was added in a very low concentration just to confer an aromatic effect. It was observed, as well, lower bacterial counts at the intestinal segments (duodenum, jejunum, ileum and colon) in comparison with the negative control group. The conclusion is that we can say RUTEX® PG can be active all along the gastro-intestinal segments.
  C. Adelantado , J. Codina , I. Gonzalez , J. Ll. Marti , R. Martinez and M.A. Calvo
  The implication of some bacteria and fungi in alterations in containers and metallic substrata are described in this study and SEM pictures are also provided to check which kind of microorganisms produce alterations in samples collected from pipes, metallic containers intended for water pipes, purifiers and industrial mushroom production. Among the most commonly found microorganisms we may cite Sphaerotilus sp., Galionella sp., Desulfotomaculum sp., Pseudomonas sp., Bacillus sp., Micrococcus luteus, Paecilomyces sp., Aspergillus niger, Aspergillus sp. and Cladosporium sp.
  C. Adelantado , C. Shiva , L. Arosemena , P. Costa-Batllori and M.A. Calvo
  Rutaceae extracts enzymatic activities were studied in order to find out their possible relation with the antimicrobial activity that they possess as well as the improvement of other productive aspects. Several enzymatic activities were detected (Acid phosphatase, alkaline phosphatase, esterase, lipase, leucine arylamidase, trypsine, valine arylamidase, cystine arylamidase, α-fhymotrypsine, naphtol-AS-BI-phosphohydrolase, α-fucosidase, α and β galactosidase, β-glucuronidase, α and β glucosidase, α-mannosidase and N-acetyl-β-glucosaminidase) and special attention is paid to those enzymes that have direct effect on either the bacterial cell structure or the bacterial metabolism.
  S. Figueroa , S. Centeno , M.A. Calvo , A. Rengel and C. Adelantado
  The main objective of this study was to evaluate the frequency distribution of mycobiota and the concentration of Ochratoxin A (OTA) in 50 samples from one company of commercial brand poultry feed produced in Venezuela. The concentration of OTA in the samples analyzed was determined using the competitive ELISA method. The most frequently isolated genera of moulds were Aspergillus (36%) and Penicillium (20%). Of these genera, the most frequently isolated species were Aspergillus flavus, Aspergillus terreus and Penicillium citrinum. Ochratoxigenic species such as Eurotium herbariorum, Aspergillus niger, Aspergillus ochraceus and Aspergillus glaucus, were also found with lower frequency. Rhodotorula mucilaginosa was the only yeast isolated. 94% of the samples presented contamination by OTA in a range between 2.558 and 31.978 μg kg-1 feed and 42% of them presented OTA levels from 10 up to 20 μg kg-1. The findings of this investigation show that 84% of the samples of concentrated feed for meat poultry surpass the maximum permitted limit for OTA of 5 μg kg-1, established in the majority of countries in which regulations are placed.
  S. Centeno , M.A. Calvo , C. Adelantado and S. Figueroa
  The antifungal activity of ethanolic extracts of Rosmarinus officinalis and Thymus vulgaris were tested against strains of Aspergillus flavus and A. ochraceus, since these two species are common contaminants of cereals and grains and are able to produce and accumulate mycotoxins. The methodology used is based on measuring the inhibition halos produced by discs impregnated with the extracts and establishing their Minimum Inhibitory Concentration (MIC) as well as the Minimum Fungicide Concentration (MFC). The results obtained suggest that the assayed extracts affect the proper development of A. flavus and A. ochraceus; leading to a lower MIC (1200 ppm) and MFC (2400 ppm) for T. vulgaris extract against A. ochraceus than against A. flavus. The results show, that the extracts of Rosmarinus officinalis and Thymus vulgaris used at low concentrations could have significant potential for the biological control of fungi in foodstuffs.
 
 
 
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