INVESTIGADORES
SANGORRIN marcela paula
congresos y reuniones científicas
Título:
Actividad antagónica de levaduras killer frente a hongos del género Aspergillus sección nigri
Autor/es:
MARQUINA-LUÉVANO,I.; SANGORRIN, M.P.; ELIZONDO-ZERTUCHE, M.; ROBLEDO LEAL, E.
Lugar:
Guanajato
Reunión:
Congreso; III Congreso Internacional sobre Innovación y Tendencias en Procesamiento de Alimentos y XVIII C. Nac. de Ciencia y Tecnología de Alimentos; 2016
Resumen:
Cryptococcus victoriae NPCC 1263, with antagonistic properties against fungal pathogens of postharvest pear fruits, was selected in a previous work carried out in our laboratory. For selection assays a not optimized medium (NOM, 12.2% v/v molasses, 1 g/L urea, 20°C) was employed. The objective of this work was to optimize the biomass production of the selected yeast in a laboratory scale bioreactor.Experimental Design using a molasses-based medium was employed for the optimization. Variables including molasses, urea and phosphate concentration as well as temperature were identified to show significant influence on the biomass production, and they were used to perform a Central Composite Experimental Design. Three levels were used for each parameter: molasses (% v/v: 2.1, 4.2, 6.4), KH2PO4 (% w/v: 0, 0.1, 0.05), urea (g/L: 1; 1.4; 1.8) and temperature (°C: 4, 8; 13), and a total of 18 run conditions (combinations) were performed. Cultures were performed in 250 ml Erlenmeyer flasks with 100 ml culture media. As a result of this analysis, a predominant influence of temperature in the yeast growth was observed. Three run conditions showing the highest biomass production were selected: C7, C9 and C15. Cells obtained from these conditions and the NOM were evaluated in their biocontrol capacity in order to know if culture conditions could affect this activity. Similarly, other physiological features were also analyzed in these cells including production of glucanases, proteases, pectinases, chitinases and killer toxins at 0°C and 20°C, H2O2 resistance (10 mM for 1h) as well as the effect of different conservation temperature (-20°C, 4°C and 20°C) and protectants (water, sorbitol and trehalose) on yeast viability. No differences were find in the hydrolytic enzymes and killer toxin production assays for cells from each different culture conditions. The highest percentages of viability were obtained in cells from C7 and C9 media containing sorbitol as cryopreservative at the three temperatures evaluated. Finally, resistance to H2O2 (indicative of stress resistance of cells) was higher for cells from C7 medium. According to these results, C7 medium (6.4% v/v molasses, 0.1% w/v KH2PO4, 1 g/L urea) was selected to perform 20L cultures. Growth curves obtained in the bioreactor were fitted using the Gompertz modified model and parameters Maximum growth (A) and Maximum growth rate (μ) were obtained for C. victoriae growing in C7 and NOM media. Values obtained for A and μ were 2.49 and 0.08 h-1 in C7 medium, and of 2.33 and 0.06 h-1 in NOM medium, evidencing an improvement in culture parameters with optimized medium.Summarizing, optimized culture conditions obtained at Erlenmeyer scale were reproduced at a larger scale, producing cells with stable biocontrol related properties