Monday, August 11, 2008
P10

Effect of phenolic compounds on the growth of Ustilago maydis in submerged culture

Maribel Cornejo-Mazón, M. Eugenia Jaramillo, Lourdes Villa-Tanaca, and Humberto Hernández-Sánchez. Dept. Graduados e Investigación en Alimentos, Escuela Nacional de Ciencias Biológicas - Instituto Politécnico Nacional, Carpio y Plan de Ayala, Col. Sto. Tomás, Mexico, DF, 11340, Mexico

The phytopatogenic and dimorphic fungus Ustilago maydis is the causal agent of the corn smut disease. However, this microorganism has also been grown in submerged culture to produce different useful metabolites such as lysine, glycolipids and several enzymes (proteases, nucleases, lipases). The growth of this fungus in the presence of phenolic compounds could indicate the possible presence of other kind on enzymes. In this work, U. maydis FB1, FB2 and FBD12 were grown in submerged cultured in baffled Erlenmeyer flasks using YPD broth as a basal medium in the presence of 0.05 g/L of a natural (ferulic acid) or a synthetic (2,5-xylidine) phenolic compound. The fermentations were carried out at 32ºC on a rotary orbital shaker at 200 rpm for 48 h. The medium was filtered and the biomass dried to constant weight at 65ºC. In the case of YPD broth without phenolic compounds, the biomass concentrations were 7.9, 10.9 and 11.1 g/L for strains FB1, FB2 and FBD12 respectively. The addition of 2,5-xylidine to the broth inhibited strongly the growth of the strain FB1 which reached only a final biomass concentration of 5.5 g/L while the other two strains were not affected. Ferulic acid was the strongest growth inhibitor, since final biomass concentrations of just 2.0, 0.8 and 1.2 for FB1, FB2 and FBD12 were obtained. Laccases usually prefer 2,5-xylidine over ferulic acid as substrates, so it is possible that this kind of oxidative enzymes are present in U. maydis.


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