Cinética de crescimento, características bioquímico-morfológicas de envelhecimento e perfil metabólico de culturas contínuas de Kluyveromyces lactis sob limitação por nitrogênio

• Autor(a) principal: Correa, Lygia Fátima da Mata
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1556
• topic: Cinética de crescimento; Envelhecimento; Perfil metabólico; Kluyveromyces lactis; Limitação por nitrogênio; Growth kinetics; Aging; Metabolic profile; Kluyveromyces lactis; Nitrogen limitation; CNPQ::CIENCIAS BIOLOGICAS::MICROBIOLOGIA::MICROBIOLOGIA APLICADA::MICROBIOLOGIA INDUSTRIAL E DE FERMENTACAO

In order to investigate aging of Kluyveromyces lactis continuous cultures under nitrogen nutritional limitation, to the identification of extracellular signals that trigger this process or in response to limiting conditions of the medium, K. lactis cultures were physiologically characterized under different levels of nitrogen limitation. Physiological growth and nitrogen limitation conditions for K. lactis continuous cultures were established in YCB supplemented with ammonium sulfate (μmax. = 0.40 h-1 and Ks = 0.091 mM) buffered with phosphate buffer (pH 5.5 - 6.0 ) and with flux which resulted in growth rates of 0.01 to 0.2 h-1, corresponding to nitrogen limitation. Under the lowest growth rates, K. lactis cultures in steady state showed greater generation time, residence time, biomass and extracellular protein. In addition, populations of cells in K. lactis cultures under the lowest growth rates showed lower viability, higher bud scars percentage, higher N-acetylglucosamine concentration, greater ROS accumulation, higher percentage of apoptosis by phosphatidylserine externalization and DNA fragmentation, larger celullar dimension, higher production of tryptophol, phenylethanol and lower production of ethanol and glycerol. These data suggest that K. lactis continuous cultures operated at low growth rates could be suitable for studying the physiology of aging in yeasts. The extracellular metabolic profiling of K. lactis cultures revealed 19 fragments of different metabolites. At lower growth rates, the fragments 299, 321, 349, 485, 507, 543, 583 and 756 were less abundant while the fragments 432, 656 and 714 were more abundant. The hierarchical clustering of the fragments comprised five groups consisting of different fragments (m/z) and the clustering of treatments allowed to obtaining three groups. However, it was not possible to make the fragments correlation of the metabolites detected with the K. lactis cellular aging or with the nitrogen limitation condition in itself, since the identification of these extracellular metabolites was not completed. For GC-MS xiv were identified 28 extracellular metabolites (amino acids, organic acids and fatty acids) secreted by K. lactis cultures. Some metabolites were differentially more abundant in lower growth rates while others were more abundant in higher growth rates. Different metabolic pathways were related to the production of extracellular metabolites identified, but a detailed analysis should be done to correlate them with possible extracellular signals that trigger the aging process or that may be involved with the limiting conditions of the medium.