Metabólitos e genes do catabolismo de lactose e de proteínas envolvidos na formação de flavor em Lactobacillus delbrueckii UFV H2b20

• Autor(a) principal: Carmo, Ana Paula do
• 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/123456789/1553
• topic: Lactobacillus delbrueckii UFV H2b20; Flavor compounds; Lactobacillus delbrueckii UFV H2b20; Flavor compounds; Lactose catabolism; Protein catabolism; Probiotics; CNPQ::CIENCIAS BIOLOGICAS::MICROBIOLOGIA::MICROBIOLOGIA APLICADA

The identification of specific genes involved in flavor-forming pathways is a basic requirement for the prediction of the potential use of lactic acid bacteria (LAB) in the dairy industry. The aim of this study was to identify metabolites and genes involved in flavor formation in the probiotic strain Lactobacillus delbrueckii UFV H2b20. Phylogenetic trees analyses with genes encoding a lactate dehydrogenase, ldh, and also the catabolic control protein A (CcpA), ccpA-pepR1, strengthen the classification of this probiotic strain in NCFM group, as proposed by a comparative genomics study of Lactobacillus. The Bayesian inference analysis for adhE gene, encoding an acetaldehyde dehydrogenase, presented an evolutionary pattern closer to that of probiotic L. acidophilus NCFM, corroborating the suggestion that this strain might be considered as a new and unusual subspecies among L. delbrueckii subspecies, the first one identified as a probiotic. Eight genes belonging to this system were identified in the L. delbrueckii UFV H2b20 genome, which possess a closely phylogenetic relationship to NCFM strains representative, as it was demonstrated for oppC e oppBII, encoding oligopeptide transport system components. PepC, PepN, and PepX might be essential for growth of LAB, probiotic or not, since the correspondent genes are always present, including in L. delbrueckii UFV H2b20 genome. For pepX gene, a probable link between carbohydrate catabolism and PepX expression may exists, where it is regulated by PepR1/CcpA-like, a common feature between Lactobacillus strains and also in L. delbrueckii UFV H2b20. The well conserved evolutionary history of the ilvE gene is evidence that the pathways leading to branched-chain amino acid degradation, such as isoleucine and valine, are similar among L. delbrueckii subsp. bulgaricus strains and L. delbrueckii UFV H2b20. Thus, the involvement of succinate in flavor formation can be attributed to IlvE activity. The presence of aminopeptidase G in L. delbrueckii UFV H2b20 genome, which is absent in several strains, might improve the proteolytic activity and effectiveness. The nucleotide sequence encoding PepG revealed that it is a cysteine endopeptidase, belonging to Peptidase_C1superfamily; sequence analysis showed 99 % identity with L. delbrueckii subsp. bulgaricus ATCC 11842 pepG, whereas protein sequence analysis revealed 100 % similarity with PepG from the same organism. The present study proposes a schematic model to explain how does the proteolytic system of L. delbrueckii UFV H2b20 works, based on the components identified until the present date.