Identification of bacterial strains able to produce CLNA isomers for a possible application in the elaboration of new functional food products

• Autor(a) principal: Fontes, Ana Luiza Rodrigues
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.14/20130
• topic: Domínio/Área Científica::Ciências Agrárias::Biotecnologia Agrária e Alimentar

Functional food products consist of a modified foodstuff that can provide additional health and well-being benefits beyond their basic nutrition. In vitro and in vivo studies have reported that conjugated linolenic acid (CLNA) exerts anti-inflammatory, anti-cancer, anti-obesity and antioxidant activities. This group of conjugated isomers is naturally present in vegetable oils and ruminant meat and milk fat, however, lactobacilli, bifidobacteria and propionibacteria strains have revealed the capacity to produce CLNA isomers. Thus, the aim of this work was to identify CLNA producing strains, among a total of 12 Lactobacillus and 3 Bifidobacterium strains, that could be applied in the future formulation of new functional food products. CLA and CLNA microbial producing ability have been related to the presence of the linoleate isomerase (LAI) gene. Therefore, after the optimization of bacterial growth conditions, it was performed a molecular detection assay of LAI gene in Lactobacillus strains. Lactobacillus brevis D24, Lactobacillus plantarum D36 and Lactobacillus plantarum 299v revealed a positive result for the presence of LAI gene. In order to test strains for their CLNA producing ability, selected strains were first tested for their capacity to produce CLA isomers given previous evidence, experimental knowledge and chemical similarity with CLNA group of isomers. Low concentrations of CLA were detected, even for the positive LAI gene strains, although LA reduction rate was considerably high. Two strategies were then applied in order to optimize CLA production: addition of LA to the pre-inocula and inocula and addition of LA after 7 h of incubation. Despite the efforts, CLA production continued to be low in comparison to the percentages of LA reduction. LA was detected in strains’ pellet fatty acid composition, suggesting that the substrate could be being incorporated in the membrane. The amount of LA absorbed did not correspond to the level of substrate that was reduced, therefore, it was concluded that LA must have been converted into other unexpected compounds through an alternative transformation pathway not yet described. Among the strains tested, B. breve NCIMB 702258 was the only strain to demonstrate CLA-producing capacity. Further assays showed that this strain was also able to convert -LNA into CLNA isomers, even in a food matrix (1.6% reduced-fat milk). Therefore, B. breve NCIMB 702258 has the potential to be applied in the elaboration of CLA and CLNA enriched products, however, the organoleptic characteristics will need to be optimized.