RESUMO
Generally, the selection of fructans prebiotics and probiotics for the formulation of a symbiotic has been based on arbitrary considerations and in vitro tests that fail to take into account competitiveness and other interactions with autochthonous members of the intestinal microbiota. However, such analyzes may be a valuable step in the development of the symbiotic. The present study, therefore, aims to investigate the effect of lactobacilli strains and fructans (prebiotic compounds) on the growth of the intestinal competitor Klebsiella oxytoca, and to assess the correlation with short-chain fatty acids production. The short-chain fatty acids formed in the fermentation of the probiotic/prebiotic combination were investigated using NMR spectroscopy, and the inhibitory activities were assessed by agar diffusion and co-culture methods. The results showed that Lactobacillus strains can inhibit K. oxytoca, and that this antagonism is influenced by the fructans source and probably associated with organic acid production.
Assuntos
Ácidos Graxos Voláteis/metabolismo , Frutanos/análise , Klebsiella oxytoca/fisiologia , Espectroscopia de Ressonância Magnética/métodos , Prebióticos/análise , Probióticos/análise , Fermentação/fisiologia , Microbioma Gastrointestinal/fisiologia , Trato Gastrointestinal/metabolismo , Trato Gastrointestinal/microbiologia , Klebsiella oxytoca/ultraestrutura , Lactobacillus acidophilus/fisiologia , Lactobacillus acidophilus/ultraestrutura , Microscopia Eletrônica de VarreduraRESUMO
Agave fructans are increasingly important in food industry and nutrition sciences as a potential ingredient of functional food, thus practical analysis tools to characterize them are needed. In view of the importance of the molecular weight on the functional properties of agave fructans, this study has the purpose to optimize a method to determine their molecular weight distribution by HPLC-SEC for industrial application. The optimization was carried out using a simplex method. The optimum conditions obtained were at column temperature of 61.7°C using tri-distilled water without salt, adjusted pH of 5.4 and a flow rate of 0.36mL/min. The exclusion range is from 1 to 49 of polymerization degree (180-7966Da). This proposed method represents an accurate and fast alternative to standard methods involving multiple-detection or hydrolysis of fructans. The industrial applications of this technique might be for quality control, study of fractionation processes and determination of purity.
Assuntos
Agave , Cromatografia Líquida de Alta Pressão , Cromatografia em Gel , Frutanos , Peso MolecularRESUMO
Fructan-type inulin and fructo-oligosaccharides (FOS) are reserve polysaccharides that offer an interesting combination of nutritional and technological properties for food industry. Stevia rebaudiana is used commercially in the sweetener industry due to the high content of steviol glycosides in its leaves. With the proposal of using industrial waste, the objective of the present study was to isolate, characterize and evaluate the prebiotic activity of inulin and FOS from S. rebaudiana stems. The chemical characterization of the samples by GC-MS, NMR and off-line ESI-MS showed that it was possible to obtain inulin molecules from the S. rebaudiana stems with a degree of polymerization (DP) of 12, and FOS with a DP<6. The in vitro prebiotic assay of these molecules indicates a strain specificity in fermentation capacity of fructans as substrate. FOS molecules with a low DP are preferably fermented by beneficial microbiota than inulin molecules with higher DP.
Assuntos
Fermentação , Resíduos Industriais/análise , Inulina/química , Microbiota , Stevia/química , Configuração de Carboidratos , Inulina/metabolismoRESUMO
Stevia rebaudiana (Bertoni) is widely studied because of its foliar steviol glycosides. Fructan-type polysaccharides were recently isolated from its roots. Fructans are reserve carbohydrates that have important positive health effects and technological applications in the food industry. The objective of the present study was to isolate and characterize fructo-oligosaccharides (FOSs) from S. rebaudiana roots and in vitro adventitious root cultures and evaluate the potential prebiotic effect of these molecules. The in vitro adventitious root cultures were obtained using a roller bottle system. Chemical analyses (gas chromatography-mass spectrometry, (1)H nuclear magnetic resonance, and off-line electrospray ionization-mass spectrometry) revealed similar chemical properties of FOSs that were obtained from the different sources. The potential prebiotic effects of FOSs that were isolated from S. rebaudiana roots enhanced the growth of both bifidobacteria and lactobacilli, with strains specificity in their fermentation ability.
Assuntos
Oligossacarídeos/biossíntese , Células Vegetais/metabolismo , Raízes de Plantas/metabolismo , Prebióticos , Stevia/metabolismo , Raízes de Plantas/citologia , Stevia/citologiaRESUMO
This study combined physical data from synchrotron SAXS, FTIR and microscopy with in-silico molecular structure predictions and mathematical modeling to examine inulin adjuvant particle formation and structure. The results show that inulin polymer chains adopt swollen random coil in solution. As precipitation occurs from solution, interactions between the glucose end group of one chain and a fructose group of an adjacent chain help drive organized assembly, initially forming inulin ribbons with helical organization of the chains orthogonal to the long-axis of the ribbon. Subsequent aggregation of the ribbons results in the layered semicrystalline particles previously shown to act as potent vaccine adjuvants. γ-Inulin adjuvant particles consist of crystalline layers 8.5 nm thick comprising helically organized inulin chains orthogonal to the plane of the layer. These crystalline layers alternate with amorphous layers 2.4 nm thick, to give overall particle crystallinity of 78%.
Assuntos
Adjuvantes Imunológicos/química , Inulina/química , Configuração de Carboidratos , Simulação por Computador , Microscopia Eletrônica de Transmissão , Simulação de Dinâmica Molecular , Espalhamento a Baixo Ângulo , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios XRESUMO
Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts.