Metabolic Modeling and Bidirectional Culturing of Two Gut Microbes Reveal Cross-Feeding Interactions and Protective Effects on Intestinal Cells.

The gut microbiota is constituted by thousands of microbial interactions, some of which correspond to the exchange of metabolic by-products or cross-feeding. Inulin and xylan are two major dietary polysaccharides that are fermented by members of the human gut microbiota, resulting in different metabolic profiles. Here, we integrated community modeling and bidirectional culturing assays to study the metabolic interactions between two gut microbes, Phocaeicola dorei and Lachnoclostridium symbiosum, growing in inulin or xylan, and how they provide a protective effect in cultured cells. P. dorei (previously belonging to the Bacteroides genus) was able to consume inulin and xylan, while L. symposium only used certain inulin fractions to produce butyrate as a major end product. Constrained-based flux simulations of refined genome-scale metabolic models of both microbes predicted high lactate and succinate cross-feeding fluxes between P. dorei and L. symbiosum when growing in each fiber. Bidirectional culture assays in both substrates revealed that L. symbiosum growth increased in the presence of P. dorei. Carbohydrate consumption analyses showed a faster carbohydrate consumption in cocultures compared to monocultures. Lactate and succinate concentrations in bidirectional cocultures were lower than in monocultures, pointing to cross-feeding as initially suggested by the model. Butyrate concentrations were similar across all conditions. Finally, supernatants from both bacteria cultured in xylan in bioreactors significantly reduced tumor necrosis factor-α-induced inflammation in HT-29 cells and exerted a protective effect against the TcdB toxin in Caco-2 epithelial cells. Surprisingly, this effect was not observed in inulin cocultures. Overall, these results highlight the predictive value of metabolic models integrated with microbial culture assays for probing microbial interactions in the gut microbiota. They also provide an example of how metabolic exchange could lead to potential beneficial effects in the host. IMPORTANCE Microbial interactions represent the inner connections in the gut microbiome. By integrating mathematical modeling tools and microbial bidirectional culturing, we determined how two gut commensals engage in the exchange of cross-feeding metabolites, lactate and succinate, for increased growth in two fibers. These interactions underpinned butyrate production in cocultures, resulting in a significant reduction in cellular inflammation and protection against microbial toxins when applied to cellular models.

Enzymatic synthesis optimization of isoamyl butyrate from fusel oil

Many food, cosmetic and pharmaceutical industries have increased their interest in short-chain esters due to their flavor properties. From the industrial standpoint, enzyme reactions are the most economical strategy to reach green products with neither toxicity nor damage to human health. Isoamyl butyrate (pear flavor) was synthesized by isoamyl alcohol (a byproduct of alcohol production) and butyric acid with the use of the immobilized lipase Lipozyme TL IM and hexane as solvents. Reaction variables (temperature, butyric acid concentration, isoamyl alcohol:butyric acid molar ratio and enzyme concentration) were investigated in ester conversion (%), concentration (mol L-1) and productivity (mmol ester g-1 mixture . h), by applying a sequential strategy of the Fractional Factorial Design (FFD) and the Central Composite Rotatable Design (CCRD). High isoamyl butyrate conversion of 95.8% was achieved at 24 hours. At 3 hours, the highest isoamyl butyrate concentration (1.64 mol L-1) and productivity (0.19 mmol ester g-1 mixture . h) were obtained under different reaction conditions. Due to high specificity and selectivity of lipases, process parameters of this study and their interaction with the Lipozyme TL IM are fundamental to understand and optimize the system so as to achieve maximum yield to scale up. Results show that fusel oil may be recycled by the green chemistry process proposed by this study.(AU)

Enzymatic synthesis optimization of isoamyl butyrate from fusel oil

Many food, cosmetic and pharmaceutical industries have increased their interest in short-chain esters due to their flavor properties. From the industrial standpoint, enzyme reactions are the most economical strategy to reach green products with neither toxicity nor damage to human health. Isoamyl butyrate (pear flavor) was synthesized by isoamyl alcohol (a byproduct of alcohol production) and butyric acid with the use of the immobilized lipase Lipozyme TL IM and hexane as solvents. Reaction variables (temperature, butyric acid concentration, isoamyl alcohol:butyric acid molar ratio and enzyme concentration) were investigated in ester conversion (%), concentration (mol L-1) and productivity (mmol ester g-1 mixture . h), by applying a sequential strategy of the Fractional Factorial Design (FFD) and the Central Composite Rotatable Design (CCRD). High isoamyl butyrate conversion of 95.8% was achieved at 24 hours. At 3 hours, the highest isoamyl butyrate concentration (1.64 mol L-1) and productivity (0.19 mmol ester g-1 mixture . h) were obtained under different reaction conditions. Due to high specificity and selectivity of lipases, process parameters of this study and their interaction with the Lipozyme TL IM are fundamental to understand and optimize the system so as to achieve maximum yield to scale up. Results show that fusel oil may be recycled by the green chemistry process proposed by this study.

Anti-inflammatory effect of microbial consortia during the utilization of dietary polysaccharides.

The gut microbiome has a significant impact on host health, especially at the metabolic level. Dietary compounds arriving at the colon have a large influence on the composition of the gut microbiome. High fiber diets have been associated to health benefits that are mediated in great part by short chain fatty acids (SCFA). Gut microbial interactions are relevant for the utilization of complex carbohydrates in the gut microbiome. In this work we characterized the utilization of two dietary polysaccharides by combinations of representative adult gut microbes, and the impact of their activities on a cellular inflammation model. Paired combinations of Bifidobacterium adolescentis, Bacteroides dorei, Lactobacillus plantarum, Escherichia coli and Clostridium symbiosum were grown in inulin or xylan as carbon source. Their relative abundance, substrate consumption and major SCFAs produced were determined. Higher cell growth was observed during inulin consumption, and B. adolescentis and L. plantarum were dominant in co-cultures. The co-culture of B. dorei and C. symbiosum was dominant in xylan. In several cases the combined bacterial growth was lower in co-cultures than monocultures, with a few exceptions of synergistic growth between microorganisms. Inulin fermentation resulted in larger acetate and lactate concentrations, and several combinations grown in xylan containing C. symbiosum were characterized by high amounts of butyrate. These microbial consortia were scaled to batch bioreactor fermentations reaching high cell densities and similar profiles to co-culture experiments. Interestingly, a microbial combination producing high amounts of butyrate was able to reduce IL-8 expression in HT-29 cells co-incubated with TNFα. In summary, this work shows that microbial interactions during the utilization of dietary polysaccharides are complex and substrate dependent. Moreover, certain combinations deploy potent anti-inflammatory effects, which are independent of individual microbial growth, and could be mediated in part by higher butyrate production.

Caracterização do efeito anti-neoplásico do butirato em duas linhagens celulares de rato derivadas de tumores hepáticos com diferente ní­vel de diferenciação / Characterization of the anti-neoplastic effect of butyrate in two mouse cell lines derived from hepatic tumors with different levels of differentiation

O carcinoma hepatocelular (HCC) é uma neoplasia primária com mau prognóstico e alta taxa de recorrência. Estudos recentes demostram que o HCC pode ser classificado em três subtipos segundo o perfil molecular. Destes subtipos, o HCC pouco diferenciado apresenta pior prognostico. Neste sentido, torna-se de particular interesse o estudo de compostos com efeitos diferenciadores e citotóxicos nas células destas neoplasias pouco diferenciadas. O butirato, um ácido graxo de cadeia curta produzido pela fermentação microbiana da fibra alimentar no intestino, tem demonstrado atividade anti-neoplásica e capacidade moduladora da diferenciação celular em diversos tipos celulares, incluindo linhagens de HCC humano e células progenitoras hepáticas. Assim, objetivou-se neste estudo, caracterizar o efeito do butirato de sódio (NaBu) em duas linhagens de células neoplásicas de rato: uma pouco diferenciada (GP7TB) e a outra, uma linhagem derivada de um HCC diferenciado (JM-1). A linhagem GP7TB mostrou maior resistência ao NaBu (ED50= 7,7 mM) do que as células JM-1 (ED50= 5,2 mM). A redução na viabilidade celular após 72 h de tratamento com NaBu esteve relacionada com a diminuição na proliferação celular e no caso das células GP7TB, de um aumento na apoptose. O tratamento com NaBu induziu alterações morfológicas nas duas linhagens celulares, porém apenas nas células do tipo GP7TB, essas alterações sugerem um processo de diferenciação/transdiferenciação celular. O aumento na expressão de genes envolvidos no controle da pluripotência de células tronco, assim como de alguns marcadores de células tronco, sugere que o NaBu induziu uma reprogramação profunda das células GP7TB. Por outro lado, a redução na expressão de genes relacionados com migração e plasticidade celular assim como de proliferação celular apontam que estas células diminuíram seu potencial invasivo e a capacidade de autorenovação. Embora sejam necessárias análises adicionais para confirmar o efeito observado nos perfis de expressão gênica, os resultados deste estudo sugerem que o NaBu apresenta efeito antineoplásico por meio da redução da proliferação, aumento da apoptose e modulação da expressão de genes associados com a transição epitéliomesenquimal em células com características tronco tumorais

Hepatocellular carcinoma (HCC) is a primary neoplasia with poor prognosis and high recurrence rate. Recent evidence suggests that HCC can be classified in three different subtypes based on their molecular profile. Among these subtypes, the poorlydifferentiated HCC has the worst prognosis. Therefore, the study of compounds with pro-differentiating and cytotoxic effects on poorly-differentiated neoplastic cells represents a matter of primary concern. Butyrate which is a short-chain fatty acid produced by microbial fermentation in the intestine, has demonstrated anti-neoplastic activity and pro-differentiating potential in several cell types, including, human HCC cell lines and liver progenitor cells. In this study, we aimed to characterize the effect of sodium butyrate (NaBu) on two neoplastic cell lines derived from rats: a poorlydifferentiated cell line (GP7TB) and, a cell line derived from a well-differentiated HCC. GP7TB showed increased resistance to NaBu treatment (ED50= 7.7 mM) compared to JM-1 (ED50= 5.2 mM). The reduction in cell viability observed after 72 h of treatment was explained by a reduction in cell proliferation and, in the case of GP7TB, by increased levels of apoptosis. The NaBu treatment induced morphological alterations in both cell lines. However, only in the case of GP7TB cells, the alterations suggested a differentiation/transdifferentiation process. The up-regulation of genes involved in pluripotency and genes expressing stem cell markers indicated that NaBu triggered a deep reprogramming of GP7TB cells. Besides, a down-regulation in the expression of genes related with cell migration and plasticity suggested that these cells reduced their invasive potential and their self-renewal capacity. Additional analyses are necessary to confirm the observed effect on gene expression profiles. However, the results of this study suggest that NaBu exert anti-neoplastic effects through apoptosis, reduction of cell proliferation and downregulation of genes associated with epithelial-mesenchymal transition of cancer stem-like cells

Effects of volatile fatty acids in biohydrogen effluent on biohythane production from palm oil mill effluent under thermophilic condition

Background: Biohydrogen effluent contains a high concentration of volatile fatty acid (VFA) mainly as butyric, acetic, lactic and propionic acids. The presence of various VFAs (mixture VFAs) and their cooperative effects on two-stage biohythane production need to be further studied. The effect of VFA concentrations in biohydrogen effluent of palm oil mill effluent (POME) on methane yield in methane stage of biohythane production was investigated. Results: The methane yield obtained in low VFA loading (0.9 and 1.8 g/L) was 15­20% times greater than that of high VFA loading (3.6 and 4.7 g/L). Butyric acid at high concentrations (8 g/L) has the individual significantly negative effect the methane production process (P b 0.05). Lactic, acetic and butyric acid mixed with propionic acid at a concentration higher than 0.5 g/L has an interaction significantly negative effect on the methanogenesis process (P b 0.05). Inhibition condition had a negative effect on both bacteria and archaea with inhibited on Geobacillus sp., Thermoanaerobacterium thermosaccharolyticum, Methanoculleus thermophilus and Methanothermobacter delfuvii resulting in low methane yield. Conclusion: Preventing the high concentration of butyric acid, and propionic acid in the hydrogenic effluent could enhance methane production in two-stage anaerobic digestion for biohythane production.

Key odor and physicochemical characteristics of raw and roasted jicaro seeds (Crescentia alata K.H.B.).

Jicaro seeds (Crescentia alata) are widely consumed in Central America, primarily as a popular tasty and nutritious beverage called "horchata". Seeds are roasted to develop a specific aroma through a process that has never been explored. Volatile compounds, extracted from raw and roasted jicaro seeds (140°C for 140s) by SAFE (Solvent Assisted Flavor Evaporation), were analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). Twenty-seven volatile compounds were isolated, among which, ethyl-2-methylbutyrate was designated by olfactometry as providing the characteristic jicaro note (0.16 and 0.47mg/kg dry basis (d.b.) in raw and roasted seeds, respectively). The release of volatile compounds from the Maillard reaction, such as pyrazines, and the increase of ethyl-2-methylbutyrate after roasting, exhausted the pleasant jicaro aroma. This mild roasting process had a slight impact on polyphenol, fructose and free amino acid contents, in agreement with the Maillard reaction. Confocal microscopy showed the coalescence of lipids in roasted jicaro seeds, which might explain the higher extracted fat content.

Chemical Studies of Yellow Tamarillo (Solanum betaceum Cav.) Fruit Flavor by Using a Molecular Sensory Approach.

The odor-active volatile compounds of yellow tamarillo fruit (S. betaceum Cav.) were identified and quantified by using a sensomics approach, combining a gentle volatile extraction (solvent-assisted flavor evaporation (SAFE)), gas chromatography-mass spectrometry (GC-MS), and sensory analyses (gas chromatography-olfactometry (GC-O) and aroma extract dilution analysis (AEDA)). The medium-term purpose of this work is to evaluate the change of odor-active volatiles during processing. Thus, (Z)-3-hexenal, hexanal, and ethyl butanoate were identified as key aroma compounds of yellow tamarillo. The C6-aliphatic compounds, aliphatic esters, and terpenols were characterized as the volatiles responsible for the herbal-green, fruity, and fresh-mint odor notes of this variety, respectively. Additionally, one non-volatile compound contributing to the residual bitter taste of this fruit was isolated by a bioguided (taste sensory analyses) fractionation. The freeze-dried fruit was sequentially liquid-liquid partitioned with solvents of different polarity, and then the ethyl acetate fraction was submitted to size exclusion chromatography. Then, its structure was elucidated as rosmarinic acid, by using common spectroscopic methods (mass spectrometry (MS) and nuclear magnetic resonance (NMR)). The amount of rosmarinic acid was quantified as 46.17 ± 1.20 mg/100 g of dried fruit, by the external standard method. Its bitter taste threshold value was determined by using the 3AFC (alternative forced choice) method to be 37.00 ± 1.25 mg/L.

Dietary supplementation with probiotic and butyrate for Litopenaeus vannamei in pre-nursery / Suplementação dietética com probiótico e butirato de sódio no pré-berçário de Litopenaeus vannamei

This study aimed to evaluate the diet supplementation with sodium butyrate, probiotic (Lactobacillus plantarum) and their interaction, in the diet for post-larvae of the Pacific white shrimp (Litopenaeus vannamei) in pre-nursery. We used the following treatments during the entire experimental period: (1) Probiotic 1x108 UFC/g, sodium butyrate 2%, (3) probiotic 1x108 UFC/g + sodium butyrate 2%, (4) control (Base diet). In all treatment we added culture medium in the same doses as in the probiotic treatments. We used 16 experimental units of 60L each, with the bottom Ushaped, stocked with 2,880 post-larvae 5. Fifteen days later, regardless the presence or absence of the probiotic, shrimps from treatment with butyrate had higher survival (p = 0.0039) and lowest individual dry weight (p = 0.0043). No morphological changes were observed in the gut of postlarvae in any treatment. Therefore, the diet supplementation with sodium butyrate increases the survival of shrimp post-larvae of in the pre-nursery phase, without causing morphological changes in its gut.

Este estudo teve por objetivo avaliar o uso suplementar de probiótico (Lactobacillus plantarum) e butirato de sódio, e a interação deles na dieta de póslarvas de camarão-branco-do-pacífico (Litopenaeus vannamei) em fase de pré-berçário. Durante o experimento foram aplicados nas dietas os tratamentos: (1) probiótico 1x108 UFC/g, (2) butirato de sódio 2%, (3) probiótico 1x108 UFC/g + butirato de sódio 2%, (4) controle (dieta base). Todos os tratamentos tiveram a adição de meio de cultura na mesma dosagem utilizada nos tratamentos com probiótico. Foram utilizadas 16 unidades experimentais de 60 L cada uma, com fundo em formato U, povoadas com 2.880 póslarvas 5. Após quinze dias, independentemente da presença ou não do probiótico, os camarões dos tratamentos com butirato apresentaram maior sobrevivência (p = 0,0039) e menor peso seco individual (p = 0,0043). Não foram observadas alterações morfológicas no intestino das pós-larvas em nenhum dos tratamentos. Portanto, a suplementação com butirato de sódio na ração aumenta a sobrevivência das pós-larvas de camarões na fase de pré-berçário sem causar alteração morfológica em seu intestino.

Dietary supplementation with probiotic and butyrate for Litopenaeus vannamei in pre-nursery / Suplementação dietética com probiótico e butirato de sódio no pré-berçário de Litopenaeus vannamei

This study aimed to evaluate the diet supplementation with sodium butyrate, probiotic (Lactobacillus plantarum) and their interaction, in the diet for post-larvae of the Pacific white shrimp (Litopenaeus vannamei) in pre-nursery. We used the following treatments during the entire experimental period: (1) Probiotic 1x108 UFC/g, sodium butyrate 2%, (3) probiotic 1x108 UFC/g + sodium butyrate 2%, (4) control (Base diet). In all treatment we added culture medium in the same doses as in the probiotic treatments. We used 16 experimental units of 60L each, with the bottom Ushaped, stocked with 2,880 post-larvae 5. Fifteen days later, regardless the presence or absence of the probiotic, shrimps from treatment with butyrate had higher survival (p = 0.0039) and lowest individual dry weight (p = 0.0043). No morphological changes were observed in the gut of postlarvae in any treatment. Therefore, the diet supplementation with sodium butyrate increases the survival of shrimp post-larvae of in the pre-nursery phase, without causing morphological changes in its gut.(AU)

Este estudo teve por objetivo avaliar o uso suplementar de probiótico (Lactobacillus plantarum) e butirato de sódio, e a interação deles na dieta de póslarvas de camarão-branco-do-pacífico (Litopenaeus vannamei) em fase de pré-berçário. Durante o experimento foram aplicados nas dietas os tratamentos: (1) probiótico 1x108 UFC/g, (2) butirato de sódio 2%, (3) probiótico 1x108 UFC/g + butirato de sódio 2%, (4) controle (dieta base). Todos os tratamentos tiveram a adição de meio de cultura na mesma dosagem utilizada nos tratamentos com probiótico. Foram utilizadas 16 unidades experimentais de 60 L cada uma, com fundo em formato U, povoadas com 2.880 póslarvas 5. Após quinze dias, independentemente da presença ou não do probiótico, os camarões dos tratamentos com butirato apresentaram maior sobrevivência (p = 0,0039) e menor peso seco individual (p = 0,0043). Não foram observadas alterações morfológicas no intestino das pós-larvas em nenhum dos tratamentos. Portanto, a suplementação com butirato de sódio na ração aumenta a sobrevivência das pós-larvas de camarões na fase de pré-berçário sem causar alteração morfológica em seu intestino.(AU)

Suppressive effect of short-chain fatty acids on production of proinflammatory mediators by neutrophils

Short chain fatty acids (SCFAs) are fermentation products of anaerobic bacteria. More than just being an important energy source for intestinal epithelial cells, these compounds are modulators of leukocyte function and potential targets for the development of new drugs. The aim of this study was to evaluate the effectsof SCFAs (acetate, propionate and butyrate) on production of nitric oxide (NO) and proinflammatory cytokines [tumor necrosis factor á (TNF-á) and cytokineinduced neutrophil chemoattractant-2 (CINC-2áâ)] by rat neutrophils. The involvement of nuclear factor êB (NF-êB) and histone deacetylase (HDAC) wasexamined. The effect of butyrate was also investigated in vivo after oral administration of tributyrin (a pro-drug of butyrate). Propionate and butyrate diminished TNF-á, CINC-2áâ and NO production by LPS-stimulated neutrophils. We also observed that these fatty acids inhibit HDAC activity and NF-êB activation, which might be involved in the attenuation of the LPS response. Products of cyclooxygenase and 5-lipoxygenase are not involved in the effects of SCFAs as indicated by the results obtained with the inhibitors of these enzymes. The recruitment of neutrophils to the peritonium after intraperitoneal administration of a glycogen solution (1%) and the ex vivo production of cytokines and NO by neutrophils were attenuated in rats that previously received tributyrin. These results argue that this triglyceride may be effective in the treatment of inflammatory conditions.

Composition and chemopreventive effect of polysaccharides from common beans (Phaseolus vulgaris L.) on azoxymethane-induced colon cancer.

Common beans ( Phaseolus vulgaris L.) contain a high proportion of undigested carbohydrates (NDC) that can be fermented in the large intestine to produce short-chain fatty acids (SCFA) such as acetate, propionate, and butyrate. The objective of the present study was to evaluate the composition and chemopreventive effect of a polysaccharide extract (PE) from cooked common beans ( P. vulgaris L) cv. Negro 8025 on azoxymethane (AOM) induced colon cancer in rats. The PE induced SCFA production with the highest butyrate concentrated in the cecum zone: 6.7 +/- 0.06 mmol/g of sample for PE treatment and 5.29 +/- 0.24 mmol/g of sample for PE + AOM treatment. The number of aberrant crypt foci (ACF) and the transcriptional expression of bax and caspase-3 were increased, and rb expression was decreased. The data suggest that PE decreased ACF and had an influence on the expression of genes involved in colon cancer for the action of butyrate concentration.

Characterization of volatile compounds of Mezcal, an ethnic alcoholic beverage obtained from Agave salmiana.

Commercial mezcals (white, white with worm, rested, rested with worm, and aged) produced from Agave salmiana were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). Thirty-seven compounds were identified, and nine of them were classified as major compounds of mezcal (MCM). Saturated alcohols, ethyl acetate, ethyl 2-hydroxypropanoate, and acetic acid form the MCM group. Minor compounds of mezcal group include other alcohols, aldehydes, ketones, large chain ethyl esters, organic acids, furans, terpenes, alkenes, and alkynes. Most of the compounds found in mezcals in this study are similar to those present in tequilas and other alcoholic beverages. However, mezcals contain unique compounds such as limonene and pentyl butanoate, which can be used as markers for the authenticity of mezcal produced from A. salmiana.

Characterization of cachaça and rum aroma.

Cachaça, the most popular alcoholic beverage in Brazil, is a sugar cane spirit similar to rum. Its production is around 2 billion liters per year, of which <1% is exported. Although rum is similar to cachaça its flavor difference is easily recognizable. Using gas chromatography-olfactometry (GCO) to separate and characterize the odorants present in cachaça and rum, these two sugar cane products were compared and standards identified to use in a descriptive sensory analysis (DSA). In the DSA cachaça was more intense in the grassy, spicy, sulfury, and vinegar descriptors, whereas apple and caramel were the same in both rum and cachaça. The GCO data for the apple-smelling compounds beta-damascenone along with ethyl butyrate, isobutyrate, and 2-methylbutyrate were at the same potency in both cachaça and rum, whereas the spicy-smelling eugenol, 4-ethylguaiacol, and 2,4-nonadienal were much more potent in cachaça.

[Influence of sodium butyrate intake on murine colonic carcinogenesis]. / Influencia de la ingesta de butirato de sodio en la carcinogénesis colónica murina.

The role of short chain fatty acids (SCFA) in murine colonic carcinogenesis (MCC) has not yet been clarified. In rats, Freeman et al have reported an increased number of colonic tumors induced with dimethylhydrazine (DMH) and sodium butyrate in drinking water. On the other hand, Deschner et al showed that tributyrin intake did not increase MCC induced with azoxymethane. Both of them have reported high levels of fecal butyric acid with sodium butyrate and tributyrin intake. Although salt intake has been positively associated with colorectal cancer some authors do not support this association. We have evaluated the influence of right hemicolectomy (RH) (right colon as main source of SCFA) and the intake of 2%-pH 7 sodium butyrate (S.BUT) and 4 g/l sodium chloride (S.CHL) in drinking water, in MCC. Forty eight male Wistar rats weighing 150 g were divided into 4 groups: RH, S.BUT, S.CHL, control (C). Half of the animals received weekly DMH 20 mg/kg subcutaneously for 12 weeks. Necropsy was performed after 6 months. We have determined fecal SCFA content by gas chromatography. Neoplasm was present in 70% of rats treated with DMH. The number of animals with tumors was: RH 4/6, S.BUT 4/6, S.CHL 3/5, C 6/6. Tumor frequency was: RH 1.17 +/- 0.48, S.BUT 1.50 +/- 0.76, S.CHL 1.20 +/- 0.49, C 1.50 +/- 0.22. S.BUT group, treated with DMH, presented a lower butyric acid concentration (p < 0.05) in comparison with other groups. We have no explanation for this finding; gastric absorption of sodium butyrate may be an important factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Volatile fatty acids, lactic acid, and pH in the stools of breast-fed and bottle-fed infants.

We measured fecal pH, volatile fatty acids (VFA), and lactic acid concentrations in 67 healthy infants ranging in age from 1 to 5 months. The babies were divided into five groups according to their diet: group 1: human milk, with subgroups of 1 month of age (n = 8), and 2-5 months (n = 12); group 2: formula milk, with subgroups of 1 month of age (n = 9) and 2-5 months (n = 10); group 3: cow's milk, one group of 2-5 months of age (n = 12); group 4: human milk supplemented with formula milk, 2-5 months of age (n = 8); and group 5: human milk supplemented with cow's milk, 2-5 months of age (n = 8). Fecal VFA concentration and pH of bottle-fed infants (groups 2 and 3) were significantly higher and lactic acid concentrations significantly lower than those of the breast-fed group. Groups 4 and 5 showed significantly higher pH and propionic acid concentration, and lower lactic acid concentration than Group 1 did. There were no significant differences in the data on pH, VFA, and lactic acid concentrations between the feces of formula and cow's milk groups. On the other hand, the addition of formula or cow's milk to the human milk was sufficient to alter the profile of VFA, the pH, and the lactic acid concentration of breast-fed infants stools. Low pH, low VFA, and high lactic acid concentrations make the colonic content of breast-fed babies an environment favorable for Bifidobacteria growth, and this is probably the main protective factor against gastrointestinal infections.

[Biochemistry of the evolutive cycle of Triatoma infestans (vinchuca). V. Volatile fatty acids emission]. / Bioquimica del ciclo evolutivo del Triatoma infestans (vinchuca). V. Emision de acidos grasos volatiles.

The composition of the volatile fatty acids emitted by Triatoma infestans of both sexes was studied. They were constituted by a mixture of the acids acetic, propionic, butyric, isobutyric, isovaleric, valeric and traces of isohexanoic and octanoic. Acetic acid was predominant followed by isobutyric and then by propionic acid. The other fatty acids are minor constituents. When acetic acid was discounted, the remaining composition was similar to the volatile fatty acid distribution pattern of Brindley gland. Both sexes showed a similar composition and therefore discard the possibility that they may function as sexual pheromones.