Investigating the potential of different dietary fibers to stimulate butyrate production in vitro
Abstract: The project aimed to evaluate the potential of dietary fiber types to stimulate butyrate production using an in vitro system simulating the gut of pigs. Fecal inoculum from suckling piglets were collected in two different periods and were used as inoculum to ferment ß-glucan, inulin and sucrose in two separated in vitro fermentation trials. Gas production profiles, pH, and short chain fatty acids (SCFAs) were measured from samples collected from the in vitro reactors. In addition qPCR were used in an attempt to quantify butyrate producing bacteria. Samples were taken at 6 and 24h for in vitro trial I, and 0, 6, 24, 48h for in vitro trial II. The inoculum were kept overnight in freezer or in refrigerator storage to test the effect of inoculum storage in the first experiment. The results were compared with fresh fecal inoculum sampled 2h prior to the in vitro trial. Gas production from both in vitro trial I and II showed that the replicates had a high similarity for all substrates, ß-glucan showed higher gas production than the other substrate types at the beginning of both fermentation trial I and II, while negative controls did not produce any gas. The pH were relatively stable over time in chambers with ß-glucan, while pH values for inulin and sucrose were reduced over time in both experiments I and II. All substrates resulted in higher SCFA levels after 24 and 48h. ß-glucan substrate induced an increase in SCFAs earlier than the other substrates tested. Propionate, and acetate, were dominant during the whole incubation time. In vitro trial II produced greater amount of SCFAs compared to in vitro trial I. The study did not demonstrate any difference in butyrate production between substrates tested. The results from second in vitro qPCR run showed the decreasing of proportion of Cq values in 10×dilution DNA samples which can justify an absolute increase in butyrate producing bacteria upon ß-glucan addition (r2= 0.9982). Results from this study also showed an increase in Cq value, i.e. reduction of butyrate producers at 48h of incubation. In addition, the overall performance of the PCR assay did not have a good efficiency. In conclusion the research did not demonstrate any difference in butyrate production between the substrates tested.
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