Total Short-chain Fatty Acid Production Research Articles

Chemical Composition, in Vitro Fermentation Characteristics, and in Vivo Digestibility Responses by Dogs to Select Corn Fibers

The objective was to examine the chemical composition, in vitro fermentation characteristics, and in vivo digestibility responses of fiber-rich corn coproducts resulting from corn wet milling. Native corn fibers, native corn fibers with fines, hydrolyzed corn fibers, and hydrolyzed extracted corn fibers were analyzed chemically and their capacity to produce short-chain fatty acids determined. Ash content was low (<1.2%), crude protein content varied little, but fat and fiber concentrations varied widely. Most fiber was in the insoluble form, with glucose being predominant followed by xylose. Total short-chain fatty acid production ranged from 211.6 to 699.52 micromol/g of dry matter, whereas branched-chain fatty acid production was low. Four corn fibers (native and processed) were included in a canine diet matrix at the 7% inclusion level. Nutrient digestibility, food intake, and fecal characteristics were not affected by corn fiber inclusion in canine diets, suggesting that they should be considered as potential dietary fiber sources in dog foods.

Digestion Residues of Typical and High-β-Glucan Oat Flours Provide Substrates for in Vitro Fermentation

In vitro fermentabilities of the oat flour digestion residues (ODR) from two commercial oat lines with 4.7 and 5.3% beta-glucan and from two high-beta-glucan experimental lines with 7.6 and 8.1% beta-glucan were evaluated and compared with fermentations of lactulose, purified oat beta-glucan (POBG), and purified oat starch (POS). Substrates were fermented by using an in vitro batch fermentation system under anaerobic conditions for 24 h. The progress of the fermentation was studied by following the change in pH of the fermentation medium, production of short-chain fatty acids (SCFA) and gases, and consumption of carbohydrates. The substrate from the flour with the greatest amount of beta-glucan tended to have the greatest pH decline and the greatest total SCFA production. A significant correlation occurred between gas production and SCFA formation (R 2 = 0.89-0.99). Acetate was produced in the greatest amounts by all of the substrates except POBG, by which butyrate was produced in the greatest amount. More propionate and butyrate, but less acetate, were produced from high-beta-glucan ODR. With the given fermentation conditions, >80% of the total carbohydrate was depleted by the bacteria after 24 h. Glucose was the most rapidly consumed carbohydrate among other available monosaccharides in the fermentation medium. Overall, the high-beta-glucan experimental lines provided the best conditions for optimal in vitro gut fermentations.

Biological short-chain fatty acids (SCFAs) production from waste-activated sludge affected by surfactant

Short-chain fatty acids (SCFAs), the preferred carbon sources for biological nutrient removal, are the important intermediate products in sludge anaerobic fermentation. Sodium dodecylbenzene sulfonate (SDBS) is a widespread used surfactant, which can be easily found in waste-activated sludge (WAS). In this investigation, the effect of SDBS on SCFAs production from WAS was investigated, and the potential of using fermentative SCFAs to promote enhanced biological phosphorus removal (EBPR) was tested. Results showed that the total SCFAs production increased significantly in the presence of SDBS at room temperature. At fermentation time of 6 days, the maximum SCFAs was 2599.1 mg chemical oxygen demand (COD)/L in the presence of SDBS 0.02 g/g, whereas it was only 339.1 mg (COD)/L in the absence of SDBS. The SCFAs produced in the case of SDBS 0.02 g/g and fermentation time 6 days consisted of acetic acid (27.1%), propionic acid (22.8%), iso-valeric acid (20.1%), iso-butyric acid (11.9%), n-butyric acid (10.4%) and n-valeric acid (7.7%). It was found that during sludge anaerobic fermentation, the solubilization of sludge particulate organic-carbon and hydrolysis of solubilized substrate as well as acidification of hydrolyzed products were all increased in the presence of SDBS, while the methane formation was decreased, the SCFAs production was therefore remarkably improved. Further investigation showed that the production of SCFAs enhanced by SDBS was caused mainly by biological effects, rather than by chemical effects and SDBS decomposition. With the fermentative SCFAs as the main carbon source, the EBPR maintained high phosphorus removal efficiency (∼97%).

The influence of addition of gallic acid, tannic acid, or quebracho tannins to alfalfa hay on in vitro rumen fermentation and microbial protein synthesis

Tannins may reduce rumen degradability of protein, increase the proportion of feed protein reaching the lower digestive tract for enzymatic digestion and thereby increase the efficiency of protein utilization. The objective was to assess the effects of different types and levels of tannins on rumen in vitro gas production and its kinetics, in vitro true degradability (IVTD) and rumen degradability of protein (IVRDP), and microbial protein synthesis by incubating alfalfa ( Medicago sativa L.) hay in buffered rumen fluid. Alfalfa was incubated in buffered rumen fluid with and without the addition of different levels of gallic acid (GA), quebracho tannin (QT), or tannic acid (TA). Tannins at the lower inclusion levels had minimal effects on fermentation products compared to the higher levels. Addition of QT and TA reduced ammonium-N (NH 4 +-N) concentration. Addition of QT at 20, 40, and 60 g/kg DM decreased NH 4 +-N by 2, 7, and 12% compared with control whereas addition of TA reduced NH 4 +-N by 5, 6, and 12% when added at 20, 40 and 60 g/kg DM, respectively. In experiment 2, addition of QT at 50, 100, and 150 g/kg DM, resulted in reduction of NH 4 +-N by 12, 30, and 51%, respectively, compared with the control. Addition of TA at 50, 100, and 150 g/kd DM reduced NH 4 +-N by 14, 26, and 47% compared with control. Inclusion of QT at 50, 100, 150 DM reduced IVRDP by 13, 30, and 36% compared with control whereas at these levels of inclusion, TA resulted in reduction of IVRDP by 14, 25, and 48%. Rate of gas production decreased (P<0.001), while asymptotic gas production increased (P<0.0001) with increasing level of GA and TA. Quebracho tannin decreased (P<0.0001) both the rate and asymptotic of gas production. Gallic acid had a positive effect on fermentation as indicated by increased gas production and total short chain fatty acids (SCFA) production. Quebracho tannin decreased 24 h gas production, IVTD, and total SCFA production. Acetate to propionate ratio increased with the addition of GA and but decreased when QT was added. Addition of tannins did not markedly increase total purines but numerical values tended to be higher in the presence of tannins compared with the control. Efficiency of microbial growth was lower in the presence of GA and unaltered by TA, but higher in the presence of QT compared with the control. The effect of tannins on rumen fermentation and protein degradation varied with type and level of tannins. In vivo studies will be conducted to validate the in vitro results.

In Vitro Fermentation by Human Fecal Microflora of Wheat Arabinoxylans

The fermentation of three arabinoxylan (AX) fractions from wheat by the human fecal microflora was investigated in vitro. Three AX fractions, with average molecular masses of 354, 278, and 66 kDa, were incorporated into miniature-scale batch cultures (with inulin as a positive prebiotic control) with feces from three healthy donors, aged 23-29. Microflora changes were monitored by the culture-independent technique, fluorescent in situ hybridization, and short chain fatty acid (SCFA) and lactic acid production were measured by high-performance liquid chromatography. Total cell numbers increased significantly in all treated cultures, and the fermentation of AX was associated with a proliferation of the bifidobacteria, lactobacilli, and eubacteria groups. Smaller but statistically significant increases in bacteroides and clostridia groups were also observed. All AX fractions had comparable bifidogenic impacts on the microflora at 5 and 12 h, but the 66 kDa AX was particularly selective for lactobacilli. Eubacteria increased significantly on all AX fractions, particularly on 66 kDa AX. As previously reported, inulin gave a selective increase in bifidobacteria. All supplemented cultures showed significant rises in total SCFA production, with a particularly high proportion of butyric acid being produced from AX fermentation. The prebiotic effect, that is, the selectivity of AX for bifidobacteria and lactobacilli groups, increased as the molecular mass of the AX decreased. This suggests that molecular mass may influence the fermentation of AX in the colon.

Minor effect of the dietary combination of probiotic Pediococcus acidilactici with fructooligosaccharides or polysaccharidases on beneficial changes in the cecum of rats

Abstract Effects of dietary fructooligosaccharides (FOS, 2% and 5%) and 2 polysaccharidases (glucanase and xylanase) with or without a probiotic preparation ( Pediococcus acidilactici ) on cecal fermentation of Wistar rats were studied. Cecal weight, pH of digesta, ammonia and protein concentrations, as well as bacterial enzymes activity and short-chain fatty acid (SCFA) production were assessed. Generally, the probiotic supplementation did not affect the cecal metabolism. Only SCFA profile showed a higher proportion of propionic acid in the probiotic-treated groups. A significant interaction was also found between probiotic and diet additives in the case of activities of β -glucuronidase ( P = .00005) and α -glucosidase ( P = .031). The cecal parameters of rats fed with the diet supplemented with polysaccharidases did not differ substantially from the control group; the only differences concerned a higher protein concentration as well as higher activities of β -glucosidase and β -galactosidase in the digesta. The cecum was affected, to the greatest extent, by FOS, regardless whether they were combined with probiotic or not. Rats treated with fructans (both levels) were characterized by the lowest pH value and ammonia concentration. Fructooligosaccharides applied at a higher dose enlarged the cecum (tissue and digesta) and decreased bacterial β -glucuronidase activity, compared with the control ( P = .05). The fermentation of the FOS-5% diet in the cecum was associated with the highest production of total and individual SCFAs. In conclusion, contrary to expectations, the effect of the polysaccharidases and the prebiotic FOS in the cecum of rats was not enhanced by the dietary treatments combined with the probiotic.

Cecal parameters of rats fed diets containing grapefruit polyphenols and inulin as single supplements or in a combination

Objective We compared the effects of grapefruit flavonoids and inulin, as single dietary components or in a combination, on cecal fermentation in rats adapted to a semipurified diet. Methods The experimental diets contained 0.3% flavonoid extract and 5% or 10% inulin and a combination of both supplements. The large bowel metabolism assessment was based on cecal parameters: bulk effect, pH, microbial enzymes activity, and short-chain fatty acid production. Results Both supplements induced significant enlargement of the cecal digesta weight. Acidification of cecal digesta was more pronounced, with a higher inulin addition to the diet. Cecal pH was the highest with the flavonoid-rich diets and lowest in the case of a simultaneous addition of flavonoids and a high content of inulin. The flavonoid extract applied as a single dietary supplement was observed to decrease the activity of bacterial β-glucosidase and β- and α-galactosidases in the cecal digesta. In contrast, addition of the grapefruit extract to inulin-containing diets increased the activity of α-glucosidase, α-galactosidase, and β-galactosidase. Great accumulation of cecal digesta in rats consuming the flavonoid-diet caused a considerable increase in the short-chain fatty acid pool, mainly acetic acid. Inulin added to the diet decreased the excessive enlargement of digesta caused by dietary flavonoids. Dietary addition of inulin to the flavonoid-diet also normalized hydration of cecal digesta and significantly decreased the pH of digesta. The presence of polyphenols in the inulin-containing diets did not change total short-chain fatty acid production in the cecum of rats. Conclusion Our results suggested that simultaneous intake of inulin and polyphenols can decrease the detrimental effects of the latter on cecal fermentation.

Improved Bioproduction of Short-Chain Fatty Acids (SCFAs) from Excess Sludge under Alkaline Conditions

The production of short-chain fatty acids (SCFAs) from excess sludge was conducted in batch fermentation tests at different pH values ranging from 4.0 to 11.0. Experimental results of the impacts of different pHs on SCFAs production showed that during the first 8-day fermentation time the total SCFAs production at either pH 9.0 or pH 10.0 was much greater than that at acidic or neutral pH, and the maximal yield of 256.2 mg SCFAs-COD per gram of volatile suspended solids (VSS) was at pH 10.0, which was, respectively, over3 and 4times that at pH 5.0 and uncontrolled pH. Clearly, SCFAs production from excess sludge could be significantly improved and maintained stable by controlling the fermentation pH at 10.0. The composition of SCFAs and the percent distribution of individual SCFAs accounting for total SCFAs at pH 10.0 were analyzed. The SCFAs consisted of acetic, propionic, iso-butyric, n-butyric, iso-valeric, and n-valeric acids, and acetic acid was the most prevalent product with a fraction of 40-55%. Because the results of this study were differentfrom those of previous studies of SCFAs production, the mechanism of increased SCFAs production under alkaline conditions was investigated. Results showed that as soluble COD increased, more soluble protein was provided as the substrate for producing SCFAs. In addition, less or even no SCFAs were consumed by methanogens at alkaline pH, so the SCFAs production was therefore remarkably improved. Further investigation revealed thatthe formation of SCFA at pH 10.0 was dominated by biological effects rather than by chemical hydrolysis.

Estimation of direct and indirect gas production in syringes: A tool to estimate short chain fatty acid production that requires minimal laboratory facilities

A technique is proposed that involves volumetric measurement of gas production in phosphate and bicarbonate buffered in vitro incubations in syringes. Gas production is measured before and after CO 2 absorption by injection of NaOH (10 M) at the end of the incubation. After correction for the amount of CO 3 2− in the rumen inoculum, measurements allow calculation of direct and indirect CO 2 production, reflecting metabolism and acidification, respectively, as well as methane (CH 4) production. This allows estimation of approximate short chain fatty acid (SCFA) production, energy lost as CH 4 and it might provide information on the ratio of the glucogenic to lipogenic SCFA produced. Results from in vitro gas production tests in syringes with straw (0.325 g), and eight different tropical seeds (0.125 g) as protein supplements, were used to evaluate whether such calculations could indeed predict measured amounts of SCFA and CH 4 produced, as determined by gas chromatography. The concordance correlation coefficient (CCC), representing both precision ( ρ) and accuracy ( C b) has been used to assess effectiveness of this reproducibility. It was found that indirect CO 2 production equimolarly reflects total SCFA production (CCC = 0.79; ρ = 0.86; C b = 0.93), whereas absorption of gaseous CO 2 provided an accurate prediction of CH 4 produced (CCC = 0.96; ρ = 0.96; C b = 1.00). The ratio of CH 4/gas indirect allowed estimation of the ratio of lipogenic to glucogenic SCFA produced ( R 2 = 0.73; R.S.D. = 0.20). However, the current approach did not allow accurate quantification of proportions of individual SCFA produced (CCC = 0.19; ρ = 0.83; C b = 0.23 for propionate proportions). The potential of a simple gas production technique to provide information on feed quality is illustrated, with the only apparatus required being gas tight syringes and incubation facilities.

Extrusion conditions affect chemical composition and in vitro digestion of select food ingredients.

An experiment was conducted to determine the effects of extrusion conditions on chemical composition and in vitro hydrolytic and fermentative digestion of barley grits, cornmeal, oat bran, soybean flour, soybean hulls, and wheat bran. Extrusion conditions altered crude protein, fiber, and starch concentrations of ingredients. Organic matter disappearance (OMD) increased for extruded versus unprocessed samples of barley grits, cornmeal, and soybean flour that had been hydrolytically digested. After 8 h of fermentative digestion, OMD decreased as extrusion conditions intensified for barley grits and cornmeal but increased for oat bran, soybean hulls, and wheat bran. Total short-chain fatty acid production decreased as extrusion conditions intensified for barley grits, soybean hulls, and soybean flour. These data suggest that the effects of extrusion conditions on ingredient composition and digestion are influenced by the unique chemical characteristics of individual substrates.

In vitro fermentation characteristics of selected oligosaccharides by swine fecal microflora1

The objective of this study was to quantify the fermentation characteristics of oligosaccharides present in feed ingredients or isolated for dietary supplementation. Substrates studied included short-chain fructooligosaccharides, medium-chain fructooligosaccharides, long-chain fructooligosaccharides, raffinose, stachyose, soy solubles, granular and liquid forms of transgalactooligosaccharides, glucooligosaccharides, mannanoligosaccharides, and xylooligosaccharides. Three healthy pigs that had never received antibiotics served as sources of fecal inoculum. Each substrate was fermented in vitro; samples were taken at 0, 2, 4, 8, and 12 h, and pH change and short-chain fatty acid (SCFA) and gas production determined. Gas production at 12 h did not differ (P > 0.05) among all fructooligosaccharides, transgalactooligosaccharides, soy solubles, and xylooligosaccharides. Raffinose, stachyose, and raffinose + stachyose fermentation resulted in the greatest (P < 0.05) gas production at 12 h of all substrates tested. The rate of gas production was greatest (P < 0.05) for stachyose and least (P < 0.05) for glucooligosaccharides and mannanoligosaccharides. Substrate did not affect (P > 0.05) time to attain maximal rate of gas production. The pH at 12 h for all fructooligosaccharides and xylooligosaccharides did not differ (P > 0.05). The pH values at 12 h for raffinose, stachyose, and raffinose + stachyose were highest (P < 0.05) compared with all other substrates. Total SCFA production at 12 h was similar for all fructooligosaccharides and transgalactooligosaccharides, glucooligosaccharides, and soy solubles. Total SCFA production was greatest (P < 0.05) for xylooligosaccharides, stachyose, and raffinose + stachyose, and least (P < 0.05) for mannanoligosaccharides and raffinose. Stachyose fermentation resulted in the greatest (P < 0.05) rate and earliest time to attain maximal rate of SCFA production. All oligosaccharides studied were readily fermentable but varied in amount and type of SCFA produced. Fermentation of the pure forms of oligosaccharides contained in soy solubles resulted in greater gas production and higher pH compared with soy solubles. The oligosaccharides in the soy solubles matrix seemed to behave differently than their pure counterparts. The high rates of fermentation of most oligosaccharides tested indicate that they may serve as fermentable carbohydrate sources in the terminal small intestine or large intestine of swine.

Fecal Inoculum Can Be Used to Determine the Rate and Extent of In Vitro Fermentation of Dietary Fiber Sources across Three Lemur Species That Differ in Dietary Profile: Varecia variegata, Eulemur fulvus and Hapalemur griseus

To estimate fermentative capacity among lemur species, four fiber substrates were tested across three species, Eulemur fulvus, Hapalemur griseus and Varecia variegata. The substrates, cellulose, beet pulp, citrus pulp and citrus pectin, ranged in composition from completely insoluble fiber (IF) to completely soluble fiber (SF), respectively. The lemurs consumed a nutritionally complete biscuit formulated for primates [85 g/100 g diet dry matter (DM)] and locally available produce (15 g/100 g diet DM). Feces were then collected and used to inoculate fermentation tubes prefilled with fiber substrates and an anaerobic growth medium. Dry matter disappearance (DMD), and acetate, propionate, butyrate, and total short-chain fatty acid (SCFA) production were measured in tubes subjected to 6, 12, 24 or 48 h of fermentation. Results were fitted to a logistic growth model. The maximal production (MP) time at which production or disappearance is at one-half maximum (t(50)) and the fermentation rate at 3 h were calculated. The maximal disappearance of DM differed among substrates (citrus pectin > citrus pulp > beet pulp; P < 0.0001) and species (E. fulvus > H. griseus > V. variegata; P < 0.001). V. variegata reached t(50) for acetate and total SCFA production faster than H. griseus or E. fulvus (P < 0.02). Three-hour production rates of acetate and total SCFA were also greater for V. variegata for citrus pulp and citrus pectin (P < 0.01). Few species differences were observed for beet pulp. Results provide evidence for differences in fermentative capacity and suggest that fiber solubility and fermentability should be considered when assessing the nutritional management of lemurs.

In Vitro Fermentation Properties of Selected Fructooligosaccharide-Containing Vegetables and In Vivo Colonic Microbial Populations Are Affected by the Diets of Healthy Human Infants

Salsify (Tragopogon porrifolius) and gobo (Arctium lappa) are root vegetables that contain high concentrations of naturally occurring fructooligosaccharides (FOS), nondigestible oligosaccharides that have prebiotic effects on the intestinal microflora. The objective of this study was to compare colonic microbial populations and the fermentation characteristics of gobo and salsify in breast-fed vs. formula-fed infants. Fecal inoculum from breast-fed and formula-fed infants consuming either no solid foods, cereal, or fruit and vegetable purees were fermented in vitro with sweet potato puree plus gobo, salsify puree or a control vegetable, carrot. Breast-fed and formula-fed infants had similar fecal bacteria concentrations, with the exception of Clostridium perfringens (P < 0.10). Introduction of solid foods into the diet of infants was associated with increased fecal concentrations of bifidobacteria (P < 0.10) and decreased concentrations of total aerobes (P < 0.01), C. perfringens (P < 0.001) and Escherichia coli (P < 0.10). Inoculum from feces of breast-fed infants resulted in greater acetate production, whereas inoculum from feces of formula-fed infants resulted in greater propionate and butyrate production (P < 0.05). Fermentation of FOS-containing vegetables by infant fecal inoculum did not differ significantly from fermentation of carrots as assessed by total short-chain fatty acid (SCFA) production. The addition of solids to the diet of infants was associated with increased production of acetate and total SCFA (P < 0.05). It appears that both the composition and fermentative activity of the colonic microflora of human infants is affected by breast-feeding and solid food consumption, but not by short-term exposure to low concentrations of FOS-containing substrates.

Colonic fermentation as affected by antibiotics and acidic pH: Application of an in vitro model.

Antimicrobial substances such as vancomycin or metronidazole suppress normal gut flora, thereby preventing physiological fermentation of colonic substrates that may promote mucosal inflammation. This study was designed to establish an in vitro model of microbial metabolism in the colon under control and disturbed conditions (acidic pH) to investigate specific effects of vancomycin and metronidazole on the production of short chain fatty acids (SCFA), which play a pivotal role in maintaining homeostasis in the colon. The experiments were carried out with the colon simulation technique (Cositec) representing an in vitro model for the semi-continuous incubation of defined colon contents. Inocula and fermentable substrates were sampled from cecal contents of fistulated pigs. Disturbed microbial metabolism was generated by reduction of pH in the fermentation vessels from 6.7 to 5.8 and 5.1. In general, application of either vancomycin or metronidazole resulted in a significant decrease of SCFA production rates indicating substantial disturbance of the homeostasis of microbial metabolism. With low doses of vancomycin acetate and butyrate production rates were reduced and with high doses of the antibiotic propionate production was inhibited to a greater extent. Treatment with metronidazole inhibited butyrate production almost completely. Similarly, low pH caused a reduction in total SCFA production, which was mainly due to respective decrease of acetate synthesis. Metronidazole effects were not consistently changed at low pH. The Cositec system provides an excellent facility to test the effects of different antibiotics under defined conditions. In this study, both vancomycin and metronidazole affected microbial metabolism to a considerable extent. Both substances may thus be responsible for disturbances of colon function in vivo.

Glucose-Based Oligosaccharides Exhibit Different In Vitro Fermentation Patterns and Affect In Vivo Apparent Nutrient Digestibility and Microbial Populations in Dogs

To evaluate the potential of indigestible oligosaccharides (OS) to serve as "dietary fiber-like" ingredients, it is necessary to determine their extent of indigestibility. In vitro fermentation characteristics of two novel OS, alpha-glucooligosaccharides (GOS) and a maltodextrin-like OS (MD), were compared to those of fructooligosaccharides (FOS), gum arabic (GA), guar gum (GG) and guar hydrolysate (GH). Total short-chain fatty acid (SCFA) production (micromol/g dry matter) as a result of MD fermentation was higher initially compared with GA (P<0.01), but GA was more extensively fermented at 24 h (P<0.01). Total SCFA production for GOS was similar to that for FOS, GG, GH and GA. In the second experiment, GOS and MD were added at 6% to an enteral formula control diet (Control) and fed to ileal-cannulated dogs in a 3x3 replicated Latin-square design. Ileal digestibility of glucose was lower (P<0.05) and carbohydrate (CHO) numerically lower (P = 0.08) for both GOS and MD compared with the Control. Total tract digestibility of CHO and glucose was lower only for MD (P<0.01) compared with the Control. Total fecal weights were higher (P<0.01) for both GOS and MD treatments. Fecal concentration of bifidobacteria was numerically increased by GOS and MD supplementation (P = 0.13 and 0.23, respectively). Thus, GOS and MD are indigestible yet fermentable OS, and may act as "dietary fiber-like" ingredients.

In vitro fermentation of different types of dietary fiber in ulcerative colitis: Production of butyrate

In a previous study we observed that a dietary fiber which yields butyrate in the colon (Plantago ovata seeds) was able to maintain remission in ulcerative colitis (UC) as compared to mesalazine (Am J Gastroenterol 1999). Recently, different studies have shown that butyrate may have an anti-inflammatory effect by modulating the release of pro-inflammatory cytokines. Aim: To assess in vitro the ability of different types of dietary fiber to yield short chain fatty acids (SCFA), especially butyrate, in patients with UC in remission. Methods: Fresh stools specimens were collected from 8 patients with UC in remission. Fecal homogenates (feces diluted 1:5 with sodium bicarbonate) were incubated under anaerobic conditions (nitrogen), at 37°C for 0, 6 and 24 h, with the different types of fiber as dry power (20 mg/ml): Fiber A, Plantago ovata seeds; Fiber B, Plantago ovata husk (POH); Fiber C, POH+ Resistant starch 1 g; Fiber D, POH+Resistant starch 0.5 g. Fecal suspensions without additions served as control. The bacterial fermentation was stopped by freezing at -80°C. SCFAs were determined by GLC using a semicapilar column. Friedman s two-way analysis of variance for repeated measures was used in the statistical analysis. Results: A significant increase in total SCFA production at 6 hand 24 h was observed with all fibers as compared to basal values. Results at 6 h and 24 h are shown in the Table (a% respect to basal value; p<0.005 vs No fiber at 24 h). Butyrate levels were higher with Fiber A than with the other types of fiber (24 h: 19.6±3 vs 13.6±3, l6.2±3, l4.1±3 mmol/g, p=0.07 vs others and p=0.04 vs Fiber B; 8.3±O.8 vs 5.2±0.7, 6.5±O.9, 5.4±0.6 percent of Total SCFAs, p=O.OO6 vs others). Conclusions: Although all types of fiber studied produce in vitro similar amounts of SCFA, Plantago ovata seeds showed a higher trend to produce butyrate. 4763

Production of Short-Chain Fatty Acids (SCFA) During in vitro Fermentation of Fibers

Increasing dietary fiber has been shown to improve colonic health and reduce the risk of colon cancer. One aspect of fiber consumption is its fermentation by colonic microflora to produce short-chain fatty acids (SCFA). The major SFCA produced are acetic, propionic and butyric acids. Butyric acid is absorbed by the colonic mucosa as its major energy source. The concentration of SCFA in the feces can be measured and the results extrapolated to production in the colon. However, this is probably not a true reflection of SCFA production since SCFA are absorbed and utilized by the colon epithelial cells. In our study, fresh fecal samples were mixed with 9 different fibers with glucose serving as the control, incubated at 37°C for 24h. SCFA production was measured at 0,4,8,12, and 24h. This approach avoids loss of SCFA by absorption into the body. SCFA production after 24h was 42.35 ± 5.5mg/ml for 8 of the 10 samples. Unifiber™ had a lower production of total SCFA (33.5mg/ml) after 24h and Benefiber™ had a high production of SCFA (54.6mg/ml). To allow for differences in total SCFA production, the percentage of total SCFA was calculated for three major fatty acids. Percent averages after 24h were: Acetic acid 44.9% ± 12.9. with the highest production from glucose and the lowest from cellulose, 69.2% and 17.7%, respectively. Propionic acid 32.5% ± 10.4, with the highest from cellulose and the lowest from glucose, 55% and 20.2%, respectively. Butyric acid 22.3% ± 9.0, with the highest from Metamucil™ and the lowest from cellulose, 38.5% and 9.0%, respectively. There was no consistent pattern as to when the SCFA are formed over the 24h period. Thus, in vitro fermentation of different fibers ail yield SCFA, but the concentrations of the various SCFAs vary among the fibers.

Effects of Guar Gum and Cellulose on Cecal Enzyme Activity and Cecal Short-Chain Fatty Acids in Young and Aged Mice

The effects of cellulose or guar gum on cecal enzyme activity and cecal short-chain fatty acids (SCFAs) in young and aged mice were studied. Male Crj:CD-1 (ICR) mice were fed an MF diet for 4 (young mice) or 23 months (aged mice). The MF diet was then replaced with a semisynthetic diet supplemented with 5% guar gum or 5% cellulose. The mice were fed the guar gum or cellulose diet for 3 weeks. There was no significant difference in cecal content between the two diet groups. There were no significant differences in total short-chain fatty acid production between the young mice fed the cellulose and those fed the guar gum diet, and between the aged mice fed the cellulose and guar gum diet. There were significant differences in cecal enzyme activity between the young mice fed the cellulose and those fed the guar gum diet. β-Glucuronidase activity was significantly higher in the young mice fed the guar gum diet than in those fed the cellulose diet. There were also significant differences in cecal enzyme activity between the aged mice fed the cellulose diet and those fed the guar gum diet. β-Glucuronidase activity was significantly higher in the aged mice fed the guar gum diet than in these fed the cellulose diet. β-Glucosidase activity was significantly lower in the aged mice fed the guar gum diet than in those fed the cellulose diet. The effect of cellulose on the microflora between the young and aged mice might be different from the effect of guar gum. The degree of adaptation to the diet of microflora in young and aged mice fed the cellulose diet might differ from that in those fed the guar gum diet. The higher enzyme activities of microflora in aged animals compared to young animals, might have some relation with the incidence of colon cancer in aged animals.

In vitro fermentation and hydration properties of commercial dietary fiber-rich supplements

Eight commercial dietary fiber (DF)-rich supplements were analyzed in vitro to assess swelling, water retention capacity (WRC) and fermentation. The supplements were fermented with rat cecal as inoculum for 24 h, and short chain fatty acid (SCFA) production, fermentability, dry matter disappearance (DMD) and gas production were determined. Products containing mainly soluble fiber components (Metamucil, Humamil, Fybogel and Fibraplan) showed the highest capacity of retaining water and fermentability. Swelling (mL per g dry matter) ranged from 6.2 for Fibra Leo Apple Prune to 24 for Fibraplan. Total SCFA production was significantly correlated to DMD (r = 0.969, R 2 = 0.9385) and to gas production (r = 0.901, R 2 = 0.8113). Hydration properties and fermentative characteristics were different among the studied supplements, these in vitro techniques could be useful to evaluate their potential physiological effects.

In Vitro Fermentation of Various Food Fiber Fractions

Dietary fiber fractions (DFF) were fermented in vitro with human fecal inocula to study fiber fermentability and production of short-chain fatty acids (SCFA). Amylolytic and proteolytic enzyme treatment using the Association of Official Analytical Chemists enzymatic-gravimetric procedure reduced processed food fiber products to DFF by removing gastric enzyme-digestible (nonresistant) components. Total 24-h SCFA production from DFF decreased in the following order: fig > oat = soy > pea > apple > corn = wheat > pear. SCFA production was proportional to the fermentability of these fibers. Fermentation of DFF from fruits such as pear, apple, and fig produced low amounts of butyrate. In contrast, less acetate and more propionate and butyrate were produced by fermentation of oat and soy DFF. Major fiber constituents, resistant starch (RS), β-glucan, and pectin were also fermented. RS, isolated from starch, produced acetate more slowly than the starch. β-Glucan produced propionate and butyrate in higher amount...