Effects of maternal undernutrition during late gestation and/or lactation on colostrum synthesis and immunological parameters in the offspring.

The emerging immune system is vulnerable to insult not only during fetal life, but also through colostrum transfer of maternal factors with immunomodulatory functions. The aim of the present study was to examine the effects of maternal undernutrition during late gestation and/or lactation on colostrum and milk synthesis, as well as on immunological parameters in offspring. Pregnant ewes were fed to 100% of nutrient requirements throughout pregnancy and lactation (Control) or to 50% during lactation (R1) or during the last 20 days of pregnancy and lactation (R2). Colostrum samples were collected 3 and 18h after parturition and thymus glands were obtained from 5-month-old offspring. Lamb birthweight did not differ between groups, whereas growth rate was significantly lower in males in the R1 group and in females in both undernourished groups. There was a significant reduction in lactose percentage in the 18-h colostrum of the R2 group. The IgG concentration, as a percentage of protein, was significantly increased in 3-h colostrum samples of the R2 group. Quantitative polymerase chain reaction analysis revealed a significant increase in the expression of Toll-like receptor (TLR) 2, TLR4 and TLR9 in the thymus gland of female lambs in both undernourished groups. In conclusion, early life nutritional imbalances may impact on immune system function in later life due to programming effects.

Evaluation of yeast dietary supplementation in broilers challenged or not with Salmonella on growth performance, cecal microbiota composition and Salmonella in ceca, cloacae and carcass skin.

The dietary supplementation of Saccharomyces cerevisiae var. boulardii was evaluated in broilers challenged or not challenged with Salmonella Enteritidis (SE) using a 2 × 2 factorial arrangement. Depending on yeast inclusion at 0 (C) or 1 × 109 cfu/kg diet (Y) and SE challenge (0 or log 6.3 cfu/bird) on d 15, the experiment had four treatments C, Y, C-SE, and Y-SE, respectively. Each treatment had seven replicate floor pens with 15 broilers. Growth performance responses were determined weekly and overall for the 5 week experimental period. Salmonella levels and prevalence in ceca, cloacae, and carcass skin were determined by culture procedures, while cecal microbiota was determined by real time PCR. Yeast supplementation had no effect (PY > 0.05) on growth performance. For the overall post SE-challenge period (i.e., wk 3 to wk 5), Salmonella reduced body weight gain (BWG) (PSE < 0.001), feed intake (FI) (PSE = 0.032), and the European production efficiency (EPEF) factor (PSE = 0.005). Broilers Y-SE had higher (P < 0.001) overall BW gain compared to C-SE ones. Overall mortality was 2.14% and did not differ (P > 0.05) between treatments. Reduced Salmonella levels in the cloacae (P = 0.014) and on the breast skin (P = 0.006) and lower prevalence on the neck skin (P = 0.007) were noted for treatment Y-SE compared to C-SE. Yeast supplementation did not have an effect (P > 0.05) on cecal microbiota composition at d 1 and d 21 post SE-challenge. On the contrary, SE-challenge reduced cecal levels of total bacteria (PSE = 0.002), E. coli (PSE = 0.006), Bifidobacterium spp. (PSE = 0.006), Bacteroides spp. (PSE = 0.010), and Clostridial populations belonging to cluster I and cluster XIVa, (PSE = 0.047 and PSE = 0.001, respectively) on d 1 post SE-challenge. At 21 d post SE-challenge, only the levels of cecal Lactobacillus spp. (PSE = 0.001) and Bifidobacterium spp. (PSE = 0.049) were reduced compared to the non SE-challenged groups. In conclusion, yeast supplementation in SE challenged broilers (Y-SE) was beneficial for growth performance and reduced Salmonella presence compared to C-SE ones. The disturbance of cecal microbiota balance by SE merits further investigation for potential implications in gut and overall bird health.

Dietary probiotic inclusion level modulates intestinal mucin composition and mucosal morphology in broilers.

The aim of this study was to investigate the effect of dietary probiotic inclusion level on mucin composition (monosaccharide ratio), mucosal morphometry, mucus layer staining intensity, and mucus layer thickness along the broiler intestinal tract. One-day-old male Cobb broilers were administered maize-soybean meal basal (BD) diets for 42 d and depending on the feed additive used, broilers were allocated into the following 5 experimental treatments: control C (BD, no additive), treatment P1 (10(8) colony forming units of probiotic/kg of BD), treatment P2 (10(9) cfu of probiotic/kg of BD), treatment P3 (10(10) cfu of probiotic/kg of BD), and treatment A (2.5 mg avilamycin/kg of BD). Intestinal samples from duodenum, ileum, and cecum of 14- and 42-d-old broilers were collected and analyzed. Mannose (Man) decreased linearly with increasing probiotic level in duodenum (P=0.015) and ileum (P=0.042) of 14-d-old broilers. N-Acetyl-glucosamine and galactose decreased linearly (P=0.012 and P=0.001, respectively), while fucose increased linearly (P<0.001) with increasing probiotic feed inclusion level in 42-d-old broiler cecum, with treatment A not differing from treatment C (P≥0.05). Cecal villus height and crypt depth increased linearly (P=0.016 and P=0.003, respectively) with probiotic inclusion level, with treatment A having higher (P≤0.05) values only from treatment C. Mucus layer thickness increased linearly with probiotic inclusion level in duodenum at 14 d and 42 d (P=0.007 and P=0.030, respectively). Finally, mucus layer staining intensity was influenced (P<0.001) by villus fragment (i.e., tip, midsection, and base) but not from the treatment, age, and intestinal segment examined. As a conclusion, this study provides evidence that probiotic inclusion level affects intestinal mucin monosaccharide composition, mucus layer thickness, and intestinal morphology in broilers.

Effect of banana consumption on faecal microbiota: a randomised, controlled trial.

Banana is a widely consumed fruit, which contains considerable amounts of potential prebiotic indigestible carbohydrates. In our randomised, controlled trial we aimed to evaluate the in vivo prebiotic effect of banana consumption on faecal microbiota. Thirty-four healthy women participated in the study, having Body Mass Index (BMI) 24-30 kg/m(2), age 19-45 years, without history of gastrointestinal disease and no antibiotic and other medication use two months prior the initiation and during the study. All women were asked to maintain their usual dietary habits for 60 days and they were randomly assigned to consume twice a day a pre-meal snack, either one medium banana, or one cup of banana-flavoured drink or one cup of water (control group). Stool samples were collected at baseline, on days 30 and 60 of intervention for enumeration of total anaerobes, bifidobacteria and lactobacilli by plate count techniques, as well as for pH and short chain fatty acids (SCFAs) measurement. Gastrointestinal symptoms were also recorded. Mean bifidobacterial levels were increased only in the banana group both at 30 and 60 days of intervention, but this change did not reach a statistical significance. No significant overall differences in the total concentrations and molar ratios of SCFAs were detected according to dietary intervention. Analysis of the gastrointestinal symptoms records revealed significantly lower bloating levels in the banana group, compared to controls, at 26-35 days (p = 0.009) and 51-60 days (p = 0.010). Banana consumption had also no adverse effects on evacuation patterns. We concluded that daily consumption of bananas is a well-tolerated eating behaviour, which may induce bifidogenesis in healthy women experiencing body weight problems.

Impact of beta-glucan on the faecal microbiota of polypectomized patients: a pilot study.

Beta-glucans are polysaccharides present in the cell walls of higher plants, in the seeds of some cereals, and certain yeasts and fungi also produce them. It is suggested that they exhibit, among many other health benefits, protective effects against carcinogenesis in the colon, but there is not enough human data to support this. The aim of the study was to determine the effect of barley-derived beta-glucan in the gut microbiota of polypectomized patients. Subjects were randomly assigned to consume 125 g of bread per day with beta-glucan (3 g/d), or without (placebo group), for 3 months. Thirty-three polypectomized men and women (mean age 57.6 years) were recruited into the study, but only 20 completed. Subjects did not consume any probiotics, prebiotics or antibiotics 2 months prior the intervention, or during the study. Stool samples were collected at baseline, on days 30 and 90 of intervention, as well as 2 weeks after the intervention, for enumeration of total aerobes and anaerobes, coliforms, E. coli, enterococci, Bacteroides spp., Clostridium perfringens, bifidobacteria, lactobacilli and Candida spp. Faecal bacterial enzyme activity (beta-glucuronidase and beta-glucosidase), pH, faecal moisture and the concentration of volatile fatty acids in the faeces were measured. Gastrointestinal symptoms were also recorded. Overall, no significant differences were observed in bacterial viable counts between the two feeding groups. Group specific analysis for ß-glucan group revealed significantly decreased total coliform counts on the 30th day of the trial compared to the baseline (p = 0.041). Clostridium perfringens concentration increased without reaching statistical significance, on the 30th day, while it decreased significantly on the 90th day of the intervention compared to the 30th day (p = 0.016). An increase was noted in the molar ratio of acetate on the 90th day of the trial compared to placebo (p = 0.018). The molar ratio of butyrate presented a trend to increase on the 30th day, which decreased (p = 0.013) on the 90th day and then increase 2 weeks after the intervention (p = 0.017) compared to placebo. A decrease was recorded in the ß-glucan group in the bloating and abdominal pain score after the 30th day of the intervention (Day 30-37) compared to placebo. During ß-glucan administration we did not observe any changes on beta-glucuronidase or beta-glucosidase activity, faecal pH, or on faecal moisture.

Caecum odd-numbered and branched-chain fatty acid composition in response to dietary changes in fattening rabbits.

The study aimed to describe the interactions between nutrition and caecal bacteria abundance using odd-numbered and branched-chain fatty acids (OBCFA). Following a 2 × 2 factorial design, 47 rabbits were fed diets with two levels of digestible fibre (DF, 180 vs. 260 g/kg DM) supplemented with soybean oil (SO, 20 g/kg) or not. At 77 days of age, fatty acid (FA) composition was determined in caecal contents. The microbial origin of OBCFA vs. dietary FA in caecal contents was illustrated by clustering of these FA in the loading plots of principal component analysis. The contribution of odd-numbered FA in the OBCFA pattern was increased (p < 0.05) for high DF diets, whereas that of branched-chain FA decreased (p < 0.05), indicating potential shifts in the relative abundance of Gram-negative and Gram-positive fibrolytic bacteria respectively. Soybean oil reduced the relative importance of OBCFA (p < 0.001) in total microbial FA; however, its effects appeared to depend on the readily available fermentable substrate, as indicated by the DF × SO interactions (p < 0.001). In conclusion, OBCFA may be potentially used as markers of caecum function, but further detailed studies are necessary to validate their use as diagnostic tools in rabbit nutrition.

Effects of probiotic inclusion levels in broiler nutrition on growth performance, nutrient digestibility, plasma immunoglobulins, and cecal microflora composition.

The aim of this work was to investigate the effect of inclusion levels of a 5-bacterial species probiotic in broiler nutrition. Five hundred twenty-five 1-d-old male Cobb broilers were allocated in 5 experimental treatments for 6 wk. The experimental treatments received a corn-soybean coccidiostat-free basal diet and depending on the addition were labeled as follows: no addition (C), 10(8) cfu probiotic/kg of diet (P1), 10(9) cfu probiotic/kg of diet (P2), 10(10) cfu probiotic/kg of diet (P3), and 2.5 mg of avilamycin/kg of diet (A). Each treatment had 3 replicates of 35 broilers each. Treatment effects on broiler growth performance and biomarkers such as ileal and total tract nutrient digestibility, plasma Ig concentration, and cecal microflora composition were determined. Differences among treatments were considered significant when P < or = 0.05. Overall BW gain was significantly higher in treatment P1 (2,293 g) compared with P2 (2,163 g), C (2,165 g), and P3 (2,167 g), with A (2,230 g) being intermediate and not different from P1. Overall feed conversion ratio values were similar and significantly better for P1 (1.80) and A (1.80) compared with P2 (1.87), C (1.89), and P3 (1.92). Ileal apparent digestibility coefficients (ADC) of CP and ether extract were higher in A. Generally, treatments A and P1 showed an improved total tract ADC for DM, organic matter, ash, ether extract, and AME(n) values. The total tract ADC of CP was higher in P1, C, and P2. There were no differences between treatments regarding plasma Ig in 14- and 42-d-old broilers. Treatments P2 and P3 were effective at beneficially modulating cecal microflora composition. In particular, the lower cecal coliform concentration (log cfu/g of wet digesta) was seen in P2 (6.12) and P3 (4.90) in 14- and 42-d-old broilers, respectively, whereas at 42 d, P3 and P2 had the highest Bifidobacterium (8.31; 8.08) and Lactobacillus concentrations (8.20; 7.86), respectively. It is concluded that probiotic inclusion level had a significant effect on broiler growth responses, nutrient ADC, AME(n), and cecal microflora composition.

Effects of a multi-species probiotic on biomarkers of competitive exclusion efficacy in broilers challenged with Salmonella enteritidis.

1. Probiotics are beneficial microbes that are currently considered as alternatives to antimicrobial growth promoters (AGP) in animal nutrition. In addition, they are purported to suppress pathogens in the gut via the concept of competitive exclusion (CE). The aim of this work was to evaluate the efficacy of a multistrain probiotic against Salmonella enteritidis (SE) in broilers. 2. Three hundred and four, one-day-old, male Cobb broilers were fed a corn-soybean basal diet and were allocated to four experimental treatments for 6 weeks. Three of the four treatments were challenged with SE. Treatments were: C- (Negative Control, no SE challenge), C+ (Positive control, SE challenge, no other additives), AB (SE challenge + Avilamycin used as AGP) and PFW (SE challenge + probiotic in feed and water). Morbidity, mortality, incidence of Salmonella positive broilers, cecal microflora composition and antibody response (IgA and IgG) in the blood and intestine were determined as biomarkers of probiotic CE efficacy against SE. 3. The three SE challenged treatments had a significantly higher morbidity compared to C- during the first 2 weeks of age, while there were no differences between treatments regarding mortality. Salmonella shedding was evidenced in 75 and 50% of the birds at 5 and 21 d post-challenge, respectively. Microbiological analysis of cecal digesta in 42-d-old broilers revealed that while broilers in treatment C+ were 100% Salmonella positive, the broilers in treatments PFW and AB were 50% positive and in addition they had lower Salmonella levels (CFU/g digesta) by 27 logs compared to C+. At the age of 42 d significantly higher IgA and IgG specific immune responses against SE were detected at systemic and at intestinal level only for the positive control treatment (C+). 4. In conclusion, the lack of significant levels of specific IgA and IgG against SE at systemic and intestinal level combined with the lower prevalence of SE positive broilers and the lower cecal SE levels in treatments AB and PFW compared to C+, suggest that treatments PFW and AB were efficacious at reducing SE.

Evaluation of the efficacy of a probiotic containing Lactobacillus, Bifidobacterium, Enterococcus, and Pediococcus strains in promoting broiler performance and modulating cecal microflora composition and metabolic activities.

The aim of this work was to investigate the efficacy of a new multibacterial species probiotic in broiler nutrition. The probiotic contained 2 Lactobacillus strains, 1 Bifidobacterium strain, 1 Enterococcus strain, and 1 Pediococcus strain. Four hundred 1-d-old male Cobb broilers were allocated in 4 experimental treatments for 6 wk. The experimental treatments received a corn-soybean basal diet and were as follows: "control," with no other additions; "probiotic in feed and water," (PFW) with probiotic administered at 1 g/kg of feed for the whole period and in water on scheduled intervals during the first 4 wk; "probiotic in feed," (PF) with probiotic in feed as in PFW; and "antibiotic," (AB) with addition of avilamycin at 2.5 mg/kg of feed. Salinomycin Na was used as a coccidiostat. Each treatment had 5 replicates of 20 broilers. Treatment effects on parameters of broiler performance and cecal microbial ecology were determined. Broiler BW, feed intake, and feed conversion ratio were determined on a weekly and overall basis. Cecal microflora composition, concentration of volatile fatty acids, and activities of 5 bacterial glycolytic enzymes (alpha-galactosidase, beta-galactosidase, alpha-glucosidase, beta-glucosidase, and beta-glucuronidase) were determined at the end of the experiment. Overall, treatment PFW displayed a growth-promoting effect that did not differ from AB. Overall, feed conversion ratio in treatment AB was significantly better (P < or = 0.01) than the control treatment, whereas treatments PFW and PF were intermediate and not different from AB. Concentrations of bacteria belonging to Bifidobacterium spp., Lactobacillus spp., and gram-positive cocci were significantly (P < or = 0.05) higher in treatments PFW and PF compared with the control and AB treatments. Treatments PFW and PF had significantly higher specific activities of alpha-galactosidase and beta-galactosidase compared with the control and AB treatments. In conclusion, probiotic treatment PFW displayed a growth-promoting effect that was comparable to avilamycin treatment. In addition, treatments PFW and PF modulated the composition and, to an extent, the activities of the cecal microflora, resulting in a significant probiotic effect.

Effects of increasing dietary organic selenium levels on meat fatty acid composition and oxidative stability in growing rabbits.

The effects of dietary organic selenium (Se) addition at 0.1, 0.5 and 2.5mg/kg vs. an unsupplemented basal diet (BD) on performance, fatty acid (FA) composition and oxidative stability were studied in muscle tissue of growing rabbits. Muscle Se content increased (P<0.001) in a dose dependent manner with dietary Se inclusion. Saturated FA (SFA) were affected linearly (P<0.05) and quadratically (P<0.05) by dietary Se addition. Polyunsaturated FA (PUFA) increased linearly (P<0.01) resulting in a linear increase in the PUFA:SFA ratio (P<0.01) with dietary Se increment. Feeding 0.5mgSe/kg diet reduced malondialdehyde (MDA) and oxygen radical absorbance capacity (ORAC) values in the muscle, whilst 2.5mgSe/kg diet increased MDA concentrations and tended to increase ORAC values, likely indicating oxidative stress. In conclusion, dietary Se supplementation at 0.5mg/kg improves meat FA composition and oxidative stability, whereas at 2.5mg/kg may induce pro-oxidant effects.

Probiotic form effects on growth performance, digestive function, and immune related biomarkers in broilers.

The aim of this work was to assess the effect of dietary viable or heat inactivated probiotic forms (PF) combined or not with avilamycin (AV) used as a growth promoter, on broiler growth performance, nutrient digestibility, digestive enzyme activities, and expression of immune response related genes.Depending on the type of PF (i.e., no addition, viable, inactivated) and AV addition (no/yes), 450 one-day-old Cobb male broilers were allocated in the following 6 treatments according to a 3 × 2 factorial arrangement with 5 replicates of 15 broilers each for 6 wk: CoN: diet without any addition; CoN+A: combination of CoN with AV; ViP: viable PF - no AV; ViP+A: combination of ViP with AV; InP: inactivated PF - no AV; InP+A: combination of InP with AV.There were no interactions (P > 0.05) for overall performance parameters. In contrast, PF or AV addition improved BW gain (PPF= 0.015; PAV < 0.001), FCR (PPF < 0.001; PAV < 0.001) and production efficiency factor (PPF= 0.001; PAV= 0.001).Significant (PPF×AV ≤ 0.05) interaction effects regarding ileal digestibility (IAD) of DM and total tract apparent digestibility (TTAD) of DM and ether extracts (EE) were noted. In addition, PF affected IAD and TTAD of CP (PPF < 0.001, PPF= 0.004, respectively). Inactivated PF increased (PPR= 0.024) lipase activity in jejunal digesta.At spleen level InP and ViP+A down-regulated TGF-ß4 (PPF × AV = 0.035) compared to CoN and ViP, whereas ViP+A up-regulated iNOS (PPF × AV = 0.022). An anti-inflammatory effect of live and inactive PF and/or AV addition at cecal tonsils was shown by iNOS down-regulation (PPF × AV= 0.015) compared to CoN. Furthermore, AV down-regulated IFN-γ (PAV= 0.002).In conclusion, viable probiotic, as well as inactivated probiotic alone or in combination with avilamycin, improved nutrient digestibility. All dietary additives affected growth performance positively and induced an anti-inflammatory response at cecal level.

Effect of cinnamon (Cinnamomum zeylanicum) essential oil supplementation on lamb growth performance and meat quality characteristics.

A trial was conducted to examine the effect of cinnamon essential oil supplementation on lamb growth performance and meat quality. Sixteen male lambs were randomly assigned to two groups. The first group served as control and was given a basal diet, and the second group was given the same diet supplemented with cinnamon oil (1 ml/kg of concentrated feed) for 35 days. Incorporation of cinnamon oil did not affect growth performance (P>0.05). Meat pH, colour, water-holding capacity, shear force, intramuscular fat and lipid oxidation values of longissimus thoracis muscle were not significantly influenced by cinnamon oil supplementation (P>0.05). The post-inoculation counts of Salmonella enteritidis and Listeria monocytogenes on raw meat during refrigerated storage for 6 days did not differ (P>0.05) between the two groups. The results show that cinnamon oil supplementation may not have the potential to improve lamb growth performance and meat quality characteristics.

Modulation of intestinal mucin composition and mucosal morphology by dietary phytogenic inclusion level in broilers.

The effect of a dietary phytogenic feed additive (PFA) inclusion level in mucin monosaccharide composition, mucosal morphometry and mucus histochemistry along the broiler intestinal tract was studied. Cobb male broilers (n = 525) were allocated into five experimental treatments that, depending on the type of addition in the basal diet (BD), were labeled as follows: C (BD based on maize-soybean meal with no other additions), E1 (80 mg PFA/kg BD), E2 (125 mg PFA/kg BD), E3 (250 mg PFA/kg of BD) and A (2.5 mg avilamycin/kg BD). Samples from duodenum, ileum and cecum of 14- and 42-day-old broilers were collected and analyzed. In 14-day-old broilers, treatments E2 and E3 had higher (P < 0.01) duodenal mannose than treatments C, E1 and A. Ileal mannose was lower (P < 0.05) in treatment C compared with PFA treatments, and ileal galactose (Gal) was higher (P < 0.01) in treatments E2 and E3 compared with C and A. Polynomial contrast analysis with respect to PFA inclusion level showed that in 14-day-old broilers there was a linear increase (P = 0.001) in duodenal mannose and a quadratic effect (P = 0.038) in duodenal N-acetyl-galactosamine with increasing PFA level. Ileal Gal and mannose increased linearly (P = 0.002 and P = 0.012, respectively) with PFA inclusion level. There were no significant differences between treatments in mucin monosaccharide molar ratios of 42-day-old broilers. However, increasing PFA inclusion level resulted in a linear decrease of ileal fucose (P = 0.021) and cecal N-acetylgalactosamine (P = 0.036). Experimental treatments did not differ (P > 0.05) regarding duodenal villus height (Vh), crypt depth (Cd) and Vh/Cd ratio, irrespective of broiler age and the intestinal segment examined. However, increasing dietary PFA inclusion level showed a pattern of linear increase of duodenal Vh/Cd ratio in 14-day-old broilers and ileal Vh in 42-day-old broilers (P = 0.039 and P = 0.039, respectively). Alcian Blue-Periodic Acid-Schiff (pH 2.5) staining of neutral and acidic mucins showed that the staining intensity of mucus layer in villi was fragment (i.e. tip, midsection and base) dependent, whereas in crypts it was dependent both on intestinal segment (i.e. duodenum, ileum and cecum) and fragment. Finally, mucus layer thickness did not differ (P > 0.05) between treatments, yet a pattern of linear increase (P < 0.05) with PFA inclusion level was observed in the duodenum of 42-day-old broilers. In conclusion, the dietary inclusion level of PFA modulated broiler intestinal mucin composition and morphology. Further studies are required to elucidate the physiological implications of such changes in host-microflora interactions.

In vitro fermentability of dextran, oligodextran and maltodextrin by human gut bacteria.

Anaerobic batch culture fermenters were used for a preliminary screening of the in vitro utilization by human gut microflora of dextran and novel oligodextrans (I, II and III) produced in the University of Reading (UK). Glucose and fructooligosaccharides (FOS) were used as reference carbohydrates. As expected, FOS acted as a good prebiotic in that it selectively increased numbers of bifidobacteria in the early stages of the fermentation. Dextran and oligodextrans each resulted in an enrichment of bifidobacteria in the batch cultures, with high levels of persistence up to 48 h. They also produced elevated levels of butyrate ranging from 5 to 14.85 mmol/l. To more effectively simulate conditions that prevail in different regions of the large intestine, a three-stage continuous culture cascade system was used to study further the fermentation of dextran, a low-molecular-mass oligodextran (IV) and maltodextrin. Oligodextran IV was shown to be the best substrate for bifidobacteria and lactobacilli with steady-state populations of bifidobacteria and lactobacilli being higher in all three vessels of the gut model than the respective populations resulting from dextran and maltodextrin. A maximum difference of 1.9 log was observed in vessel 1 for both bifidobacteria and lactobacilli in the case of dextran fermentation, with 1.4 log and 0.8 log in vessel 3 were the maximum differences for bifidobacteria and lactobacilli when maltodextrin was used as the carbohydrate source. Moreover, dextran and oligodextran appeared to stimulate butyrate production, with a maximum production up to 25.39 mmol/l in vessel 3 when fermenting dextran, followed by 21.70 mmol/l in the case of oligodextran IV and only 12.64 mmol/l in the case of maltodextrin.

A study of dextran production from maltodextrin by cell suspensions of Gluconobacter oxydans NCIB 4943.

This study investigated dextran synthesis from a commercial maltodextrin substrate using cell suspensions of G. oxydans NCIB 4943 as catalysts. Experiments were arranged according to a central composite statistical design. The effects of substrate concentration (10-100 g l-1), cell concentration (0.32-32.0 g wet weight l-1), time of reaction (8-48 h) and pH (3.5-5.5), each at three levels, on dextran yield and dextran molecular weight (MW), were investigated. Response surface methodology was used to assess factor interactions, and empirical models describing the two responses were fitted. Most of the variance in dextran yield could be explained by the fitted model (R2 = 0.96). Dextran yield ranged from 1.21 to 41.69%. The presence of significant negative quadratic effects of cell concentration and time indicated that dextran yield reached a plateau and thus, optimum levels of cell concentration and time could be identified to maximize dextran yield. Dextran MW ranged from 6.6 to 38 kDa and was characterized by the significant interactions of reaction time with substrate concentration and cell concentration. The model, however, could account for only 60% of the variance in dextran MW. Possible reasons for this are discussed.