Estimation of the Bioavailability of Iron and Phosphorus in Cereals using a Dynamic In Vitro Gastrointestinal Model

A recently developed in vitro gastrointestinal model was evaluated for the estimation of the bioavailability of Fe and phosphorus and its correlation with biovailability in vivo. In vitro experiments were carried out without and with phytase supplementation (750 FTU kg^-1 feed) using rapeseed, sunflowerseed, wholewheat and white wheat flour. Phytase addition during in vitro digestion of rapeseed and sunflowerseed resulted in markedly increased dialysability of iron (67% and 20%) and phosphorus (31% and 66%). The release of free phosphorus during digestion of wholewheat and white wheat flour in the in vitro gastrointestinal model was observed to be correlated with the endogenous phytase activity in wheat. Comparison with different in vivo studies revealed that the in vitro gastrointestinal model could be used for a relative estimation of the bioavailability of Fe and phosphorus. © 1997 SCI.     

The degradation of phytate by microbial and wheat phytases is dependent on the phytate matrix and the phytase origin

BACKGROUND: Phytases increase utilization of phytate phosphorus in feed. Since wheat is rich in endogenous phytase activity it was examined whether wheat phytases could improve phytate degradation compared to microbial phytases. Moreover, it was investigated whether enzymatic degradation of phytate is influenced by the matrix surrounding it. Phytate degradation was defined as the decrease in the sum of InsP₆ + InsP₅. RESULTS: Endogenous wheat phytase effectively degraded wheat InsP₆ + InsP₅ at pH 4 and pH 5, while this was not true for a recombinant wheat phytase or phytase extracted from wheat bran. Only microbial phytases were able to degrade InsP₆ + InsP₅ in the entire pH range from 3 to 5, which is relevant for feed applications. A microbial phytase was efficient towards InsP₆ + InsP₅ in different phytate samples, whereas the ability to degrade InsP₆ + InsP₅ in the different phytate samples ranged from 12% to 70% for the recombinant wheat phytase. CONCLUSION: Wheat phytase appeared to have an interesting potential. However, the wheat phytases studied could not improve phytate degradation compared to microbial phytases. The ability to degrade phytate in different phytate samples varied greatly for some phytases, indicating that phytase efficacy may be affected by the phytate matrix. Copyright © 2011 Society of Chemical Industry     

Effects of exogenous fibrolytic enzymes on epiphytic microbial populations and in vitro digestion of silage

Epiphytic microbial populations, reducing sugar (RS) concentrations and in vitro fermentation were measured in unsterilised and sterilised barley silage and corn silage treated with an exogenous enzyme preparation. Enzyme treatments comprised spraying silages (10 ml kg^?1 DM) with a xylanase/β‐glucanase enzyme preparation or with water or autoclaved enzyme (controls). In Experiment 1, autoclaving the silages increased (P < 0.05) concentrations of RS present 24 h after treatment. Enzymes increased (P < 0.05) RS in both fresh and autoclaved silages, more so (P < 0.05) with autoclaving than without. Autoclaved enzymes did not affect RS concentrations relative to the (water) controls. Aerobic exposure of corn silage numerically increased microbial numbers; no microbial viability was detected in autoclaved silages. Enzymes increased (P < 0.05) total bacterial counts in all silage types, and this effect was more pronounced on aerobically exposed silage. In Experiment 2, RS concentrations were determined 0 and 24 h after enzyme treatment of silages unsterilised or sterilised with ethylene oxide (EO). Irrespective of EO or silage type, RS concentrations were higher (P < 0.05) 24 h after enzyme treatment than immediately after (0 h). In enzyme‐treated silages, 24 h RS concentrations were higher (P < 0.05) with EO than without. Reducing epiphytic microbiota by sterilisation conserved enzyme‐liberated RS in the silages. Aerobic exposure before applying enzymes enhanced RS‐associated increases in microbial numbers. Enzymes effectively released RS from silages, but utilisation of the RS by inherent epiphytic micro‐organisms may limit their availability to the ruminant. By releasing RS, exogenous enzymes may encourage silage deterioration if the interval between treatment and feeding is excessive. During in vitro incubation of freeze‐dried silages (Experiment 3), incorporation of ¹⁵N into microbial N was decreased by enzyme applied to fresh silage (before drying), but increased by enzyme applied after the silage had been dried. Moisture level of feeds and epiphytic microbial populations may influence the effectiveness of enzyme treatment for enhancing utilisation of feeds by ruminants. For the Department of Agriculture and Agri‐Food, Government of Canada. © Minister of Public Works and Government Services Canada 2002. Published for SCI by John Wiley & Sons, Ltd     

Comparative evaluation of the efficacy of cereal and microbial phytases in growing pigs fed diets with marginal phosphorus supply

Two experiments with a total of 76 growing pigs (average initial body weight 16.6 kg) were conducted to compare the efficacy of cereal phytases (wheat and rye) and supplemented microbial phytase (Natuphos®). Using the slope ratio technique, the dose–response relationship between five levels of phytase (0, 50, 100, 150 and 200 U kg^?1) and the apparent absorption of phosphorus (P) within each source of phytase was calculated. Graded phytase levels in the diets were obtained by adding increasing amounts of microbial phytase or phytase‐containing wheat (Exp 1) or rye (Exp 2) to phytase‐inactivated basal diets at the expense of phytase‐inactivated wheat (Exp 1) or rye (Exp 2). Except for wheat phytase, addition of phytase to the basal diets increased (P < 0.05) apparent P absorption, with microbial phytase being more efficient (P < 0.05) than cereal phytase. There were no significant differences in apparent P absorption between the wheat‐ or rye‐based diets when either microbial or cereal phytases were supplemented from 0 to 200 U kg^?1. It could be derived from the results of this study, by means of regression analysis, that the efficacy of cereal phytases was 40% compared to microbial phytase. © 2002 Society of Chemical Industry     

Effect of endo‐xylanase‐containing enzyme preparations and laccase on the solubility of rye bran arabinoxylan

Three commercial enzyme preparations with endo‐xylanase activity, namely Bio‐Feed Wheat, Bio‐Feed Plus and Grindamyl H 640, and laccase have been tested for their effects on the solubilisation of arabinoxylan (AX) in rye bran or autoclaved rye bran. Autoclaving efficiently increased the availability of AX for enzymatic degradation. Both Bio‐Feed Wheat (a monocomponent enzyme) and Bio‐Feed Plus (a multicomponent preparation with different enzymatic activities) efficiently degraded the autoclaved rye bran AX into lower‐molecular‐weight fragments. As much as 70% of the xylose residues and 58% of the arabinose residues in the autoclaved bran were soluble after treatment with Bio‐Feed Plus; the weight—average molecular weight of the detectable portion of these soluble polymers was 104 000 Da. Grindamyl H 640 solubilised only a small fraction of the AX in autoclaved rye bran; the molecular weight of these soluble fragments was higher than that of those released by the Bio‐Feed xylanases. Addition of laccase during treatment with Bio‐Feed Wheat or Grindamyl H 640 decreased the yield of water‐soluble AX. © 2003 Society of Chemical Industry     

Fibrolytic potential of anaerobic fungi (Piromyces sp.) isolated from wild cattle and blue bulls in pure culture and effect of their addition on in vitro fermentation of wheat straw and methane emission by rumen fluid of buffaloes

BACKGROUND: Ten isolates of anaerobic fungi of Piromyces genus from wild cattle and blue bulls (five isolates from each host species) were evaluated for their fibrolytic ability in pure culture, their suitability for use as a microbial additive in buffaloes and their effect on methane emission. RESULTS: In pure culture, only two out of five isolates from wild cattle degraded wheat straw efficiently, whereas all five isolates from wild blue bulls did. Isolate CF1 (from cattle) showed the highest apparent digestibility (53.4%), true digestibility (70.8%) and neutral detergent fibre digestibility (75.0%) of wheat straw after 5 days of incubation. When added to buffalo rumen fluid, all five isolates from cattle increased (P < 0.05) in vitro apparent digestibility of wheat straw compared with the control (received autoclaved culture), but all five isolates from blue bulls failed to influence in vitro digestibility of wheat straw. Isolate CF1 showed the highest stimulating effect on straw digestion by buffalo rumen fluid microbes and increased apparent digestibility (51.9 vs 29.4%, P < 0.05), true digestibility (57.9 vs 36.5%, P < 0.05) and neutral detergent fibre digestibility (51.5 vs 26.9%, P < 0.05) of wheat straw compared with the control after 24 h of fermentation. There were also significant increases in fungal count and enzyme activities of carboxymethylcellulase and xylanase in the CF1‐added group compared with the control group. Gas and methane production g^?1 truly digested dry matter of straw were comparable among all groups including the control. CONCLUSION: Wild cattle and blue bulls harbour some anaerobic fungal strains with strong capability to hydrolyse fibre. The fungal isolate CF1 has high potential for use as a microbial feed additive in buffaloes to improve digestibility of fibrous feeds without increasing methane emission per unit of digested feed. Copyright © 2010 Society of Chemical Industry     

Influence of exogenous enzyme supplementation on energy utilisation and nutrient digestibility of cereals for broilers

The influence of a microbial phytase, produced by solid‐state fermentation, on the apparent metabolisable energy and ileal digestibility of phosphorus, nitrogen and starch in sorghum, maize, wheat and barley was examined using 4‐week‐old broilers. For wheat and barley, the influence of phytase, individually or in combination with glycanases, was also evaluated. Microbial phytase improved (p < 0.05) apparent ileal phosphorus digestibility in all cereals. Phytase supplementation improved (p < 0.05) the apparent metabolisable energy of maize and barley by 2.6 and 7.8%, respectively. Numerical improvements in apparent metabolisable energy were observed in sorghum (1.9%) and wheat (2.1%), but were not statistically significant (p > 0.05). Further improvements (p < 0.05) in the apparent metabolisable energy of wheat and barley were observed when the phytase was combined with glycanases. However, the observed improvements in apparent metabolisable energy were not always associated with enhanced ileal digestibility of protein and starch. Copyright © 2004 Society of Chemical Industry     

Peniophora lycii phytase is stabile and degrades phytate and solubilises minerals in vitro during simulation of gastrointestinal digestion in the pig

BACKGROUND: Microbial phytases (EC 3.1.3) are widely used in diets for monogastric animals to hydrolyse phytate present in the feed and thereby increase phosphorus and mineral availability. Previous work has shown that phytate solubility is strongly affected by calcium in the feed and by pH in the gastrointestinal (GI) tract, which may have an effect on phytase efficacy. An in vitro model simulating the GI tract of pigs was used to study the survival of Peniophora lycii phytase and the effect of the phytase on phytate degradation, inositol phosphate formation and mineral solubilisation during in vitro digestion of a 30:70 soybean meal/maize meal blend with different calcium levels. RESULTS: The phytase retained 76 and 80% of its initial activity throughout the gastric in vitro digestion. Total phytate hydrolysis by P. lycii phytase was in the same range at total calcium levels of 1.2 and 6.2 mg g^?1 dry matter (DM), despite very large differences in phytate solubility at these calcium levels. However, at 11.2 and 21.2 mg Ca g^?1 DM, phytate hydrolysis was significantly lower. The amount of soluble mineral was generally increased by P. lycii phytase. CONCLUSION: Stability of P. lycii phytase during gastric digestion was not found to be critical for phytate hydrolysis. Furthermore, original phytate solubility was not an absolute requirement for phytate degradation; phytate solubility seemed to be in a steady state, allowing insoluble phytate to solubilise as soluble phytate was degraded. This is new and interesting knowledge that adds to the current understanding of phytate–phytase interaction. Copyright © 2007 Society of Chemical Industry     

Impact of arabinoxylan with different molecular weight on the thermo‐mechanical,rheological, water mobility and microstructural characteristics of wheat dough

The aim of this study was to investigate the effects of arabinoxylan with different molecular weight on the wheat dough thermo‐mechanical, rheological, microstructural and water mobility properties. Arabinoxylan was extracted from wheat bran and hydrolysed by endo‐1,4‐β‐xylanase (EC 3.2.1.8 from Trichoderma reesei, 10 000 U g^?1) for 2 min (AX_M) and 10 min (AX_L), respectively. The addition of hydrolysed arabinoxylan AX_L increased the stability time, decreased the setback value of wheat dough and enhanced the values of storage modulus (G′) and loss modulus (G″), while unhydrolysed arabinoxylan (AX_H) reduced these values. Meanwhile, unhydrolysed arabinoxylan increased T₂ relaxation time while hydrolysed arabinoxylan AX_L decreased T₂₁ and T₂₂. Confocal laser scanning microscope (CLSM) results showed that the addition of hydrolysed arabinoxylan AX_L promoted the formation of a more compact and continuous protein network in wheat dough. These results revealed that compared with high molecular weight arabinoxylan, hydrolysed arabinoxylan could improve the rheological properties and processing properties of wheat dough by enhancing the interaction among water molecules, starch and gluten in wheat dough.     

In-vitro and in-vivo dephosphorylation of rapeseed meal by means of phytate-degrading enzymes derived from Aspergillus Niger

A meal of ‘double low’ rapeseed (var ‘Jantar’) was subjected to phytate hydrolysis using enzyme preparations derived from a mycelium of Aspergillus niger which contained phytase (EC 3.1.3.8) and acid phosphatase (EC 3.1.3.2) activities. The complete conversion of myo-inositol hexa- and pentaphosphates present in rapeseed meal to lower phosphate esters of myo-inositol was accomplished at 40°C, a pH value of 4.5, phytase dosage (in phytase units (PhytU)) 0.1 PhytU g^?1 accompanied by acid phosphatase activity 37.1 units g^?1, in 1 h. Under these conditions, complete dephosphorylation was observed in 4 h. Decreasing the pH value to 3.0 caused a rise in the amount of inorganic phosphorus released, while increasing to 5.5 resulted in substantial reduction in the reaction rate. Purification of phytase to a specific activity 0.375 PhytU mg^?1 of protein exhibited a negative influence upon the yield of rapeseed dephosphorylation. The substitution of calcium phosphate for a preparation of phytase in feed containing rapeseed meal did not cause significant differences in the body weight gain or in tibia mineralisation of broilers (Gains galus, ‘Astra B’).     

Effects of arabinoxylan solubilization on wort viscosity and filtration when mashing with grist containing wheat and wheat malt

Arabinoxylans are partially water-extractable, high-molecular-weight polymers that contribute to the problems of viscosity and membrane filterability during beer brewing. These problems are more pronounced when wheat and wheat malt are used as adjuncts due to their higher arabinoxylan contents and higher molecular weights. This paper aimed at investigating the effects of mashing temperature, time, grist size and liquor:grist ratio on the solubilization of arabinoxylans. Results indicated that increasing the mashing temperature generally increased the amount of arabinoxylans released into the wort. When greater proportions of wheat or wheat malt were used as adjunct, higher arabinoxylan contents in the final wort were observed. The more finely ground the grist, the more were arabinoxylans released into the wort. When more diluted mashes were used, more efficient solubilization of arabinoxylans was observed. The effects of arabinoxylan content and β-glucan content on the wort viscosity were also examined using a General Linear Model (GLM). There was a good correlation (R² = 0.98) between wort viscosity and its arabinoxylan and β-glucan contents.     

Calcium Additives and Sprouted Wheat Effects on Phytate Hydrolysis in Whole Wheat Bread

Whole wheat bread loaves were subjected to treatments of different fermentation periods, different sources and levels of calcium, and the addition of sprouted wheat. Phytate losses increased with increased fermentation time. Increasing the calcium level inhibited phytate hydrolysis when the calcium was provided by nonfat dry milk, CaCl₂, or nonfat yogurt, whereas phytate hydrolysis in loaves supplemented with CaCO₃ remained nearly constant. Milk-derived calcium exerted the greatest inhibition of phytate hydrolysis. The addition of sprouted wheat decreased absolute phytate losses. A comparison of phytate losses in yeasted vs nonyeasted loaves suggested that endogenous wheat phytase was quantitatively more important than yeast phytase during breadmaking.     

Wheat Phosphorus Availability: 1—In VitroStudy; Factors Affecting Endogenous Phytasic Activity and Phytic Phosphorus Content

Phytasic activity and phytic P content, which are important factors in determining the availability of P, were measured in 56 wheat samples. The different agronomic and genetic factors which could have an influence on these two variables were studied, specifically N and/or P fertilisation, date of harvest, preharvest sprouting and variety of French wheat. Phytasic activity ranged from 206 to 775mUg⁻¹, with an average of 508mUg⁻¹ and a standard deviation of 109mUg⁻¹. Only the variety of wheat appeared as a significant factor explaining the endogenous phytasic activity ( P =0·006). The phytic P content varied between 0·92 and 2·80gkg⁻¹ DM, with an average of 2·18gkg⁻¹ and a standard deviation of 0·35gkg⁻¹ DM. None of the factors studied significantly affected the phytic P content of the wheat. This content was correlated with the total P content ( r =0·56; P< 0·05). The activity of the endogenous phytase was independent of the quantity of its substrate, the phytic phosphorus of the kernels of wheat.     

Supplementation of alkaline phytase (Ds11) in whole-wheat bread reduces phytate content and improves mineral solubility

Abstract: In this study, alkaline phytase was added to whole‐wheat bread and the phytate content and mineral profiles were compared to commercially available acidic phytase. At neutral pH, some phytate (approximately 20%) was degraded by endogenous phytase in wheat flour, while 40% of phytate was hydrolyzed by alkaline phytase DS11 and a 35% reduction was observed with acidic phytase. Most of the enzymatic activity occurred during the proofing stage, and the rate of reaction depended on pH. DS11 phytase effectively degraded the phytate level within a 30 min treatment at pH 7; however, at least 60 min was needed with acidic phytase to achieve the same hydrolysis level. Mineral profiles were also dramatically affected by the phytate reduction. The biggest increase was observed in Fe²⁺ by the phytase treatment. The Fe²⁺ content increased 10‐fold at pH 7 and 8‐fold at pH 5 with alkaline phytase DS11. Alkaline phytase DS11 was shown to be effective at phytate reduction in whole‐wheat bread preparation. Additionally, phytate degradation enhanced the mineral availability of bread.     

Hydrolysis of galactooligosaccharides by commercial preparations of α-galactosidase and β-fruetofuranosidase: Potential for use as dietary additives

In vitro and in vivo studies were conducted with six commercial enzyme preparations (SP249, Energex, Rohament CW, Novozyme 230 and crude α -galactosidase) to determine their effectiveness in hydrolysing galactooligosaccharides from soya bean and canola meal in the gastrointestinal tract of poultry. The use of the enzyme invertase to enhance galactoside hydrolysis was also studied. A wide range of α -galactosidase activity was observed in vitro, with crude α-galactosidase from Mortirella vinacea and Novozyme 230 preparation showing the highest activity values of 4.3 and 1.5 nkat mg^?1, respectively. All preparations with the exception of crude α-galactosidase showed invertase activity which is known to convert raffinose and stachyose to the corresponding di-and trisaccharide, melibiose and manninotriose. Although the activity of invertase was highest on sucrose, the Novozyme 230 preparation showed activity values of 4.2 and 2.3 nkat mg^?1 toward raffinose and stachyose substrates, respectively. De novo synthesis of raffinose was observed when soya bean meal, canola meal or pure sucrose and galactose were incubated with certain enzyme preparations (ie Energex). In general, preparations possessing hydrolytic activity towards galactooligosaccharides showed very little synthesis of raffinose while preparations capable of generating raffinose were very weak in the hydrolysis of galactooligosaccharides. The best result in terms of galactooligosaccharide in vitro hydrolysis of canola and soya bean meal was obtained with a combination of α-galactosidase and invertase. In the in vivo study with caecectomised hens, hydrolysis of galactooligosaccharides averaged 88% when crude α-galactosidase (2 g kg^?1) and invertase (1 g kg^?1) were added to laying, hen diet containing 200 g soya bean meal per kilogram. A problem identified in the current study was that minerals such as calcium phosphate and calcium carbonate common in poultry diets inhibit the hydrolysis activity of α-galactosidase, indicating that high levels of activity would be required to yield a response in practical poultry feeding.     

Effect of tannic acid on in vitro enzymatic hydrolysis of some protein sources

The pH‐stat system has been used to assess the effect of tannic acid (TA) on solubility and in vitro enzyme hydrolysis of different proteins. Added TA (from 10 to 50 g kg^?1) decreased the extent of hydrolysis of bovine serum albumin. Enzymic hydrolysis of casein, pea meal, soybean meal, and haemoglobin (HB) was increased, as measured by total amino acids released and by the degree of hydrolysis. SDS‐PAGE confirmed the results of the in vitro enzymatic hydrolysis. These findings suggest that, under in vitro conditions, when simulating the gastrointestinal environment of domestic mammals, the negative effects of TA described from in vivo experiments are not necessarily due to reduced hydrolysis of proteins. Copyright © 2003 Society of Chemical Industry     

In vitro starch digestion kinetics of diets varying in resistant starch and arabinoxylan compared with in vivo portal appearance of glucose in pigs

The current study was undertaken to investigate the relationship between the in vitro starch digestion kinetics and the in vivo portal glucose appearance in pigs used as models for humans. In vivo data were obtained from a previous study where the portal glucose appearance was obtained from six catheterised pigs equipped with permanent catheters in an artery and the portal vein and with a flow probe attached to the portal vein for monitoring the blood flow rate. Three experimental diets were studied — a low dietary fibre (DF), western-style diet (WSD) and two high-DF diets containing resistant starch (RSD) or arabinoxylan (AXD). A modified Englyst-assay involving gradual glucose hydrolysis over a time frame of 6 h was used in vitro. The in vitro starch digestion kinetics was modelled using a mechanistic growth model (R² > 0.995), whereas the in vivo data were better described by a sigmoid Gompertz model (R² > 0.997). The estimated plateau values were higher in vitro than in vivo but the diets were similarly ranked; ~ 95% for AXD and WSD and 81.8% for RSD in vitro and ~ 86% and 76.6% for the same diets in vivo. The rate of glucose release in vitro was much faster than the portal glucose appearance in vivo (0.0347–0.0705 versus 0.0136–0.0197% starch/min) with the starch in RSD being the most slowly degradable. This difference was most likely an effect of gastric retention. In conclusion, the in vitro method ranked the three diets in a similar relative manner as in vivo but the rate of glucose release was much faster in vitro than in vivo. It was only when the starch structure set the limit for the starch hydrolysis, however, that similar relative results were obtained.     

Production of phytase in a low phosphate medium by a novel yeast Candida krusei

A yeast strain producing high levels of phytase was isolated from soil and identified as Candida krusei. The phytase was located on the yeast cell wall and was a glucanase-extractable protein. The phytase production was controlled by the phosphate concentration in the medium used. The maximum production of phytase occurred in a medium containing 0.5 mg of phosphorus per 100 ml, and most of the cells were ellipsoid-shaped and did not exhibit budding. Increasing the concentration of phosphorus in the medium to more than 5 mg of phosphorus per 100 ml caused inhibition of phytase production and 90% of the cells exhibited budding. On the other hand, transferring cells grown in the high-phosphate medium into a phosphate-free one derepressed the phytase production. For example, transferring cells grown in 2 mg of phosphorus per 100 ml into the phosphate-free medium, enhanced the total phytase activity up to 5.5-fold that in the medium containing 0.5 mg of phosphorus per 100 ml. The phytase showed two optimum pHs of 2.5 and 5.5, an optimum temperature of 40 degrees C and the K(m) value for Na-phytate was 0.03 mM. Using in vitro experiments that simulated the conditions of the digestive tract, 50-80% phosphorus was liberated from different plant samples (wheat bran, rice bran and feeds) by the strain.     

Integration of ileum cannulated pigs and in vitro fermentation to quantify the effect of diet composition on the amount of short‐chain fatty acids available from fermentation in the large intestine

Using cannulated pigs and a standardised in vitro fermentation system the effect of diet and non‐starch polysaccharides (NSP) on the amount of energy available from microbial fermentation in the large intestine could be predicted. The available energy was calculated from the amounts of short‐chain fatty acids (SCFA) produced. Three diets were investigated: a low fibre diet based essentially on wheat flour (56 g NSP kg⁻¹ feed) and two high fibre diets with added oat bran (93 g NSP kg⁻¹ feed) or wheat bran (102 g NSP kg⁻¹ feed). Colonic fermentation was estimated by in vitro fermentation of freeze‐dried ileal effluent collected from cannulated pigs. The in vitro fermentation method was optimised to use 10 g ileum content litre⁻¹ incubated at pH 6.0 in a fermentor containing faecal slurry consisting of anaerobic mineral salts medium and 50 g litre ⁻¹ faeces from pigs fed the same diets as the cannulated pigs. The results demonstrate that it is very important to compensate for the faecal SCFA contribution when calculating the amount of SCFA produced from ileal digesta during in vitro fermentation. The amount of NSP digested in vitro was compared with data obtained from in vivo studies and there was a good agreement between in vivo and in vitro data. We concluded that the integrated in vivo–in vitro method is a valuable technique to estimate the effect of diet and NSP on the amount of SCFA produced in the large intestine and when fed the three diets the microbial fermentation in the large intestine provided between 2.4–6.4% of the total available energy. © 1999 Society of Chemical Industry     

Lactic Fermentation of Non-Tannin and High-Tannin Cereals: Effects on In Vitro Estimation of Iron Availability and Phytate Hydrolysis

The effect on iron availability estimated in vitro and phytate hydrolysis was investigated in non-tannin and high-tannin cereals, lactic fermented as flour/water slurries or gruels. A natural starter culture initiated fermentation and addition of germinated flour and phytase in the fermentation process was tested. Lactic fermentation of nontannin cereals with added flour germinated sorghum seeds or wheat phytase increased iron solubility from about 4% up to 9 and 50%, respectively. Soaking flour in water before adding starter culture had a similar effect. The increase in soluble iron was strongly related to enzymatic deeradation of phytate (p<0.001). The reduction of inositol hexa- and pentaphosphates was about 50% with added germinated flour. Reduction was > 90% after soaking the flour prior to fermentation and almost complete with 50 mg phytase added. High-tannin cereals showed a minor increase in soluble iron after fermentation, ascribed to the inhibitory effect of tannins (both on iron solubility and on enzymatic hydrolysis of phytate). Lactic-fermented cereal foods have a potential in developing countries to improve iron nutrition.