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     

Original article: In vitro starch digestion and potassium release in sweet potato from Papua New Guinea†

Twenty samples of sweet potato from Papua New Guinea, made up of cultivars 3‐mun, Carot kaukau, Wahgi besta, Nillgai, Baiyer kaukau, and 1‐mun from three provinces, three farmers, and three locations, were subjected to an in vitro starch digestion procedure. Digestion of starch was studied by glucometry, while potassium release was monitored using electrochemistry. The potassium content of the nondigested samples ranged from 4 to 17 mg g^?1 dry solids, while the starch content was from 47 to 80 g per 100 g dry solids and independent of G × E effects. In vitro starch digestibility (2–75 g digested starch per 100 g dry starch) significantly (P < 0.05) varied with time in a nonlinear manner with biphasic digestograms. Potassium release was independent of time in in vitro gastric and pancreatic regions, but more potassium was released during pancreatic than gastric digestion. Results suggest differences in resistant starch and bioavailability of (micro)nutrients that could influence utilisation of sweet potato.     

Effect of phytase inclusion and calcium/phosphorus ratio on the performance and nutrient retention of grower–finisher pigs fed barley/wheat/soya bean meal‐based diets

Two experiments were conducted to evaluate the effects of phosphorus (P) level and calcium (Ca)/total P (tP) ratio on the efficacy of microbial phytase. Experiment 1 examined the effects of P concentration and microbial phytase inclusion on mineral excretion and pig performance, while experiment 2 examined the effects of Ca/tP ratio and microbial phytase inclusion on mineral excretion and pig performance. In experiment 1, nutrient and mineral digestibility (n = 4) and growth performance (n = 12) were determined in pigs individually fed diets containing (T1) 5.5 g kg^?1 tP, 2.3 g kg^?1 available P (aP) and 8.0 g kg^?1 Ca, (T2) 5.5 g kg^?1 tP, 2.3 g kg^?1 aP, 8.0 g kg^?1 Ca and 750 FYT kg^?1 Peniophora lycii phytase, (T3) 4.3 g kg^?1 tP, 1.4 g kg^?1 aP and 8.0 g kg^?1 Ca and (T4) 4.3 g kg^?1 tP, 1.4 g kg^?1 aP, 8.0 g kg^?1 Ca and 750 FYT kg^?1 P lycii phytase. In experiment 2, nutrient and mineral digestibility (n = 4) and growth performance (n = 12) were determined in pigs individually fed diets containing (TT1) 4.3 g kg^?1 tP and 8.0 g kg^?1 Ca, (TT2) 4.3 g kg^?1 tP, 8.0 g kg^?1 Ca and 750 FYT kg^?1 P lycii phytase, (TT3) 4.3 g kg^?1 tP and 5.0 g kg^?1 Ca and (TT4) 4.3 g kg^?1 tP, 5.0 g kg^?1 Ca and 750 FYT kg^?1 P lycii phytase. All diets were formulated, using standard feeding values for the ingredients, to have similar concentrations of digestible energy (DE) and lysine. In experiment 1, pigs offered the low‐P diets had significantly lower P intake (P < 0.001), faecal P excretion (P < 0.05), Ca intake (P < 0.05) and faecal Ca excretion (P < 0.05) compared with pigs given the adequate‐P diets. These pigs also had significantly lower daily gain (P < 0.01), feed intake (P < 0.05) and feed conversion ratio (FCR) (P < 0.05). The inclusion of phytase in both the adequate‐ and low‐P diets increased the digestibility of energy (P < 0.05) and Ca (P < 0.01) but had no effect on pig performance. In experiment 2, lowering the Ca/tP ratio from 1.85:1 to 1.15:1 increased the DE content of the diet (P < 0.05). The inclusion of phytase increased (P < 0.05) the digestibility of protein (0.874 versus 0.840, SEM 0.009) and Ca (0.427 versus 0.380, SEM 0.019) as well as the DE content of the diet (14.47 versus 14.26 MJ kg^?1, SEM 0.073). There was a significant ratio × phytase interaction (P < 0.5) for P digestibility. Microbial phytase significantly increased P digestibility when added to the 1.15:1 ratio diet but had no effect when added to the 1.85:1 ratio diet. The inclusion of microbial phytase increased feed intake (2.16 versus 2.00 kg day^?1, SEM 0.05; P < 0.05) and weight gain (0.893 versus 0.818 kg day^?1, SEM 0.022; P < 0.05). Lowering the Ca/tP ratio resulted in a significant improvement in FCR (2.32 versus 2.40 kg kg^?1, SEM 0.03; P < 0.05). In conclusion, the beneficial effects of microbial phytase supplementation of pig diets are adversely affected by a wide Ca/tP ratio. © 2002 Society of Chemical Industry     

Effect of lactic acid bacteria inoculants on in vitro digestibility of wheat and corn silages

The aim of the study was to determine the effect of 10 sources of lactic acid bacteria (LAB) on dry matter digestibility (DM-D) and neutral detergent fiber digestibility (NDF-D), in various combinations with starch, in vitro. The soluble starch represented a concentrate feed, whereas silage represented feeding only roughage. The DM-D and NDF-D were determined after 24 and 48 h of incubation to represent effective (24 h) and potential (48 h) digestibility. Addition of LAB was both by direct application of the inoculants to rumen fluid (directly fed microbials) and by the use of preinoculated silages. For each feed combination, tubes without added LAB served as controls. The results indicate that, overall, some LAB inoculants applied at ensiling or added directly to the rumen fluid had the potential to increase the DM-D and NDF-D. The major significant inoculant effect on NDF-D was obtained after 24 h of incubation, whereas the effect after 48 h was mainly nonsignificant. The effective inoculants seemed to minimize the inhibitory effect of the starch on NDF-D within 24 h, perhaps by competition with lactate-producing rumen microorganisms.     

Short communication: In vitro rumen gas production and starch degradation of starch-based feeds depend on mean particle size

Our objective was to model the effect of mean particle size (mPS) on in vitro rumen starch degradation (IVSD) and the kinetics of gas production for different starch-based feeds. For each feed, 2 batches of the same grains were separately processed through 2 different mills (cutter or rotor speed mills), with or without different screens to achieve a wide range of mPS (0.32 to 3.31 mm for corn meals; 0.19 to 2.81 mm for barley meals; 0.16 to 2.13 mm for wheat meals; 0.28 to 2.32 mm for oat meals; 0.21 to 2.36 mm for rye meals; 0.40 to 1.79 for sorghum meals; 0.26 to 4.71 mm for pea meals; and 0.25 to 4.53 mm for faba meals). The IVSD data and gas production kinetics, obtained by fitting to a single-pool exponential model, were analyzed using a completely randomized design, in which the main tested effect was mPS (n = 6 for all tested meals, except n = 7 for corn meals and n = 5 for sorghum meals). Rumen inocula were collected from 2 fistulated Holstein dairy cows that were fed a total mixed ration consisting of 16.2% crude protein, 28.5% starch, and 35.0% neutral detergent fiber on a dry matter basis. The IVSD, evaluated after 7 h of rumen incubation, decreased linearly with increasing mPS for corn, barley, wheat, rye, pea, and faba meals, and decreased quadratically with increasing mPS for the other meals. The y-axis intercept for 7-h IVSD was below 90% starch for corn, barley, and rye feeds and greater than 90% for the other tested feeds. The mPS adjustment factors for the rate of rumen starch degradation varied widely among the different tested feeds. We found a linear decrease in starch degradation with increasing mPS for barley, wheat, rye, and pea meals, whereas we noted a quadratic decrease in starch degradation for the other tested meals. Further, we observed a linear decrease in the rate of gas production with increasing mPS in each tested feed, except for pea meal, which had a quadratic relationship. For each 1 mm increase in mPS, the gas production was adjusted by ?0.009 h^?1 for corn, ?0.011 h^?1 for barley, ?0.008 h^?1 for wheat, and ?0.006 h^?1 for faba, whereas numerically greater adjustments were needed for oat (?0.022 h^?1), rye (?0.017 h^?1), and sorghum (?0.014 h^?1). These mPS adjustment factors could be used to modify the starch-based feed energy values as a function of mean particle size, although in vivo validation is required.     

Effects of particle size on physiochemical and in vitro digestion properties of durum wheat bran

In order to promote the potential health benefits of high fibre products, wheat bran is the main focus of the food industry. The physiochemical and in vitro digestion properties of wheat bran containing different particle size were investigated and compared against raw bran samples. Firstly, the bran sample containing superfine particles (11.63 μm) was hydrolyzed by the α-amylase, pepsin, and pancreatin enzymes separately using a single factor and orthogonal test. Secondly, optimized hydrolysis parameters of superfine particles were employed to measure in vitro digestibility of macronutrients in raw, coarse, medium, and superfine bran particles. The maximum degree of hydrolysis obtained via α-Amylase (concentration 10 mg mL⁻¹, pH 6.6, and time 12.5 min) was 55.71%; pepsin (concentration 50 mg mL⁻¹, pH 1.2, and time 9 h) was 82.10%; and pancreatin (concentration 100 mg mL⁻¹, pH 7.0 and time 12 h) was 84.71%, respectively. The highest in vitro digestibility rate of reducing sugar, protein, fat, and soluble fibre content was observed in superfine bran samples to 33.4%, 82.55%, 91.53%, and 21.66%, respectively.     

Inhibition of phenolics on the in vitro digestion of noodles from the view of phenolics release

The inhibition mechanism of buckwheat phenolics on in vitro starch digestion was investigated using extruded noodles with buckwheat starch and phenolic extract (0.50%–2.00%). The cooking quality and reducing sugar released during in vitro digestion were studied, and the extractable phenolic content along digestion was also monitored to reveal a dose–effect relationship between reducing sugar released and the release of phenolics. Noodles containing increased phenolics released less reducing sugar (230–188 mg g⁻¹) during digestion. Cooking and digestion made phenolics more extractable, and most of the phenolics were released at the end of the gastric phase (85.6%–94.8%) compared with during the small intestinal digestion. The IC₅₀ of buckwheat phenolic extract (0.102 mg mL⁻¹) was four times that of acarbose (0.032 mg mL⁻¹). The inhibitory mechanism was further analysed using molecular docking, in which the activity of α-amylase was inhibited by phenolics that bind with active sites of α-amylase through hydrogen bonds and hydrophobic interaction. Phenolics interacting with starch and the released phenolics can both explain the reduction in starch digestion.     

高温蒸煮-复合酶法制备绿豆皮可溶性膳食纤维及体外降血糖作用研究

以绿豆皮为原料,采用高温蒸煮-复合纤维素酶和木聚糖酶法提取可溶性膳食纤维,探讨不同因素对得率的影响,并探究其体外降血糖作用。结果表明,最佳条件为料液比1∶30 g/mL、蒸煮温度120℃、蒸煮45 min、木聚糖酶0.75%、纤维素酶1.5%、酶解120 min、温度50℃,得率20.12%;高温蒸煮-复合酶处理后,持水力、持油力、膨胀力分别提升了49.86%、136.96%、103.54%;葡萄糖扩散抑制能力在60 min时提升了68.92%,葡萄糖吸附力在可溶性膳食纤维浓度为0.5%时提升了112.68%,α-淀粉酶最大抑制率提升了54.41%;动力学实验表明,可溶性膳食纤维处理前后对α-淀粉酶抑制类型均为非竞争型抑制。     

大米主食制品中污染物镉的体外消化释放研究

对含污染物镉的大米主食样品米饭和米线进行体外模拟消化,采用石墨炉原子吸收分光光度法(GF-AAS)对样品中镉进行定量检测。口腔阶段镉释放率:生大米原料粉(34.85%)米线(5.69%)米饭(0%);胃阶段释放率:米饭(74.51%)米线(71.62%)生大米原料粉(0%);小肠阶段中的最大释放率为:4 h时生大米原料粉(60.19%)7 h时米线(45.35%)5 h时米饭(37.06%)。结果表明:不同大米主食样品在不同消化阶段中污染物镉的消化释放有显著差异,已消化释放出的镉在不同时间和消化部位还会被重新吸附结合,使镉释放率增加又降低;在小肠1~3 h消化时间下,米饭中镉消化释放率显著大于米线样品,而小肠消化3h后,则相反。该研究结果可作为大米及制品中污染物镉生物可给性的研究基础,为进一步合理食用和风险暴露评估提供参考。     

Technical note: Precision and accuracy of in vitro digestion of neutral detergent fiber and predicted net energy of lactation content of fibrous feeds

The objective of this study was to test the precision and agreement with in situ data (accuracy) of neutral detergent fiber degradability (NDFD) obtained with the rotating jar in vitro system (Daisy^II incubator, Ankom Technology, Fairport, NY). Moreover, the precision of the chemical assays requested by the National Research Council (2001) for feed energy calculations and the estimated net energy of lactation contents were evaluated. Precision was measured as standard deviation (SD) of reproducibility (S_R) and repeatability (S_r) (between- and within-laboratory variability, respectively), which were expressed as coefficients of variation (SD/mean × 100, S_R and S_r, respectively). Ten fibrous feed samples (alfalfa dehydrated, alfalfa hay, corn cob, corn silage, distillers grains, meadow hay, ryegrass hay, soy hulls, wheat bran, and wheat straw) were analyzed by 5 laboratories. Analyses of dry matter (DM), ash, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) had satisfactory S_r, from 0.4 to 2.9%, and S_R, from 0.7 to 6.2%, with the exception of ether extract (EE) and CP bound to NDF or ADF. Extending the fermentation time from 30 to 48 h increased the NDFD values (from 42 to 54% on average across all tested feeds) and improved the NDFD precision, in terms of both S_r (12 and 7% for 30 and 48 h, respectively) and S_R (17 and 10% for 30 and 48 h, respectively). The net energy for lactation (NE_L) predicted from 48-h incubation NDFD data approximated well the tabulated National Research Council (2001) values for several feeds, and the improvement in NDFD precision given by longer incubations (48 vs. 30 h) also improved precision of the NE_L estimates from 11 to 8%. Data obtained from the rotating jar in vitro technique compared well with in situ data. In conclusion, the adoption of a 48-h period of incubation improves repeatability and reproducibility of NDFD and accuracy and reproducibility of the associated calculated NE_L. Because the in vitro rotating jar technique is a simple apparatus, further improvement would probably be obtained by reducing the laboratory differences in rumen collection procedures and type of animal donors, which, however, reflect practical conditions.     

沙葱总黄酮提取工艺优化及其体外抗氧化、抗菌作用

在单因素试验的基础上,采用响应面方法对纤维素酶辅助提取沙葱总黄酮的工艺参数进行优化,得到最优工艺条件为提取时间4 h、提取温度39 ℃、体系pH 4.3,沙葱总黄酮提取量为5.48 mg/g。通过体外抗氧化及抗菌实验得出,此条件下提取所得沙葱总黄酮具有较好的总还原能力、体外清除DPPH自由基及清除羟自由基的能力,对沙门氏菌具有较好的抑制作用,对大肠杆菌和金黄色葡萄球菌的抑制作用较弱,对绿脓杆菌无抑制作用。     

Development of a three‐tier in vitro system,using Caco‐2 cells,to assess the effects of lactate on iron uptake and transport from rye bread following in vitro digestion

A three‐tier Caco‐2 cell system was developed to assess simultaneously iron dialysability, uptake and transport across the Caco‐2 monolayer from an in vitro digested food matrix. The effect of lactate (0–200 mmol L⁻¹) on iron absorption from rye bread subjected to simulated peptic (pH 5.5) and pancreatic digestion (pH 6.5) was investigated to model absorption pre and post the sphincter of Oddi. Lactate increased dialysability (11.8%, P < 0.05) in peptic digests whereas it reduced it in pancreatic digests (4.9%, P < 0.001). Iron uptake from the peptic digests was in the region of 39–76 pmol mg⁻¹ protein whereas it decreased from 281 to 51 pmol mg⁻¹ protein in pancreatic digests. Iron transport was calculated for the peptic digests from [¹⁴C]polyethylene glycol movement and only at 200 mmol L⁻¹ lactate was there any detectable transcellular transport (180 pmol mg⁻¹ protein, P < 0.05). Iron absorption was positively correlated to dialysable iron for both digests (R² = 0.48 and 0.41, respectively, P < 0.01) and the effect of lactate was therefore associated mainly with iron bioaccessibility. The three‐tier system showed the potential to obtain detailed insight into each step involved in iron transport across the monolayer from a food mixture. Copyright © 2006 Society of Chemical Industry     

Technical note: Evaluation of a novel enzymatic method to predict in situ undigested neutral detergent fiber of forages and nonforage fibrous feeds

The purpose of this study was to optimize the conditions of a previously proposed enzymatic method used to estimate in situ undigested neutral detergent fiber (uNDF). We used a multi-step enzymatic approach, in which samples were first solubilized in NaOH solutions as a preincubation (PreInc) phase. After rinsing, samples were incubated (24 h at 39°C) in a buffered solution (pH 6) containing hemicellulase, cellulase, and Viscozyme L enzymes (Sigma-Aldrich s.r.l., Milan, Italy), followed by incubation (24 h at 39°C) in a buffered solution (pH 5) containing xylanase. Two sets of experiments were performed: a calibration trial (that tested different PreInc conditions on 9 selected forages) and a validation trial (that verified the results by testing multiple samples of 6 different forage types and a group of fibrous by-products). In the calibration trial, samples (300 mg in Ankom F57 filter bags; Ankom Technology Corp., Fairport, NY) were preincubated at 39°C in a 0.1 M NaOH solution for 90, 180, or 240 min, or in 0.2, 0.5, 1.0, or 2.0 M NaOH solution for 90 min. The results indicated that the best PreInc method, in terms of intra-laboratory repeatability and estimation of reference in situ values, was 90 min in a 0.2 M NaOH solution. Thus, we used this PreInc condition to determine enzymatic uNDF of 257 samples in the validation trial. Although the selected method generally had good accuracy in predicting in situ uNDF, inconsistencies were noted for certain forage types. Overall, when enzymatic uNDF was used to predict the in situ uNDF of all samples, the regression was satisfactory (intercept = 7.098, slope = 0.920, R² = 0.73). The regression models developed for alfalfa hays, corn silages, and small grain silages had also acceptable regression performances and mean square error of prediction (MSEP) values, and the main sources of MSEP variation were error due to incomplete (co)variation and random error. Even when R² values were >0.70, the MSEP value of the regression model for grass hays was 149.55, and that for nonforage fibrous feeds was 155.16. Although enzymatic uNDF partially overestimated the in situ uNDF, particularly in grass silages, the proposed procedure seems to be promising for accurately predicting in situ uNDF, because it generally had good repeatability and provided satisfactory estimates of in situ uNDF.     

The effect of cellulose crystallinity on the in vitro digestibility and fermentation kinetics of meadow hay and barley,wheat and rice straws

The effect of cellulose crystallinity on in vitro digestibility (IVD) and fermentation kinetics was investigated in samples of meadow hay and barley, wheat and rice straws. A saturated solution of potassium permanganate was used to isolate the celluloses, and their crystallinity was evaluated in a Fourier transform infrared spectrometer as the ratio of the observed transmittance at two distinct wave frequencies . IVD was determined after 48 h of incubation, and the kinetics of fermentation was studied with fully automated gas production equipment. Despite significant differences (P < 0.05), crystallinity showed low variation (0.30–0.42) among celluloses and correlated positively with IVD (P < 0.05). Although positively correlated with maximal gas production (r = 0.91) and rates of fermentation, IVD (averaging 784 g kg^?1 organic matter (OM)) was also low for all samples as compared with the usually referred values for isolated celluloses. The lowest means were observed for meadow hay and rice straw. The cumulative gas production profiles were well described by a monophasic model (r² = 0.997, RSD (residual standard deviation) = 8.367), but all the curves had a lag phase varying from 3 to 6 h. Cellulose isolated from rice straw showed the lowest maximal gas production (366 ml g^?1 OM) and highest times to reach half of the maximal gas production and maximal rate. Transmission electron microscopy (TEM) of two cellulose samples showing considerable gas production at highest rates as compared with cellulose isolated from rice straw that provided the lowest gas production at the lowest rate revealed generalised bacterial colonisation, the presence of glycocalyx fibres and cell erosion in all samples. Although samples collected after 12 h of fermentation appeared to present lower microbial attack as compared with those incubated for 24 h, TEM did not explain the observed differences in the data. Since crystallinity, IVD, gas production and rates of fermentation were shown to be associated with the nutritional availability of cellulose, further research dealing with extreme values of cellulose crystallinity may be important. © 2003 Society of Chemical Industry