Advances in the in vitro digestion and fermentation of polysaccharides

In vitro digestion models are widely used to study the structural changes, digestion and release of food components under simulated gastrointestinal conditions. As compared to the in vivo digestion tests, the in vitro digestion reflects the digestion and utilisation of food after ingestion and has the advantages of being time consuming, inexpensive, reproducible and free from moral and ethical restrictions. This study reviewed the current research studies on the in vitro simulated digestion of polysaccharides conducted in the last 5 years and focused on the oral, gastric and intestinal digestion models, with the aim of providing a basis for the further testing of changes in the content, structure and active ingredients of polysaccharides before and after digestion.     

Studies on rumen metabolism. VII. Effect of lipids (in vitro) on the digestion of grass fibre and cellulose

Production of propionate from grass fibre, by rumen micro-organisms, in closed systems increased and acetate decreased over 48–72 h incubation periods when lipid was added. Similar effects of lipid on [¹⁴C] propionate and [¹⁴] Cacetate production were obtained when [¹⁴C] cellulose was added to the substrate as a marker. Total volatile fatty acid (VFA) or total [¹⁴C] VFA production from grass fibre was not affected significantly by lipid. Cod liver oil was more effective than either linseed oil or peanut oil in producing these effects. Glycerol liberated from lipid by lipolytic activity would seem to favour acetate formation, rather than propionate formation. When grass fibre was fermented in an artificial micro-rumen for 24 h, addition of oil stimulated the production of total VFA's largely due to significant increases in acetate. Relative rates of formation of the individual short chain fatty acids did not change over a 24 h period. On the other hand, less total [¹⁴C] VFA was produced from [¹⁴C] cellulose in the dialysate of the artificial micro-rumen when oil was added. The specific activities of the individual VFA's were higher without oil but maximum specific activities were obtained slightly earlier when oil was added.     

Effect of rumen ammonia concentration on in situ rate and extent of digestion of feedstuffs

Three dry Holstein cows fitted with rumen fistula were fed a 7.4% crude protein diet consisting of 47.4% corn, 50% cottonseed hulls, and 2.6% minerals and vitamins during a 44-d experiment. Treatments consisted of rumen infusion, 0, 33, 67, and 100 g/d of urea nitrogen applied in a four period Youden Square design. Increasing urea infusion increased rumen fluid ammonia nitrogen from 4.3 to 25.0 mg/dl. Estimated effective dry matter degradation based on in situ rates of digestion were increased from 67.9 to 74.4% for corn and 77.5 to 80.3% for soybean meal with maximums at 100 g/d infused urea nitrogen. Up to 67 g/d infused nitrogen increased dry matter degradation of corn gluten feed from 67.0 to 71.4% and cottonseed meal dry matter degradation from 56.7 to 60.1%. Alfalfa hay dry matter and neutral detergent fiber degradation were not increased by urea infusion. Minimum rumen ammonia required in feeds in this trial were pooled with literature data and suggest that lowest ammonia concentrations required for maximal digestion was a function of the rumen fermentability of the diet or feed. The equation: minimum ammonia concentration (mg/dl) = .452 fermentability % - 15.71, accounted for 50% of the variation in minimum ammonia requirements. We conclude that rumen ammonia concentrations required for maximum digestion are not constant but rather are a function of fermentability of the diet.     

蔗渣Soda-AQ浆二氧化氯脱木素效率研究及纸浆FT-IR分析

研究了蔗渣Soda-AQ浆二氧化氯脱木素(Do)效率的影响因素,得到最佳脱木素工艺条件为ClO2用量0.8%,终点PH值范围为4.0-4.5,反应温度70℃,反应时间60min.在此基础上经D1P和D2P短序ECF漂白后(CLO2用量分别为0.8%和1.0%,H2O2用量2%),蔗渣浆白度分别达到80.2%和81.4%,且具有较好的物理强度.纸浆FT-IR谱图分析表明:蔗渣浆经CLO2脱木素后,纸浆中的羟基和羰基数量增多,愈疮木基和紫丁香基木素单元均受到一定程度的破坏,经H2O2进一步漂白后,木素结构中苯环的特征峰逐渐减弱以至消失,羰基等主要发色基团逐渐减少,纸浆白度得到提高.     

Effect of the combination of monensin and isoacids on rumen fermentation in vitro

Effects of isoacids, monensin, or a combination of them on fermentation by mixed rumen bacteria were investigated using a continuous culture technique. The culture was allowed to stabilize for 4 d before treatments were imposed. Comparisons between treatments were made on d 11 and 12 of the culture. Isoacids (equal proportions of isobutyric, 2-M-butyric, isovaleric, and valeric acids) at 15 mg/dl of culture media increased acetate (6.17 vs. 5.48 meq/dl) and total VFA production (8.93 vs. 7.87 meq/dl) compared with that of controls. Monensin at 150 micrograms/dl reduced acetate (3.74 vs. 6.02 meq/dl) and VFA (6.84 vs. 8.54 meq/dl) but increased propionate (2.28 vs. 1.74 meq/dl) relative to control. The combination of isoacids and monensin increased acetate relative to monensin alone (5.24 vs. 3.74 meq/dl) but did not alter the effect of monensin on propionate concentration (2.32 vs. 2.28 meq/dl). It is concluded that monensin decreases acetate production by 35% and when isoacids are added to the cultures containing monensin, acetate production is restored.     

Effect of pH on cellulose digestion under in vitro conditions

The extent of cellulose digestion by rumen micro-organisms in vitro is dependent on the pH of the medium. Digestion is greatly reduced at pH values similar to those found within the rumen of sheep fed with diets rich in readily digestible carbohydrates. It is suggested that this may be one of the reasons for reduced digestion of the fibre component of forages when carbohydrate supplements are fed.     

NSP酶对大麦体外消化的影响

大麦体外消化试验结果揭示，添加NSP酶（GXC）使大麦中干物质、粗蛋白、粗灰分、无氮浸出物、粗脂肪和粗纤维的消化率分别提高了18．13％、20．27％、15．99％、16．42％、和26．93％和30．02％；大麦中各种氨基酸体外消化率显著提高，幅度为11．83％－61．39％；添加NSP酶使大麦胚乳细胞壁在体外完全降解；消化过滤液中葡萄糖和总氨基酸含量分别提高了17．58％和10．26％；而粘度降低了4．51％。     

The digestion of monosaccharide residues of the cell walls of oat and vetch hays by rumen contents in vitro

The extent and pattern of digestion of oat hay (Avena sativa L.) and vetch hay (Vicia sativa L.) monosaccharides by rumen contents was studied in vitro. The ratios of matrix polysaccharides to lignin were 1.25:1 and 3.82:1 in the vetch and oat hays, respectively. Glucose, xylose and uronic acids were the main sugars in both plants, comprising about 90% of the total monosaccharides. Glucose, xylose and arabinose were mainly confined to the cell walls (CW), whereas galactose and uronic acids were found in high proportions in the soluble fraction. Vetch had a particularly high uronic acid content (14.4 g 100 g^?1 DM), of which 71% was pectic material. The ratios of CW-glucose to CW-xylose were 2.23:1 and 3.74:1 in the oat CW and vetch CW, respectively. Based on monosaccharide analyses of the CW material, it is suggested that the degree of branching of the matrix polysaccharides is about twice as high in vetch as in oat hay. Total glucose and xylose were more digestible in oat than in vetch hay, whereas most of the minor sugars and the total uronic acids were more digestible in the vetch. Irrespective of species, CW glucose was more digestible than CW xylose. The digestibilities of CW glucose, CW xylose and CW uronic acid were: 61.0, 55.3, 51.5, 34.3 and 62.7, 42.6 for the oat hay and vetch hay, respectively. Following the pattern of digestion, CW arabinose and CW glucose were digested faster than CW xylose and CW uronic acid, irrespective of plant species. The extent of digestion at 12 h of incubation of these sugars was higher in vetch than in oat hay. It is suggeted that the concentration ratio of rapidly to slowly degradable CW sugars, in a given plant, is a major determinant of the rate of CW digestion by rumen microorganisms.     

Effect of supplemental yeast culture and dietary starch content on rumen fermentation and digestion in dairy cows

The objectives of this experiment were to evaluate the effect of feeding a culture of Saccharomyces cerevisiae on rumen metabolism and digestibility when cows are fed diets varying in starch content. Four lactating Holstein cows were assigned to a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Treatments were low starch (LS; 23% of diet DM) and no yeast culture (YC; LS-control), LS and 15 g of YC/d (LS-YC), high starch (HS; 29% of diet DM) and no YC (HS-control), and HS and 15 g of YC/d (HS-YC). Periods lasted 28 d, with the last 9 d for data collection. Days 20 to 24 were used to determine production, nutrient flow, and digestibility. On d 25, 3 kg of corn grain DM was placed in the rumen 1 h before the morning feeding, and yields of milk and milk components were measured after the challenge. Blood was sampled −1, 3, 7, and 11 h relative to the morning feeding on d 24 and 25. Rumen pH was measured continuously on d 24 and 25. Rumen papillae were collected on d 24 and 28 to quantify mRNA expression of select genes. Supplementing YC increased yields of milk (26.3 vs. 29.6 kg/d), energy-corrected milk (ECM; 26.5 vs. 30.3 kg/d), fat (0.94 vs. 1.08 kg/d), true protein (0.84 vs. 0.96 kg/d), and ECM/dry matter intake (1.15 vs. 1.30) compared with the control but did not affect dry matter intake (22.6 vs. 22.9 kg/d). Cows fed HS had increased milk true protein percentage (3.18 vs. 3.31%) and yield (0.87 vs. 0.94 kg/d) compared with cows fed LS. Feeding HS-YC increased the proportion of dietary N incorporated into milk true protein from 24.9% in the other 3 treatments to 29.6%. Feeding HS increased the concentration of propionate (21.7 vs. 32.3 mM) and reduced that of NH₃-N (8.3 vs. 6.7 mg/dL) in rumen fluid compared with the control, and combining HS with YC in HS-YC tended to increase microbial N synthesis compared with LS-YC (275 vs. 322 g/d). Supplementing YC to cows fed HS reduced plasma haptoglobin and rumen lactate concentrations, increased mean rumen pH, reduced the time with pH <6.0, and prevented the decrease in rumen neutral detergent fiber digestion caused by HS. Cows fed HS had less total-tract digestion of organic matter (73.9 vs. 72.4%) because of reduced acid detergent fiber (57.6 vs. 51.7%) and neutral detergent fiber (60.9 vs. 56.7%) digestibility. Production performance after the challenge was similar to that before the challenge, and YC improved yield of ECM. After the challenge, supplementing YC tended to reduce rumen lactate concentration compared with the control and reduced haptoglobin in cows fed HS. Feeding HS but not YC increased expression in rumen papillae of genes for receptors (FFAR2 and FFAR3) and transporter (SLC16A3) of short-chain fatty acids but did not affect genes involved in transport of Na⁺/H⁺ or water or in inflammatory response. Supplementing YC to dairy cows improved lactation performance in diets containing low or high starch, and mechanisms might be partially attributed to improvements in rumen pH, digestion of fiber, microbial N synthesis, and reduction in acute phase response.     

Effect of source and amount of fiber on kinetics of digestion and specific gravity of forage particles in the rumen.

This experiment investigated the relationship between kinetics of digestion and change in specific gravity during in situ incubation. Nine cows were fed three sources of fiber (corn silage, alfalfa silage, or alfalfa hay) in diets formulated to contain 25, 30, or 35% NDF in three simultaneous 3 x 3 Latin squares. Method of alfalfa preservation did not influence rate of digestion or rate of increase in specific gravity of forage particles measured by a flotation technique. Prior to incubation, specific gravity of forage particles was in increasing order: alfalfa hay, alfalfa silage, and then corn silage. Essentially, all particles with a specific gravity less than 1.0 shifted to a higher specific gravity fraction by hydration within the first 4 h of incubation. From 4 to 56 h of incubation, percentage of residual DM that settled in solution having specific gravity of 1.3 increased linearly from 21 to 27% for corn silage but exponentially from 3 to 20% for alfalfa forages. Fractional rates of DM and NDF digestion and increase in percentage of residual DM having a specific gravity greater than 1.3 increased with the amount of fiber in the alfalfa diets and were correlated positively, suggesting that rate of increase in specific gravity, which affects rate of passage from the rumen, is influenced by rate of digestion of forage particles.     

抗性淀粉体外消化模拟的研究

采用体外消化模拟方法,研究了抗性淀粉在人工胃肠液和大肠液中的消化吸收情况,并用原淀粉作为对照组。结果表明,抗性淀粉和原淀粉在生理盐水中均没有被分解,生理盐水对抗性淀粉的消化毫无影响。与对照组原淀粉相比,抗性淀粉在人工胃液(pH3、pH4、pH5)和人工肠液(pH6.8)中变化很小,人工胃液和人工肠液对抗性淀粉不起消化作用。抗性淀粉在大肠液中有明显的失重,说明大肠液对抗性淀粉有影响,抗性淀粉能够被大肠中的微生物发酵或部分发酵。从而说明抗性淀粉不能在胃和小肠中消化吸收。     

复合生物酶处理对苘麻木质素去除的影响

以脱胶煮炼酶CKD(R)为代表的复合生物酶开始被广泛用于苎麻脱胶中,亚麻、黄麻等木质素含量相对高的麻纤维能否采用CKD(R)进行脱胶,木质素去除效果是关键.针对这一问题,文章探讨了脱胶煮炼酶CKD(R)在处理木质素含量相对高的苘麻纤维时木质素的去除情况.实验结果表明,CKD(R)酶对苘麻木质素有一定去除作用,去除率为11.60%;实验还获得了CKD(R)酶处理苘麻的最佳工艺,影响木质素去除的主次要排列次序依次为:处理温度、CKD(R)酶浓度、处理时间;CKD(R)酶处理过程中,木质素的去除率受温度、时间、酶用量3个因素的协同作用.     

Effect of bovine somatotropin and protein on rumen fermentation and forestomach and whole tract digestion in dairy cows.

Four lactating Holstein cows with permanent ruminal and duodenal cannulas were allocated to one of two TMR with either 17.1 or 23.6% CP at 5 to 9 d postpartum. Cows also were assigned to either bST (20.6 mg/d) or excipient (control) treatment at that time for the 84-d experiment but were switched to different protein levels every 21 d in four periods. Intake of DM and forestomach and whole tract digestion of DM were unaffected by treatments. Forestomach and whole tract apparent digestion of N was higher for cows fed the high protein diet. Forestomach NDF and ADF digestion was higher for cows fed the high protein diet but was significant for control cows only. Rumen pH, ammonia N, and isovalerate were higher for cows fed the high protein diet. Rumen ammonia N and acetate were lower for bST-treated cows. Rumen pool sizes of total ingesta, DM, NDF, and bacterial OM were not affected by either treatment. However, the total pool size of rumen NAN and nonbacterial NAN was larger for cows fed the high protein diet. Duodenal flow of AA was higher for cows fed the high protein diet. However, duodenal protein AA profiles were similar among treatments except for lysine, which was higher, and methionine and alanine, which tended to be lower, for cows fed the high protein diet. There were few bST x protein or bST x duration of treatment interactions. Results support the concept that bST-treated cows have digestive metabolism similar to untreated cows of similar actual production.     

Role of polysaccharides in food,digestion, and health

Polysaccharides derived from plant foods are major components of the human diet, with limited contributions of related components from fungal and algal sources. In particular, starch and other storage carbohydrates are the major sources of energy in all diets, while cell wall polysaccharides are the major components of dietary fiber. We review the role of these components in the human diet, including their structure and distribution, their modification during food processing and effects on functional properties, their behavior in the gastrointestinal tract, and their contribution to healthy diets.     

菊糖对马铃薯淀粉糊流变特性及体外消化的影响

为了研究菊糖对马铃薯淀粉糊流变特性及体外消化的影响,以马铃薯淀粉为原料,通过流变仪测试和体外酶解等方法测定菊糖-马铃薯淀粉共混体系的特性变化。流变仪测试结果表明:在试验的菊糖添加量范围内,菊糖-马铃薯淀粉共混糊的流变学特性均符合幂率模型,为假塑性流体;菊糖的添加在一定程度上降低了淀粉糊黏度,且随着添加量的增加,这一趋势加大。体外酶解结果表明:菊糖可以在一定程度上抑制马铃薯淀粉的水解速度及程度,且随着菊糖添加量的增加其抑制程度也相应增加;水解指数HI及预测血糖值e GI均随着菊糖添加量的增加而逐渐降低;在菊糖最大添加量时(菊糖与淀粉配比为1∶5),菊糖-淀粉共混体系的水解率、HI和e GI值分别由原淀粉的70%、57.87和71.48降至50%、42.74和63.17。研究结果提示适量的菊糖不仅可以改善马铃薯淀粉糊的流变性能,还可以降低其血糖指数。     

Effect of ratio of roughage concentrate on glucose-induced heat production in sheep rumen fluid in vitro

The effect of ration on heat of glucose fermentation in sheep rumen fluid was investigated. Heat production was measured in a semiadiabatic calorimeter. In trial 1, the effect of glucose (.4 to 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25 or 100% roughage diet. Heat of glucose fermentation decreased with increase in glucose dose in both diets. Maximal heat of glucose fermentation in both diets agreed with stoichiometric calculations. However, at 6.4 mg glucose, maximal heat was 18 kcal/mol in the 25% roughage diet and 14 kcal/mol in the 100% roughage diet. Purine N and maximal rate of heat production were not affected by diet type. In trial 2, the effect of glucose (1.6 and 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25, 50, 75, and 100% roughage. In addition, fermentation pattern was measured in donors of the rumen fluid. Heat of glucose fermentation was positively correlated with organic matter digestibility and negatively correlated with rumen pH and acetate concentration. These observations indicate that in addition to the effect of roughage on the fermentation pattern, supplemental adaptation may occur, as indicated by the reduction in the heat of glucose fermentation.     

脂肪酸碳链长度对甘三酯体外模拟消化的影响

用pH-stat法模拟不同脂肪酸链长甘三酯的人体体外消化过程,从乳化粒径的角度研究脂肪酸碳链长度对甘三酯体外消化速率的影响。结果表明:三辛酸甘油酯(C8)乳化后,平均粒径最小,其他与之碳数相差越多则粒径越大;整体消化过程中三辛酸甘油酯(C8)的消化速率最高,其他与之碳数相差越多则消化速率越小。乳糜微粒的粒径大小与甘三酯的消化速率呈负相关的关系。消化速率的大小顺序为三辛酸甘油酯(C8)三月桂酸甘油酯(C12)三乙酸甘油酯(C2)三硬脂酸甘油酯(C18)。     

体外模拟消化对酸枣仁蛋白酶解产物抗氧化活性的影响

目的:以具有良好抗氧化活性的酸枣仁蛋白酶解产物(SZPHs)为研究对象,探究体外模拟胃肠消化对其氨基酸组成及抗氧化活性的影响.方法:通过体外模拟胃肠消化,得到酸枣仁蛋白酶解产物消化物(SZPHs-GD),并分析SZPHs消化前后的氨基酸组成以及体外抗氧化活性.结果:体外模拟胃肠消化后,SZPHs-GD中疏水性氨基酸含量...