Dietary tannins and salivary proline-rich proteins: interactions, induction, and defense mechanisms

Relationship between Plasma and Saliva Urea Nitrogen Concentrations in New Zealand Red Deer Calves (Cervus elaphus)

Red deer (Cervus elaphus), like other ruminants, excrete approximately 70% of the nitrogen they ingest. Developing ways in which to reduce the rate of loss, such as manipulating the diet or selecting for efficiency of growth, requires close monitoring of the plasma urea N (PUN) concentration which, in turn, requires a simple, safe, and reliable method for collecting samples. Saliva is easier to collect than blood, but the relationship between the salivary urea N (SUN) and the PUN is not known for red deer. This was therefore evaluated in two strains of mixed-sex red deer calves (Cervus elaphus): a phenotype with a high seasonality of growth (H, n = 10) and a phenotype with a low seasonality of growth (L, n = 13). Both phenotypes were divided into two groups, which were each offered one of two forage-based diets ad libitum: a medium-quality diverse treatment and a low-quality perennial ryegrass-white clover treatment. Blood and saliva samples for the determination of the PUN and SUN were collected at dawn every four weeks for five months (April to September 2022). There was a strong linear relationship between the PUN and SUN in the pooled sample (R2 = 0.65, p < 0.001). The estimations of the PUN were significantly improved by adding diet and the date of sampling into the model (p < 0.001), but not phenotype (p > 0.75). SUN represents a reliable index of the PUN, and collecting saliva therefore represents a simple and inexpensive alternative to collecting blood samples in studies of nitrogen metabolism in red deer.

Effects of the Taste Substances and Metal Cations in Green Tea Infusion on the Turbidity of EGCG-Mucin Mixtures

Astringency has an important impact on the taste quality of tea infusion, a process which occurs when polyphenols complex with salivary proteins to form an impermeable membrane. (-)-Epigallocatechin gallate (EGCG) is the main astringent compound found in green tea and mucin is the main protein present in saliva. Determining the turbidity of EGCG-mucin mixtures is an effective method to quantify the astringency intensity of EGCG solutions. In this study, the effects of taste-related, substances present during green tea infusion, on the turbidity of EGCG-mucin mixtures was investigated under the reacting conditions of a pH value of 5.0, at 37 °C, and for 30 min. The results showed that epicatechins, caffeic acid, chlorogenic acid, and gallic acid reduced the turbidity of EGCG-mucin mixtures, while rutin increased turbidity. Metal ions increased the turbidity of EGCG-mucin mixtures. These can be arranged by effectiveness as Al3+ > K+ > Mg2+ > Ca2+. Caffeine, theanine, and sodium glutamate all decreased the turbidity values of EGCG-mucin mixtures, but sucrose had a weak effect. Further experiments confirmed that the turbidity of green tea infusion-mucin mixture indicated the astringent intensity of green tea infusion, and that the turbidity was significantly correlated with the contents of tea polyphenols and EGCG.

Comparison of Black Tea Waste and Legume Roughages: Methane Mitigation and Rumen Fermentation Parameters

The chemical composition, in vitro total gas and CH₄ production and performance of cattle fed on factory black tea waste (Camellia sinensis) (BTW), alfalfa (Medicago Sativa), sainfoin (Onobrychis sativa) and white clover (Trifolium repens) was investigated. The gas production was quantified at the 24th hour of the incubation process. BTW was found to vary from roughages in chemical composition (p < 0.05). In addition, the roughages differed in terms of nutrient composition and gas production (p < 0.05). In legume roughages, acetic acid (AA), propionic acid (PA), butyric acid (BA), and total volatile fatty acids (TVFA) values ranged from 52.36-57.00 mmol/L, 13.46-17.20 mmol/L, 9.79-12.43 mmol/L, and 79.71-89.05 mmol/L, respectively. In comparison with black tea waste, legume roughages had higher values of AA, PA, BA, and TVFA. Black tea waste contained a higher acetic acid ratio than legume roughages when compared as a percentage. There was a similar ratio of propionic acid to the rate calculated for sainfoin (Onobrychis sativa) and clover (Trifolium repens), and a similar ratio of butyric acid to the ratio determined for alfalfa (Medicago Sativa). The current study shows that the 5.7-6.3% tannin content of black tea waste can be used in ruminant rations with high-quality roughages. Due to the fact that BTW reduces methane emissions from ruminants and eliminates energy waste from them, the environment can be improved. To obtain more reliable results, further animal feeding experiments on legume roughages and BTW are required.

The role of saliva in taste and food intake

Saliva is well-described in oral food processing, but its role in taste responsiveness remains understudied. Taste stimuli must dissolve in saliva to reach their receptor targets. This allows the constituents of saliva the opportunity to interact with taste stimuli and their receptors at the most fundamental level. Yet, despite years of correlational data suggesting a role for salivary proteins in food preference, there were few experimental models to test the role of salivary proteins in taste-driven behaviors. Here we review our experimental contributions to the hypothesis that salivary proteins can alter taste function. We have developed a rodent model to test how diet alters salivary protein expression, and how salivary proteins alter diet acceptance and taste. We have found that salivary protein expression is modified by diet, and these diet-induced proteins can, in turn, increase the acceptance of a bitter diet. The change in acceptance is in part mediated by a change in taste signaling. Critically, we have documented increased detection threshold, decreased taste nerve signaling, and decreased oromotor responding to quinine when animals have increases in a subset of salivary proteins compared to control conditions.

Traces of dietary patterns in saliva of hominids: Profiling salivary amino acid fingerprints in great apes and humans

Herbivorous animals that regularly consume tannin-rich food are known to secrete certain tannin-binding salivary proteins (TBSPs), especially proline-rich proteins and histidine-rich proteins, as an effective measure to counteract the antinutritive effects of dietary tannins. Due to their high binding capacity, TBSPs complex with tannins in the oral cavity, and thereby protect dietary proteins and digestive enzymes. Although the natural diet of great apes (Hominidae) is biased toward ripe fruits, analyses of food plants revealed that their natural diet contains considerable amounts of tannins, which is raising the question of possible counter-measures to cope with dietary tannins. In our study, we investigated the salivary amino acid profiles of zoo-housed Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo abelii, and compared their results with corresponding data from Homo sapiens. Individual saliva samples of 42 apes and 17 humans were collected and quantitated by amino acid analysis, using cation-exchange chromatography with postcolumn derivatization, following acid hydrolysis. We found species-specific differences in the salivary amino acid profiles with average total salivary protein concentration ranging from 308.8 mg/dL in Po. abelii to 1165.6 mg/dL in G. gorilla. Total salivary protein was consistently higher in ape than in human saliva samples (174 mg/dL). All apes had on average also higher relative proline levels than humans did. Histidine levels had the highest concentration in the samples from Po. abelii followed by P. paniscus. In all ape species, the high salivary concentrations of proline and histidine are considered to be indicative of high concentrations of TBSPs in hominids. Given that the species differences in salivary composition obtained in this study correspond with overall patterns of secondary compound content in the diet of wild populations, we assume that salivary composition is resilient to acute and long-lasting changes in diet composition in general and tannin content in particular.

Removal of astringency from persimmon paste via polysaccharide treatment

Non-astringent persimmon (Diospyros kaki Thunb.) paste is typically produced by treating astringent persimmon fruit with alcohol or dry ice (to remove tannins) followed by abrasion. However, considering the large yield of astringent persimmons harvested in a short time, this long, laborious method has hindered the use of persimmon paste in food processing. Herein, the addition of polysaccharides was used to produce a non-astringent persimmon paste while maintaining its quality. Among the nine evaluated polysaccharides, high- (HM) and low-methoxyl (LM) pectins, carrageenan, xanthan gum, and sodium alginate exhibited high astringency removal efficiencies. No astringency recurrence was observed after freezing when HM or LM pectin, guar gum, carrageenan, or sodium alginate were added. Moreover, the addition of HM pectin, or LM pectin, or sodium alginate prevented astringency upon heating. Additionally, guar, xanthan, tara gum, or carrageenan effectively inhibited syneresis. Thus, high-quality pastes could be easily and efficiently produced using a combination of polysaccharides.

Salivary Gland Adaptation to Dietary Inclusion of Hydrolysable Tannins in Boars

Simple Summary

Tannins have traditionally been avoided in animal nutrition due to their anti-nutritive effects. However, recent studies reported hydrolysable tannins as beneficial additives that have antimutagenic, anticarcinogenic, antidiarrheal, and antiulcerogenic effects on animals. In a study testing the inclusion of hydrolysable tannins as a potential nutritive factor to reduce boar taint in entire males, significant enlargement of the parotid glands (parotidomegaly) was observed. In this study, we aimed to determine the morphological and immunohistochemical basis for the observed parotidomegaly. We discovered that enlargement of glandular lobules and acinar area, an increased ratio between the nucleus and cytoplasm of serous cells, and increased excretion of proline-rich proteins (PRPs) were characteristic of the experimental group that received the highest dietary tannin intake. The mandibular salivary gland, on the other hand, did not show significant morphological changes among the experimental groups. This suggests increased functional activity of the parotid salivary glands as the first and most important line of defense against high dietary tannin and its potential negative effects.

Abstract

The ingestion of hydrolysable tannins as a potential nutrient to reduce boar odor in entire males results in the significant enlargement of parotid glands (parotidomegaly). The objective of this study was to characterize the effects of different levels of hydrolysable tannins in the diet of fattening boars (n = 24) on salivary gland morphology and proline-rich protein (PRP) expression at the histological level. Four treatment groups of pigs (n = 6 per group) were fed either a control (T0) or experimental diet, where the T0 diet was supplemented with 1% (T1), 2% (T2), or 3% (T3) of the hydrolysable tannin-rich extract Farmatan^®. After slaughter, the parotid and mandibular glands of the experimental pigs were harvested and dissected for staining using Goldner’s Trichrome method, and immunohistochemical studies with antibodies against PRPs. Morphometric analysis was performed on microtome sections of both salivary glands, to measure the acinar area, the lobular area, the area of the secretory ductal cells, and the sizes of glandular cells and their nuclei. Histological assessment revealed that significant parotidomegaly was only present in the T3 group, based on the presence of larger glandular lobules, acinar areas, and their higher nucleus to cytoplasm ratio. The immunohistochemical method, supported by color intensity measurements, indicated significant increases in basic PRPs (PRB2) in the T3 and acidic PRPs (PRH1/2) in the T1 groups. Tannin supplementation did not affect the histo-morphological properties of the mandibular gland. This study confirms that pigs can adapt to a tannin-rich diet by making structural changes in their parotid salivary gland, indicating its higher functional activity.

Stable isotopes provide evidence that condensed tannins from sericea lespedeza are degraded by ruminal microbes

The objective of Trial 1 was to determine the effects of condensed tannins (CT) from sericea lespedeza [SL; Lespedeza cuneata (Dum. Cours.) G. Don] on in vitro digestible organic matter (IVDOM), total gas production (GP), methane (CH₄) emission, and ruminal fluid parameters after fermentation. Substrates used in four 48-h in vitro fermentations were 100% bermudagrass [(Cynodon dactylon (L.) Pers.] hay (0SL), 100% SL hay (100SL), and a mix of both hays (50SL). Linear reductions were observed for all parameters (P < 0.05) with the inclusion of SL, except for CH₄ in relation to GP, that presented a quadratic effect (P = 0.005). In Trial 2, SL plants were enriched with ¹³C-CO₂ to obtain pure enriched CT to identify the destination of fermentation end products of CT degradation. The enrichment of CT through the SL was successful (P < 0.001), and carbon originated from CT was detected in the fermentation end products [microbial mass, clarified rumen fluid, and in the CH₄ produced (P < 0.001)]. Therefore, inclusion of SL was effective in reducing in vitro CH₄ production and compound-specific tracing of δ¹³C abundance provided better quantitative understanding of the mechanisms of partitioning CT during ruminal fermentation processes.

Nutritional challenges of feeding a mutualist: Testing for a nutrient-toxin tradeoff in fungus-farming leafcutter ants

The biochemical heterogeneity of food items often yields tradeoffs as each bite of food tends to contain some nutrients in surplus and others in deficit, as well as other less palatable or even toxic compounds. These multidimensional nutritional challenges are likely compounded when foraged foods are used to provision others (e.g. offspring or symbionts) with different physiological needs and tolerances. We explored these challenges in free-ranging colonies of leafcutter ants that navigate a diverse tropical forest to collect plant fragments they use to provision a co-evolved fungal cultivar. We tested the prediction that leafcutter farmers face provisioning tradeoffs between the nutritional quality and concentration of toxic tannins in foraged plant fragments. Chemical analyses of plant fragments sampled from the mandibles of Panamanian Atta colombica leafcutter ants provided little support for a nutrient-tannin foraging tradeoff. First, colonies foraged for plant fragments ranging widely in tannin concentration. Second, high tannin levels did not appear to restrict colonies from selecting plant fragments with blends of protein and carbohydrates that maximized cultivar performance when measured with in vitro experiments. We also tested whether tannins expand the realized nutritional niche selected by leafcutter ants into high-protein dimensions since: 1) tannins can bind proteins and reduce their accessibility during digestion, and 2) in vitro experiments have shown that excess protein provisioning reduces cultivar performance. Contrary to this hypothesis, the most protein-rich plant fragments did not have highest tannin levels. More generally, the approach developed here can be used to test how multidimensional interactions between nutrients and toxins shape the costs and benefits of providing care to offspring or symbionts.

Biomedical applications of tannic acid

Tannic Acid (TA) is a naturally occurring antioxidant polyphenol that has gained popularity over the past decade in the field of biomedical research for its unique biochemical properties. Tannic acid, typically extracted from oak tree galls, has been used in many important historical applications. TA is a key component in vegetable tanning of leather, iron gall ink, red wines, and as a traditional medicine to treat a variety of maladies. The basis of TA utility is derived from its many hydroxyl groups and its affinity for forming hydrogen bonds with proteins and other biomolecules. Today, the study of TA has led to the development of many new pharmaceutical and biomedical applications. TA has been shown to reduce inflammation as an antioxidant, act as an antibiotic in common pathogenic bacterium, and induce apoptosis in several cancer types. TA has also displayed antiviral and antifungal activity. At certain concentrations, TA can be used to treat gastrointestinal disorders such as hemorrhoids and diarrhea, severe burns, and protect against neurodegenerative diseases. TA has also been utilized in biomaterials research as a natural crosslinking agent to improve mechanical properties of natural and synthetic hydrogels and polymers, while also imparting anti-inflammatory, antibacterial, and anticancer activity to the materials. TA has also been used to develop thin film coatings and nanoparticles for drug delivery. In all, TA is fascinating molecule with a wide variety of potential uses in pharmaceuticals, biomaterials applications, and drug delivery strategies.

Effect of Scomberomorus niphonius peptide on the characteristics of resveratrol

Resveratrol has a variety of physiological activities, but its bioavailability in the body is low. In this study, the interaction between the peptide SH, prepared from Scomberomorus niphonius, and resveratrol was judged by fluorescence spectroscopy. Then, SHa1 was obtained by the purification of SH, and its effect on the characteristics of resveratrol was studied. SHa1 interacted with resveratrol at 37 °C for 30 min to obtain the complex SHa1-R, which then showed an obviously stronger inhibition on B16 cells than resveratrol using the MTT assay after in vitro gastrointestinal digestion. The solubility and digestive stability of SHa1-R were higher than that of free resveratrol. The intestinal absorption rate of SHa1-R was also increased compared with resveratrol according to the non-inverted rat intestinal sac model. The structure of SHa1 was analyzed by UPLC, auto amino acid analysis, and UPLC-MS/MS. The molecular weight of SHa1 was mainly concentrated under 1000 Da, and it was rich in glutamic acid, aspartic acid, lysine, and leucine. Eighteen possible peptides were identified from SHa1. The results suggested that the peptide SHa-1 may help to increase the bioavailability of resveratrol by increasing the solubility, digestive stability and intestinal absorption of resveratrol, thereby promoting its inhibitory effect on B16 cells.

Ellagitannin Digestion in Moth Larvae and a New Dimeric Ellagitannin from the Leaves of Platycarya strobilacea

Ellagitannins (ETs) are plant polyphenols with various health benefits. Recent studies have indicated that the biological activities of ETs are attributable to their degradation products, including ellagic acid and its gut microflora metabolites, such as urolithins. Insect tea produced in the Guangxi region, China, is made from the frass of moth larvae that feed on the ET-rich leaves of Platycarya strobilacea. Chromatographic separation of the Guangxi insect tea showed that the major phenolic constituents are ellagic acid, brevifolin carboxylic acid, gallic acid, brevifolin, and polymeric polyphenols. Chemical investigation of the feed of the larvae, the fresh leaves of P. strobilacea, showed that the major polyphenols are ETs including pedunculagin, casuarictin, strictinin, and a new ET named platycaryanin E. The new ET was confirmed as a dimer of strictinin having a tergalloyl group. The insect tea and the leaves of P. strobilacea contained polymeric polyphenols, both of which were shown to be composed of ETs and proanthocyanidins by acid hydrolysis and thiol degradation. This study clarified that Guangxi insect tea contains ET metabolites produced in the digestive tract of moth larvae, and the metabolites probably have higher bioavailabilities than the original large-molecular ETs of the leaves of P. strobilacea.

Dietary choices in a generalist herbivore, the eastern cottontail Sylvilagus floridanus, in urban landscapes

We tested for dietary choices of foods varying in nutrient composition by cottontail rabbits on two college campuses in midwestern USA. We quantified choices among pellets of varying nutritional quality at artificial food patches. Dietary choices differed between seasons and locations. Spring giving-up densities (GUDs: food left behind) did not show differences in food choices and were lower than summer GUDs. In Appleton, the cottontails favoured both high protein and fibre pellets, whereas the medium protein and fibre pellets were favoured in Chicago. The cottontails maintained their choice of high protein, high fibre pellets at three spatial scales. The cottontails varied food intake to balance their protein, salt and fibre needs at different times and locations. Studying dietary choices and the effect of resource quality on foraging responses by urban wildlife provides a useful tool to study ecological interactions and can help minimize damage in urban environments such as parks.

Condensed tannins in the diet of folivorous diademed sifakas and the gap between crude and available protein

Tannins, a type of plant secondary metabolite, are well-known for their ability to precipitate proteins and thereby reduce the protein available to consumers. Most primate studies have focused on condensed tannins (CTs) as they were thought to be the most effective type of tannin at preventing protein acquisition, but there is growing recognition that other types of tannins can bind to proteins, suggesting the division among tannin types is not as clear-cut as previously thought. Although previous studies have documented the presence of CTs in primate diets and primates' behavioral responses to them, our understanding of tannins remains limited because few researchers have used Sephadex column purification to accurately determine tannin concentrations, and few have used in vitro assays to determine available protein content and the tannins' effectiveness in binding protein. In this study, we documented diademed sifaka (Propithecus diadema) diet from June to August 2018 at Tsinjoarivo, Madagascar (in two forests with varying degrees of habitat disturbance) and quantified CT concentration and actual available protein in foods. Eleven of the fourteen top foods tested contained CTs (concentrations: 4.8%-39.3% dry matter). An in vitro assay showed available protein was strikingly low in six of the eleven top foods (e.g., little to no apparent available protein, despite high crude protein). Overall, our findings suggest sifakas acquire less protein than previously recognized and probably have adaptations to counteract tannins. Such studies of available protein are critical in understanding dietary constraints on sifaka populations and the evolution of their diet choice strategies; despite the conventional wisdom that leaves are protein-rich, folivorous primates may indeed be protein-limited. However, further studies are necessary to determine if sifakas have counter-adaptations to tannins, and if they absorb more protein than our analyses suggest, perhaps receiving protein that we were unable to detect with the current techniques (e.g., pollen).

Reproductive responses of the male Brandt’s vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid

Tannins are polyphenols that are present in various plants, and potentially contain antioxidant properties that promote reproduction in animals. This study investigated how tannic acid (TA) affects the reproductive parameters of male Brandt’s voles,Lasiopodomys brandtii(Radde, 1861). Specifically, the anti-oxidative level of serum, autophagy in the testis, and reproductive physiology were assessed in males treated with TA from the pubertal stage. Compared to the control, low dose TA enhanced relative testis and epididymis weight and sperm concentration in the epididymis, and significantly increased the level of serum superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). mRNA levels of autophagy related genes LC3 and Beclin1 decreased significantly with low dose TA compared to the control. However, compared to the control, high dose TA sharply reduced the levels of serum SOD, GSH-Px, CAT, serum testosterone (T), and mRNA level in steroidogenic acute regulatory protein (StAR) in the testis. Both sperm abnormality and mortality increased with high dose TA compared to the control and low dose TA. Collectively, this study demonstrated that TA treatment during puberty had a dose-dependent effect on the reproductive responses of male Brandt’s voles. TA might mediate autophagy in the testis, through both indirect and direct processes. TA mainly affected the reproductive function of male Brandt’s voles by regulating anti-oxidative levels. This study advances our understanding of the mechanisms by which tannins influence reproduction in herbivores.

Are there phylogenetic differences in salivary tannin-binding proteins between browsers and grazers, and ruminants and hindgut fermenters?

While feeding, mammalian browsers (primarily eat woody plants) encounter secondary metabolites such as tannins. Browsers may bind these tannins using salivary proteins, whereas mammalian grazers (primarily eat grasses that generally lack tannins) likely would not. Ruminant browsers rechew their food (ruminate) to increase the effectiveness of digestion, which may make them more effective at binding tannins than nonruminants. Few studies have included a sufficient number of species to consider possible scaling with body mass or phylogenetic effects on salivary proteins. Controlling for phylogeny, we ran inhibition radial diffusion assays of the saliva of 28 species of African herbivores that varied in size, feeding strategy, and digestive system. We could not detect the presence of salivary proline-rich proteins that bind tannins in any of these species. However, using the inhibition radial diffusion assay, we found considerable abilities to cope with tannins in all species, albeit to varying degrees. We found no differences between browsers and grazers in the effectiveness of their salivary proteins to bind to and precipitate tannins, nor between ruminants and nonruminants, or scaling with body mass. Three species bound all tannins, but their feeding niches included one browser (gray duiker), one mixed feeder (bush pig), and one grazer (red hartebeest). Five closely related species of small ruminant browsers were very effective in binding tannins. Megaherbivores, considered generalists on account of their large body size, were capable of binding tannins. However, the grazing white rhinoceros was almost as effective at binding tannins as the megaherbivore browsers. We conclude, contrary to earlier predictions, that there were no differences in the relative salivary tannin-binding capability that was related to common ancestry (phylogeny) or to differences in body size.

Response of Fattening Rabbits with Acorns (Quercus pubescens Willd.) Combined in the Diet: First Acquaintances on Growth Performance, Carcass Traits and Perirenal Fatty Acid Profile

The request for functional and healthy meat presents a challenge to modern animal nutritionists and rabbit meat consumption appears to increase alongside the aging population. Novel functional feeds for food-producing animals gather the interest of the scientific community and acorns appear frequently accounted among non-competitive-with-human feeding sources, above all in slow food production systems. This investigation aimed to assess the response to acorns combined in the diet of 40 fattening rabbits, in respect of growth performance, carcass characteristics and fatty acids composition in perirenal fat. A same commercial fattening diet combined or not with shredded acorns (control, CON = 0 vs. acorn combined diet, ACD = 200 g/kg feed as fed weight, respectively) was administered for six weeks to two groups of Separator rabbits, consisting of 20 animals each. No differences in feed conversion, carcass weight at slaughter and carcass yields (24 h) were found between groups at the end of the experimental feeding. Perirenal fat profile of rabbits from the ACD group pointed to significant differences in ΣPUFA content (25.1 vs. 31.6, as a percentage of total lipids, respectively, p < 0.001) and in the Σ n - 6/n - 3 ratio (5.95 vs. 2.41). In conclusion, acorns can be used as an energy source in mixed feeds for rabbits, especially in slow production systems.

Tannins in Food: Insights into the Molecular Perception of Astringency and Bitter Taste

Astringency and bitterness are organoleptic properties widely linked to tannin compounds. Due to their significance to food chemistry, the food industry, and to human nutrition and health, these tannins' taste properties have been a line of worldwide research. In recent years, significant advances have been made in understanding the molecular perception of astringency pointing to the contribution of different oral key players. Regarding bitterness, several polyphenols have been identified has new agonists of these receptors. This review summarizes the last data about the knowledge of these taste properties perceived by tannins. Ultimately, tannins' astringency and bitterness are hand-in-hand taste properties, and future studies should be adapted to understand how the proper perception of one taste could affect the perception of the other one.

Development of a New Cell-Based Oral Model To Study the Interaction of Oral Constituents with Food Polyphenols

Some polyphenols have unpleasant taste properties such as astringency, which could interfere with consumers' choices. The knowledge on astringency mechanisms points that astringency is a complex phenomenon probably related to more than one physical-chemical mechanism. Thus, this work aims to develop a new and more realistic cell-based model containing human saliva, mucosa pellicle, and an oral cell line (HSC-3) to understand the oral molecular events that could contribute to the overall astringency perception. This model was then used to study the interactions with a food procyanidin fraction (PF) by HPLC. In general, the results revealed higher interaction (synergism) for the model with all the referred oral constituents (mucosa pellicle, salivary proteins, and HSC-3 cell line, HSCMuSp) when compared to the interaction with individual constituents, the PF + cells or PF + saliva. Regarding the procyanidins, a significant interaction was observed for the procyanidin monomer EcG, procyanidin dimers B7 and B2G, and trimer C1.

Bitter-Induced Salivary Proteins Increase Detection Threshold of Quinine, But Not Sucrose

Exposures to dietary tannic acid (TA, 3%) and quinine (0.375%) upregulate partially overlapping sets of salivary proteins which are concurrent with changes in taste-driven behaviors, such as rate of feeding and brief access licking to quinine. In addition, the presence of salivary proteins reduces chorda tympani responding to quinine. Together these data suggest that salivary proteins play a role in bitter taste. We hypothesized that salivary proteins altered orosensory feedback to bitter by decreasing sensitivity to the stimulus. To that end, we used diet exposure to alter salivary proteins, then assessed an animal's ability to detect quinine, using a 2-response operant task. Rats were asked to discriminate descending concentrations of quinine from water in a modified forced-choice paradigm, before and after exposure to diets that alter salivary protein expression in a similar way (0.375% quinine or 3% TA), or 1 of 2 control diets. Control animals received either a bitter diet that does not upregulate salivary proteins (4% sucrose octaacetate), or a nonbitter diet. The rats exposed to salivary protein-inducing diets significantly decreased their performance (had higher detection thresholds) after diet exposure, whereas rats in the control conditions did not alter performance after diet exposure. A fifth group of animals were trained to detect sucrose before and after they were maintained on the 3% TA diet. There was no significant difference in performance, suggesting that these shifts in threshold are stimulus specific rather than task specific. Taken together, these results suggest that salivary proteins reduce sensitivity to quinine.

Treatments and uses of Moringa oleifera seeds in human nutrition: A review

This work reviews treatments and uses of Moringa oleifera seeds in human nutrition. Moringa oleifera seeds are considerable sources of proteins (mean 19%) and lipids (mean 31%). Previous reports presented the nutritional properties of the seeds and oil. Moringa seeds are sources of lipids, and their removal leads to Moringa seed flour with a high protein content which might play a role in food technology and human nutrition. Moringa oil has been tested in frying and was found to be more stable than groundnut oil; its incorporation in groundnut at level lower than 10% improved on the acceptability of chips. Several treatments like roasting, germination, and boiling have been applied to Moringa seeds to produce flour with improved nutritional properties. In particular, defatted Moringa flour has been applied in different formulations including cakes, cookies, burgers, infant porridges. Generally, the products deriving from the flour were more stable in conservation and well accepted for low substitution while high substitution increased the bitterness. Notwithstanding their high content in protein and oil, defatted M. oleifera seed flour and oil are still fairly investigated in order to envisage their integration in the food habits of people. The present wrote up reviews the treatments applied on M. oleifera seeds and applications of the defatted M. oleifera flour and oil in food systems for human nutrition.

Metabolomics reveals diet-derived plant polyphenols accumulate in physiological bone

Plant-derived secondary metabolites consumed in the diet, especially polyphenolic compounds, are known to have a range of positive health effects. They are present in circulation after ingestion and absorption and can be sequestered into cells within particular organs, but have rarely been investigated systematically in osteological tissues. However, a small number of polyphenols and similar molecules are known to bind to bone. For example alizarin, a plant derived anthraquinone and tetracycline (a naturally occurring antibiotic), are both absorbed into bone from circulation during bone formation and are used to monitor mineralization in osteological studies. Both molecules have also been identified serendipitously in archaeological human bones derived from natural sources in the diet. Whether an analogous mechanism of sequestration extends to additional diet-derived plant-polyphenols has not previously been systematically studied. We investigated whether a range of diet-derived polyphenol-like compounds bind to bone using untargeted metabolomics applied to the analysis of bone extracts from pigs fed an acorn-based diet. We analysed the diet which was rich in ellagitannins, extracts from the pig bones and surrounding tissue, post-mortem. We found direct evidence of multiple polyphenolic compounds in these extracts and matched them to the diet. We also showed that these compounds were present in the bone but not surrounding tissues. We also provide data showing that a range of polyphenolic compounds bind to hydroxyapatite in vitro. The evidence for polyphenol sequestration into physiological bone, and the range and specificity of polyphenols in human and animal diets, raises intriguing questions about potential effects on bone formation and bone health. Further studies are needed to determine the stability of the sequestered molecules post-mortem but there is also potential for (palaeo)dietary reconstruction and forensic applications.

Development of a direct ESI-MS method for measuring the tannin precipitation effect of proline-rich peptides and in silico studies on the proline role in tannin-protein interactions

Tannins are a heterogeneous class of polyphenols that are present in several plants and foods. Their ability to interact and precipitate proline-rich proteins leads to different effects such as astringency or antidiarrheal activity. Thus, evaluation of the tannin content in plant extracts plays a key role in understanding their potential use as pharmaceuticals and nutraceuticals. Several methods have been proposed to study tannin-protein interactions but few of them are focused on quantification. The purpose of the present work is to set up a suitable and time efficient method able to quantify the extent of tannin protein precipitation. Bradykinin, chosen as a model, was incubated with increasing concentrations of 1,2,3,4,6-penta-O-galloyl-β-d-glucose and tannic acid selected as reference of tannic compounds. Bradykinin not precipitated was determined by a mass spectrometer TSQ Quantum Ultra Triple Quadrupole (direct infusion analysis). The results were expressed as PC₅₀, which is the concentration able to precipitate 50% of the protein. The type of tannin-protein interaction was evaluated also after precipitate solubilisation. The involvement of proline residues in tannin-protein interactions was confirmed by repeating the experiment using a synthesized peptide (RR-9) characterized by the same bradykinin sequence, but having proline residues replaced by glycine residues: no interaction occurred between the peptide and the tannins. Moreover, modelling studies on PGG-BK and PGG-RR-9 were performed to deeply investigate the involvement of prolines: a balance of hydrophobic and H-bond contacts stabilizes the PGG-BK cluster and the proline residues exert a crucial role thus allowing the PGG molecules to elicit a sticking effect.

Effects of supplementing herbaceous forage legume pellets on growth indices and blood profile of West African dwarf sheep fed Guinea grass

Twenty West African dwarf (WAD) rams with average body weight of 12.43 ± 0.5 kg were used for the experiment that lasted 84 days to investigate the effects of supplementing herbaceous forage legume pellets on weight change and blood profile of animals fed Panicum maximum basal diet. Sole Panicum maximum served as the control diet and three other experimental diets were P. maximum supplemented with Lablab purpureus pellets, P. maximum supplemented with Calopogonium mucunoides pellets and P. maximum supplemented with Mucuna pruriens pellets constituted the four treatments which were arranged in a completely randomised design. The rams were divided into four groups of five animals each and were balanced for variation in live weight before they were assigned the experimental diets. Panicum maximum was offered to the animals ad libitum and legume pellets were supplemented. Significant differences (P < 0.05) were observed in weight gain of the rams. Those fed the control diet had the lowest value of 41.88 g/day while rams supplemented L. purpureus pellets had the highest value (83.66 g/day). Haematological parameters, leucocyte values and serum biochemical indices of WAD rams were significantly (P < 0.05) different across the dietary treatments at the final stage of the trial. The values for red blood cells, haemoglobin concentration, packed cell volume and mean corpuscular haemoglobin decreased slightly in rams supplemented with M. pruriens pellets. Reduction of serum biochemical parameters was also noticed in rams supplemented with M. pruriens pellets. It can be concluded that L. purpureus pellets ranked the best among the herbaceous legume pellets as supplemental feed for West African dwarf sheep resulting in higher weight gain and better feed conversion efficiency with no deleterious effect on blood profile.

Altering salivary protein profile can increase acceptance of a novel bitter diet

Bitter taste is often associated with toxins, but accepting some bitter foods, such as green vegetables, can be an important part of maintaining a healthy diet. In rats and humans, repeated exposure to a bitter stimulus increases acceptance. Repeated exposure allows an individual the opportunity to learn about the food's orosensory and postingestive effects. It also alters the salivary protein (SP) profile, which in turn alters taste signaling. We have hypothesized that altering the salivary proteome plays a role in the increased acceptance after repeated exposure. Here we test this and attempt to disentangle the contribution of learning during dietary exposure from the contribution of SPs in increased acceptance of bitter diet. Dietary exposure to quinine or tannic acid and injection of isoproterenol (IPR) result in similar salivary protein profiles. Here we used either the bitter stimulus tannic acid or IPR injection to upregulate a subset of SPs before exposing animals to a novel diet containing quinine (0.375%). Control animals received either a control diet before being exposed to quinine, or a diet containing sucrose octaacetate, a compound that the animals avoid but does not alter SP profiles. The treatments that alter SP expression increased rate of feeding on the quinine diet compared to the control treatments. Additionally, tannic acid exposure altered intake and meal size of the quinine diet. These data suggest that SPs, not just learning about bitter food, increase acceptance of the bitter diet.

Comparative aspects of plant tannins on digestive physiology, nutrition and microbial community changes in sheep and goats: A review

Comparative aspects of plant tannins on digestive physiology, nutrition and microbial community in sheep and goats are discussed in the context of differences due to feed intake, digestibility, utilization of nutrients and microbial community. The purpose of this review was to present an overview of the potential benefits of tannin-containing diets for sheep and goats and specie differences in their response to tannins. It is well established that moderate level of tannins in the diet (3%-4% tannins DM) can precipitate with soluble proteins and increase protein supply to the sheep, but comparative aspects of tannin-containing diets in sheep and goats on animal performance, digestive physiology, rumen microbial changes and potential benefits to sustainable animal production by those compounds have received little attention. In addition, developing plant-based tannin-containing diets for control of rumen microbiota and rumen fermentation (e.g., methane gas) would be expected to have a greater impact on the ruminant health, productivity and emission of greenhouse gasses. The positive impacts of the plant tannin compounds mainly depend on their influence on the gut microbiome diversity and ability to generate fermentation end products (short-chain fatty acids) that have diverse biological roles. Diets which contain optimal levels of tannins have potential benefits for sustainability of small ruminant production systems. However, there is a need for an improved understanding of the utilization of tannin-containing forages to improve their management. This implies investigations of animal responses to tannin-containing forages or browse species and, in particular, a better understanding of the interactions that can arise between sheep and goats on digestion, DMD, rumen fermentation and microbial community changes. This knowledge could help to improve current feeding systems in terms of efficiency of feed use and environmental impacts (reduce methane gas production) and thus contribute to the development of a sustainable sheep and goat production.

Antinutritional factors in foods for livestock

Antinutritional factors in livestock foods may be defined as the substances which either by themselves, or through their metabolic products arising in the system, interfere with food utilization and affect the health and production of animals. These deleterious substances, also referred to as anti-quality factors can be divided tentatively into four groups based on their effects on livestock: (i) affecting protein utilization and depressing digestion (protease inhibitors, tannins, saponins, lectins, etc.), (ii) metal ion scavengers (oxalates, phytates, gossypol pigments, glucosinolates), (Hi) antivitamins, and (iv) those which cannot be put in the above categories (mycotoxins, mimosine, cyanogens, nitrates, alkaloids, photosensitizing agents, isoflavones, etc.). This paper discusses only those deleterious substances which are of prime concern to the farmers and scientists of developing countries. Much emphasis is given to polyphenols compounds, as this class of anti-nutritional factor is the most widespread in non-conventional foodstuffs, i.e. agroindustrial and forestry byproducts. The effective utilization of these non-conventional foods forms the main area of research in the third world countries due to shortages of conventional foods. Efforts have been made to present the current knowledge on their assay methods, effects on animals, mode of action and detoxification/detannification using physical, chemical and biotechnological approaches. Other anti-quality factors viz., mycotoxins, mimosine, cyanogens and nitrates which also cause damage to livestock in developing countries are also discussed briefly.

Salivary tannin-binding proteins are a pervasive strategy used by the folivorous/frugivorous black howler monkey

Dietary tannins can affect protein digestion and absorption, be toxic, and influence food selection by being astringent and bitter tasting. Animals that usually ingest tannins may regularly secrete tannin-binding salivary proteins (TBSPs) to counteract the negative effects of tannins or TBSPs production can be induced by a tannin-rich diet. In the wild, many primates regularly eat a diet that contains tannin-rich leaves and unripe fruit and it has been speculated that they have the physiological ability to cope with dietary tannins; however, details of their strategy remains unclear. Our research details the salivary protein composition of wild and zoo-living black howler monkeys (Alouatta pigra) feeding on natural versus manufactured low-tannin diets, and examines differences in TBSPs, mainly proline-rich proteins (PRPs), to determine whether production of these proteins is dependent on the tannin content of their food. We measured the pH, flow rate, and concentration of total protein and trichloroacetic acid soluble proteins (an index of PRPs) in saliva. Howler monkeys produced slightly alkaline saliva that may aid in the binding interaction between tannin and salivary proteins. We used gel electrophoresis to describe the salivary protein profile and this analysis along with a tannin-binding assay allowed us to detect several TBSPs in all individuals. We found no differences in the characteristics of saliva between wild and zoo-living monkeys. Our results suggest that black howler monkeys always secrete TBSPs even when fed on foods low in tannins. This strategy of constantly using this salivary anti-tannin defense enables them to obtain nutrients from plants that sometimes contain high levels of tannins and may help immediately to overcome the astringent sensation of their food allowing howler monkeys to eat tanniferous plants.

Repeated oral dose toxicity study on hydrolysable tannin rich fraction isolated from fruit pericarps of Terminalia chebula Retz in Wistar albino rats

Terminalia chebula fruits are one of the richest sources of hydrolysable tannins and it is well known medicinal agent in traditional systems of medicine for treatment of various chronic ailments. In the present study, hydrolysable tannin rich fraction (HTF) was isolated from 80% hydroalcoholic extract of Terminalia chebula fruit pericarps and it was studied for acute and repeated dose oral toxicity in Wistar albino rats. HTF did not show any toxic symptoms or mortality at single dose administration of 5000 mg/kg/p.o followed by observation for 14 days. On repeated dose 28 days oral toxicity study, administration of HTF at 1000 mg/kg showed marked reduction in body weight, food intake and water intake when compared with vehicle control. It was also observed that HTF could increase serum urea, glucose and AST level significantly when compared with vehicle control indicating mild disturbances in liver and kidney functions. On histopathological screening, HTF treatment showed a mild granulomatous inflammation in the liver and all other organs remained normal. It was concluded that following 28 days repeated dose oral administration, HTF caused mild disturbances in liver and kidney function which was indicated by reduced body weight, food and water intake, serum parameters and histological observations.

Salivary proteins alter taste-guided behaviors and taste nerve signaling in rat

Taste stimuli are normally dissolved in saliva prior to interacting with their respective receptor targets. There are hundreds of proteins in saliva, and it has been hypothesized that these proteins could interact with either taste stimuli or taste receptors to alter taste signaling and diet acceptance. However, the impact of these proteins on feeding has been relatively unexplored using rodent models. We have developed a novel technique for saliva collection that allows us to link salivary protein expression with feeding behavior. First, we monitored the microstructure of rats' feeding patterns on a 0.375% quinine diet (Q-diet) while tracking changes in salivary protein expression. We found 5 protein bands were upregulated by diet exposure to Q-diet and upregulation of a subset of these bands were statistically related to increased diet acceptance, including changes in behavioral measures that are thought to represent both orosensory and postingestive signaling. In a second experiment, we measured the licking to a range of quinine solutions (0.01-1.0mM) before and after the animals were exposed to a tannic acid diet that altered salivary protein expression. Rats found the quinine solutions less aversive after salivary protein altering diets. In a third experiment we recorded the response of the chorda tympani (CT) nerve while delivering quinine solutions (0.3-30mM) to the front of the tongue dissolved in either "donor saliva" containing salivary proteins or donor saliva which has had the salivary proteins removed. Donor saliva was collected from a separate group of animals using isoproterenol and pilocarpine. The samples containing salivary proteins resulted in lower nerve responses than those without salivary proteins. Together these data suggest that salivary proteins are capable of altering taste-guided behaviors and taste nerve signaling.

Transcriptome analysis reveals molecular anthelmintic effects of procyanidins in C. elegans

Worldwide, more than 1 billion people are affected by infestations with soil-transmitted helminths and also in veterinary medicine helminthiases are a severe threat to livestock due to emerging resistances against the common anthelmintics. Proanthocyanidins have been increasingly investigated for their anthelmintic properties, however, except for an interaction with certain proteins of the nematodes, not much is known about their mode of action. To investigate the anthelmintic activity on a molecular level, a transcriptome analysis was performed in Caenorhabditis elegans after treatment with purified and fully characterized oligomeric procyanidins (OPC). The OPCs had previously been obtained from a hydro-ethanolic (1:1) extract from the leaves of Combretum mucronatum, a plant which is traditionally used in West Africa for the treatment of helminthiasis, therefore, also the crude extract was included in the study. Significant changes in differential gene expression were observed mainly for proteins related to the intestine, many of which were located extracellularly or within cellular membranes. Among the up-regulated genes, several hitherto undescribed orthologues of structural proteins in humans were identified, but also genes that are potentially involved in the worms' defense against tannins. For example, T22D1.2, an orthologue of human basic salivary proline-rich protein (PRB) 2, and numr-1 (nuclear localized metal responsive) were found to be strongly up-regulated. Down-regulated genes were mainly associated with lysosomal activity, glycoside hydrolysis or the worms' innate immune response. No major differences were found between the groups treated with purified OPCs versus the crude extract. Investigations using GFP reporter gene constructs of T22D1.2 and numr-1 corroborated the intestine as the predominant site of the anthelmintic activity. The current findings support previous hypotheses of OPCs interacting with intestinal surface proteins and provide the first insights into the nematode's response to OPCs on a molecular level as a base for the identification of future drug targets.

Effect of Tannic Acid on the Protective Properties of the in situ Formed Pellicle

OBJECTIVES

In the present in situ/ex vivo study the impact of tannic acid on the erosion-protective properties of the enamel pellicle was tested. Additionally, the antiadherent and antibacterial effects of tannic acid were evaluated.

METHODS

The pellicle was formed in situ on bovine enamel samples fixed on individual splints worn by 6 subjects. Following 1 min of pellicle formation the volunteers rinsed for 10 min with tannic acid. After further oral exposure for 19 min, 109 min, and 8 h overnight, respectively, slabs were incubated in HCl ex vivo (pH 2.0, 2.3, 3.0) over 120 s. Subsequently, kinetics of calcium and phosphate release were measured photometrically. Samples after a 1-min fluoride mouth rinse as well as enamel samples with and without a 30-min in situ pellicle served as controls. Antiadherent effects were evaluated after a 1-min rinse with tannic acid and oral exposure of the slabs overnight. DAPI (4',6-diamidino-2-phenylindole) combined with concanavalin A staining and live/dead staining was used for fluorescence microscopic visualization and quantification of adherent bacteria and glucans. Modification of the pellicle's ultrastructure by tannic acid was evaluated by transmission electron microscopy (TEM).

RESULTS

Tannic acid significantly improved the erosion-protective properties of the pellicle in a pH-dependent manner. Bacterial adherence and glucan formation on enamel were significantly reduced after rinses with tannic acid as investigated by fluorescence microscopy. TEM imaging indicated that rinsing with tannic acid yielded a sustainable modification of the pellicle; it was distinctly more electron dense.

CONCLUSION

Tannic acid offers an effective and sustainable approach for the prevention of caries and erosion.

Phytochemicals in animal health: diet selection and trade-offs between costs and benefits

Many plant tissues contain plant secondary compounds (PSC), which have long been recognised as defensive chemicals that deter herbivory via their toxic effects. However, herbivores may also benefit from including PSC into their diets. Plant-derived phenolics, terpenes and alkaloids have antiparasitic properties and sesquiterpene lactones have antibacterial, antifungal and antiparasitic properties. These actions are in part a consequence of the negative actions that PSC exert across several trophic levels, including the bacteria, parasites and fungi that inhabit herbivores' bodies. Given the dual action, toxin and medicine, it is possible to hypothesise that self-selection of PSC by herbivores should occur when the benefits outweigh the costs of PSC ingestion. Recent research suggests that sheep and goats self-medicate against parasitic infections. They increase preference for condensed tannin-containing foods when experiencing a parasitic burden. This behaviour improves health; it is triggered by parasitism and weakens when parasitism subsides. However, the causes underlying these responses are not straightforward when viewed under a unidimensional cost-benefit analysis. This is because the intensity of antinutritional/toxic and medicinal effects of PSC is not static or just dependent upon the isolated post-ingestive effects of single PSC. Nutrient-PSC and PSC-PSC interactions, social models, as well as feeding patterns, all influence the perceived net benefit of incorporating medicines into a diet. A better understanding of the net benefit of self-medication in complex feeding environments will allow for the development of innovative managing strategies aimed at providing the food alternatives and conditions for improving the nutrition, health and welfare of grazing animals.

A study of procyanidin binding to Histatin 5 using Electrospray Ionization Tandem Mass Spectrometry (ESI-MS/MS) and molecular simulations

Tannins act as antioxidants, anticarcinogens, cardio-protectants, anti-inflammatory and anti-microbial agents and bind to salivary peptides by hydrophilic and hydrophobic mechanisms. Electrospray Ionization Mass Spectrometry (ESI-MS) has been used to assess both hydrophilic and hydrophobic components of noncovalent binding in protein complexes. In the present study, direct infusion Electrospray-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ES-FTICR MS) is used to assess relative binding affinities of procyanidin tannin stereoisomers for salivary peptides arising from aqueous solutions. The condensed tannins procyanidin B1, B2, B3, and B4 demonstrate significantly different binding affinities for the salivary peptide Histatin 5. Rigid docking combined with molecular dynamics optimization is used to investigate procyanidin-Histatin 5 binding mechanisms and as a basis to rationalize trends found in the corresponding ES-FTICR MS experiments. The relative binding affinities of the four procyanidin rotamers are different in the gas and liquid phases. The simulation results indicate that many of the same contact points are made in both phases, but there is a increase in strong electrostatic interactions and an decrease in π-π contacts upon transfer from the liquid to the gas phase. The simulations reveal that the tannin interactions can make close contacts with a variety of amino acid residues on the peptide.

Biobutanol production using unhydrolyzed waste acorn as a novel substrate

Clostridium acetobutylicumcells did not grow on untreated acorn powder but they grew and produced acetone, butanol, and ethanol on tannin-free acorn powder.

Multilayer Capsules of Bovine Serum Albumin and Tannic Acid for Controlled Release by Enzymatic Degradation

With the purpose to replace expensive and significantly cytotoxic positively charged polypeptides in biodegradable capsules formed via Layer-by-Layer (LbL) assembly, multilayers of bovine serum albumin (BSA) and tannic acid (TA) are obtained and employed for encapsulation and release of model drugs with different solubility in water: hydrophilic-tetramethylrhodamine-isothiocyanate-labeled BSA (TRITC-BSA) and hydrophobic 3,4,9,10-tetra-(hectoxy-carbonyl)-perylene (THCP). Hydrogen bonding is proposed to be predominant within thus formed BSA/TA films. The TRITC-BSA-loaded capsules comprising 6 bilayers of the protein and polyphenol are benchmarked against the shells composed of dextran sulfate (DS) and poly-l-arginine (PARG) on degradability by two proteolytic enzymes with different cleavage site specificity (i.e., α-chymotrypsin and trypsin) and toxicity for murine RAW264.7 macrophage cells. Capsules of both types possess low cytotoxicity taken at concentrations equal or below 50 capsules per cell, and evident susceptibility to α-chymotrypsin resulted in release of TRITC-BSA. While the BSA/TA-based capsules clearly display resistance to treatment with trypsin, the assemblies of DS/PARG extensively degrade. Successful encapsulation of THCP in the TRITC-BSA/TA/BSA multilayer is confirmed, and the release of the model drug is observed in response to treatment with α-chymotrypsin. The thickness, surface morphology, and enzyme-catalyzed degradation process of the BSA/TA-based films are investigated on a planar multilayer comprising 40 bilayers of the protein and polyphenol deposited on a silicon wafer. The developed BSA/TA-based capsules with a protease-specific degradation mechanism are proposed to find applications in personal care, pharmacology, and the development of drug delivery systems including those intravenous injectable and having site-specific release capability.

Tannin-degrading bacteria with cellulase activity isolated from the cecum of the Qinghai-Tibet plateau zokor (Myospalax baileyi)

Tannins, which are polyphenols present in various plants, have anti-nutritional activity; however, their negative effects are mitigated by the presence of tannin-degrading microorganisms in the gastrointestinal tract of animals. This has never been investigated in the plateau zokor (Myospalax baileyi) – the predominant small herbivore in the alpine meadow ecosystem of Qinghai Province, China – which consumes tannin-rich herbaceous plants. Tannase activity in the feces of the plateau zokor increased from June to August corresponding to the increase in hydrolyzable tannin concentrations in plants during this period, and three tannin-degrading facultative anaerobic strains (designated as E1, E2, and E3) were isolated from the cecum of these animals. Sequencing of the 16S rDNA gene identified isolates of strain E1 as belonging to the genusEnterococcus, and E2 and E3 to the genusBacillus. All of the bacteria had cellulose-degrading capacity. This study provides the first evidence of symbiotic bacterial strains that degrade tannic acid and cellulose in the cecum of plateau zokor.