Effect of reverse osmosis and ultra-high-pressure homogenization on the composition and microstructure of sweet buttermilk

Buttermilk (BM), the by-product of butter making, is similar to skim milk (SM) composition. However, it is currently undervalued in dairy processing because it is responsible for texture defects (e.g., crumbliness, decreased firmness) in cheese and yogurt. One possible way of improving the incorporation of BM into dairy products is by the use of technological pretreatments such as membrane filtration and homogenization. The study aimed at characterizing the effect of preconcentration by reverse osmosis (RO) and single-pass ultra-high-pressure homogenization (UHPH) on the composition and microstructure of sweet BM to modify its techno-functional properties (e.g., protein gel formation, syneresis, firmness). The BM and RO BM were treated at 0, 15, 150, and 300 MPa. Pressure-treated and control BM and RO BM were ultracentrifuged to fractionate them into the following 3 fractions: a supernatant soluble fraction (top layer), a colloidal fraction consisting of a cloudy layer (middle layer), and a high-density pellet (bottom layer). Compositional changes in the soluble fraction [lipid, phospholipid (PL), protein, and salt], as well as its protein profile by PAGE analysis, were determined. Modifications in particle size distribution upon UHPH were monitored by laser diffraction in the presence and absence of sodium citrate to dissociate the casein (CN) micelles. Microstructural changes in pressure-treated and non-pressure-treated BM and RO BM particles were monitored by confocal laser scanning microscopy. Particle size analysis showed that UHPH treatment significantly decreased the size of the milk fat globule membrane fragments in BM and RO BM. Also, pressure treatment at 300 MPa led to a significant increase in the recovery of total lipids, CN, calcium, and phosphate in the BM soluble fraction (top layer) following ultracentrifugation. However, PL were primarily concentrated in the pellet cloud (middle layer), located above the pellet in BM concentrated by RO. In contrast, PL were evenly distributed between soluble and colloidal phases of BM. This study provides insight into the modifications of sweet BM constituents induced by RO and UHPH from a compositional and structural perspective.

A systematic review of breast milk microbiota composition and the evidence for transfer to and colonisation of the infant gut

The intestinal microbiota plays a major role in infant health and development. However, the role of the breastmilk microbiota in infant gut colonisation remains unclear. A systematic review was performed to evaluate the composition of the breastmilk microbiota and evidence for transfer to/colonisation of the infant gut. Searches were performed using PUBMED, OVID, LILACS and PROQUEST from inception until 18th March 2020 with a PUBMED update to December 2021. 88 full texts were evaluated before final critique based on study power, sample contamination avoidance, storage, purification process, DNA extraction/analysis, and consideration of maternal health and other potential confounders. Risk of skin contamination was reduced mainly by breast cleaning and rejecting the first milk drops. Sample storage, DNA extraction and bioinformatics varied. Several studies stored samples under conditions that may selectively impact bacterial DNA preservation, others used preculture reducing reliability. Only 15 studies, with acceptable sample size, handling, extraction, and bacterial analysis, considered transfer of bacteria to the infant. Three reported bacterial transfer from infant to breastmilk. Despite consistent evidence for the breastmilk microbiota, and recent studies using improved methods to investigate factors affecting its composition, few studies adequately considered transfer to the infant gut providing very little evidence for effective impact on gut colonisation.

Mild intermittent hypoxia exposure alters gut microbiota composition in men with overweight and obesity

Results from high altitude studies in humans and controlled animal experiments suggest that hypoxia exposure induces alterations in gut microbiota composition, which may in turn affect host metabolism. However, well-controlled studies investigating the effects of normobaric hypoxia exposure on gut microbiota composition in humans are lacking. The aim of this study was to explore the impact of mild intermittent hypoxia (MIH) exposure on gut microbiota composition in men with overweight and/or obesity. We performed a randomised, single-blind crossover study, in which participants were exposed to MIH (FiO2: 15%, 3×2 h per day) and normoxia (FiO2: 21%) for seven consecutive days. Following the MIH and normoxia exposure regimens, faecal samples were collected for determination of faecal microbiota composition using 16S rRNA gene-amplicon sequencing in the morning of day 8. Paired faecal samples were available for five individuals. Furthermore, tissue-specific insulin sensitivity was determined using the gold-standard two-step hyperinsulinemic-euglycemic clamp. MIH did not affect microbial alpha and beta-diversity but reduced the relative abundance of Christensenellaceae and Clostridiaceae bacterial families. MIH significantly increased the abundances of obligate anaerobic bacterial genera including Fusicatenibacter, Butyricicoccus and Holdemania, whilst reducing Christensenellaceae R-7 group and Clostridium sensu stricto 1, although these findings were not statistically significant after correction for multiple testing. Furthermore, MIH-induced alterations in abundances of several genera were associated with changes in metabolic parameters such as adipose and peripheral insulin sensitivity, plasma levels of insulin, fatty acids, triacylglycerol and lactate, and substrate oxidation. In conclusion, we demonstrate for the first time that MIH exposure induces modest effects on faecal microbiota composition in humans, shifting several bacterial families and genera towards higher abundances of anaerobic butyrate-producing bacteria. Moreover, MIH-induced effects on faecal microbial composition were associated with parameters related to glucose and lipid homeostasis, supporting a link between MIH-induced alterations in faecal microbiota composition and host metabolism. The study was registered at the Netherlands Trial Register: NL7120/NTR7325.

Structure and function of non-digestible carbohydrates in the gut microbiome

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.

A blend of 3 mushrooms dose-dependently increases butyrate production by the gut microbiota

The gut microbiota has been indicated to play a crucial role in health and disease. Apart from changes in composition between healthy individuals and those with a disease or disorder, it has become clear that also microbial activity is important for health. For instance, butyrate has been proven to be beneficial for health, because, amongst others, it is a substrate for the colonocytes, and modulates the host's immune system and metabolism. Here, we studied the effect of a blend of three mushrooms (Ganoderma lucidum GL AM P-38, Grifola frondosa GF AM P36 and Pleurotus ostreatus PO AM-GP37)) on gut microbiota composition and activity in a validated, dynamic, computer-controlled in vitro model of the colon (TIM-2). Predigested mushroom blend at three doses (0.5, 1.0 and 1.5 g/day of ingested mushroom blend) was fed to a pooled microbiota of healthy adults for 72 h, and samples were taken every day for microbiota composition (sequencing of amplicons of the V3-V4 region of the 16S rRNA gene) and activity (short-chain fatty acid (SCFA) production). The butyrate producing genera Lachnospiraceae UCG-004, Lachnoclostridium, Ruminococcaceae UCG-002 and Ruminococcaceae NK4A214-group are all dose-dependently increased when the mushroom blend was fed. Entirely in line with the increase of these butyrate-producers, the cumulative amount of butyrate also dose-dependently increased, to roughly twice the amount compared to the control (medium without mushroom blend) on the high-dose mushroom blend. Butyrate proportionally made up 53.1% of the total SCFA upon feeding the high-dose mushroom blend, compared to 27% on the control medium. In conclusion, the (polysaccharides in the) mushroom blend led to substantial increase in butyrate by the gut microbiota. These results warrant future mechanistic research on the mushroom blend, as butyrate is considered to be one of the microbial metabolites that contributes to health, by increasing barrier function and modulating inflammation.

Lean and obese microbiota: differences in in vitro fermentation of food-by-products

The aim of the study was to investigate the potential prebiotic effects of food-by-products (cassava bagasse (n=3), orange bagasse (n=2) and passion fruit peel (n=3)) using an in vitro model simulating the proximal colon, and to assess possible differences in fermentation when using faecal microbiota from lean or obese people. Fermentation of the by-products was compared to a control medium and the prebiotic inulin. The effects of the by-products on the dynamics of the gut microbiota differed according to the type of microbiota, as well as the type of by-product used. Principal Coordinate Analysis of the microbiota showed evidence of a clear separate clustering of lean and obese microbiota before the addition of substrates, which disappeared after fermentation, and instead, distinct clusters due to primary carbohydrate composition of the by-products (starch, fructan and pectin) were present. This is evidence that the substrates drove the obese microbiota to a healthier profile, more similar to that of the lean microbiota. Cassava bagasses enriched the beneficial genus Bifidobacterium in the obese microbiota. The production of total SCFA by cassava bagasses by the obese microbiota was higher than for control medium and inulin. Orange bagasses stimulated the growth of the butyrate-producing genus Coprococcus. Passion fruit peels were poorly fermented and generated negligible amounts of intermediate metabolites, indicating slow fermentation. Nevertheless, passion fruit peel fermentation resulted in a microbiota with the highest diversity and evenness, a positive trait regarding host health. In conclusion, the use of food-by-products could be an important step to tackle obesity and decrease the waste of valuable food material and consequently environmental pollution. They are an inexpensive and non-invasive way to be used as a dietary intervention to improve health, as they were shown here to drive the composition of the obese microbiota to a healthier profile.

Bioconversion of polyphenols and organic acids by gut microbiota of predigested Hibiscus sabdariffa L. calyces and Agave (A. tequilana Weber) fructans assessed in a dynamic in vitro model (TIM-2) of the human colon

The present work aimed at understanding gut microbiota bioconversion of phenolic compounds (PC) and organic acids in predigested Hibiscus sabdariffa (Hb) calyces and the mixture of Hb and Agave (Agave tequilana Weber) fructans (AF). With this purpose, dried Hb and Hb/AF were predigested with enzymatic treatment, and then fermented in a dynamic in vitro model of the human colon (TIM-2). After HPLC-ESI-QToF-MS analysis of samples taken at 0, 24, 48 and 72 h of fermentation, it was observed that hydroxycinnamic acids, flavanols, flavonols, and anthocyanins were mainly transformed into derivatives of hydroxyphenylpropionic, hydroxyphenylacetic and hydroxybenzoic acids. Moreover, organic acids, such as hydroxycitric and hibiscus acids, were formed along with unidentified lactones and reduced compounds. Interestingly, no differences were observed between microbial-derived metabolites formed after the fermentation of Hb and Hb/AF. In conclusion, colonic fermentation of polyphenol-rich Hb yields a wide range of microbial phenolic metabolites with potential effects on health.

Polysaccharide source altered ecological network, functional profile, and short-chain fatty acid production in a porcine gut microbiota

Several validated dynamic in vitro models of the colon have been developed for humans, but there is no dynamic in vitro fermentation model for pigs. This study was conducted to modify the human, dynamic, computer-controlled TNO in vitro model of the colon (TIM-2) for pigs and investigate effects of different starch sources and polysaccharides on swine microbiota structure, ecological network, predictive functional profile, and short-chain fatty acids production. Our study showed that three different types of starch or two polysaccharides greatly impacted microbiota composition. Co-occurrence network analysis indicated that microbiota fed with different sources of starch changed the network topological properties. Functional profiles were predicted to vary significantly among the three starch treatments, and the original pig faecal inoculum was more similar to maize starch treatment. On the other hand, compared with maize starch and arabinoxylans (AX), the microbial composition of the original inoculum was more similar when AX-XG (arabinoxylans and xyloglucan) were added, and the functional profile of the original inoculum also clustered with AX-XG. The cumulative production of acetic, propionic, and butyric acid on maize starch were significantly higher than those on potato starch and wheat starch, while only the amount of acetic acid was significant higher on AX-XG than that on AX. In conclusion, supplementation of maize starch as the starch source together with AX and XG, leads to the bacteria being more stable in the in vitro model and closer to the original inoculum and microbial function compared to potato starch, wheat starch and AX. A maize basal diet may improve energy absorption in the large intestine in growing pigs.

Survival of a probiotic-containing product using capsule-within-capsule technology in an in vitro model of the stomach and small intestine (TIM-1)

The aim of the research was to compare the survival of a blend of five probiotic strains (2 bifidobacteria and 3 lactobacilli) in a capsule within capsule (Duocap^®) containing Ahiflower^® oil, as compared to the strains in the powder (with or without Ahiflower oil), or the strains when present in the inner capsule only. This was tested in a validated, dynamic in vitro model of the stomach and small intestine (TIM-1), simulating human adults. Experiments were performed both in the gastric compartment of the model, as well as in the complete system (stomach + small intestine). Survival of the strains after transit through the gastric compartment in the Duocap capsule was higher by about a factor of 1.5 compared to the other 3 variables. In these gastric experiments, the Ahiflower oil did not seem to have an additional benefit, in the sense that it did not increase survival over the strains alone. After transit through the complete gastrointestinal tract survival was approximately 2-fold higher for the strains within the Duocap capsule, compared to the strains within the inner capsule or the powder. In these experiments, Ahiflower oil did have an additional benefit. The survival of the strains in the combination of powder with Ahiflower oil showed a similar survival as that of the Duocap, although in the first few hours of the experiments survival of both species lagged behind, and only caught up at the end of the test. In conclusion, the developed capsule-in-capsule technology increased the amount of viable cells in the upper gastrointestinal tract, mainly due to the presence of the polyunsaturated fatty acids contained in the outer capsule, which particularly protected the blend of probiotics in the small intestine.

Xylo-oligosaccharides from sugarcane show prebiotic potential in a dynamic computer-controlled in vitro model of the adult human large intestine

The aim of the study was to investigate the prebiotic potential of xylo-oligosaccharides (XOS) from sugarcane in a validated, dynamic, computer-controlled in vitro model of the colon (TIM-2) simulating human adults. In two sets of experiments, each with a different microbiota, 3 different doses of XOS were tested at 1.0 g/day, 1.5 g/day and 3.0 g/day. The in vitro model was run for 72 h, and at the start and subsequently every 24 h samples were taken and analysed for short-chain fatty acids (SCFA) and gut microbiota composition. SCFA were analysed using ion chromatography, whereas microbiota composition was analysed using sequencing of the V3-V4 region of the 16S rRNA gene. XOS showed a similar SCFA production per gram of substrate as the control medium, including butyrate, which is considered to be important for gut health. In both sets of experiments XOS showed a consistent dose-dependent increase in abundance over time of the genus Bifidobacterium, and within that of the species B. adolescentis and an unidentified species (labelled 'sp.1'). The results show the potential prebiotic effect of XOS from sugarcane, by its capacity to generate butyrate and increase the health-beneficial bifidobacteria.

Probiotic survival during a multi-layered tablet development as tested in a dynamic, computer-controlled in vitro model of the stomach and small intestine (TIM-1)

The aim of the research was to develop a galenical formulation for the combination of the three probiotic strains Lactobacillus gasseri PA 16/8, Bifidobacterium longum SP 07/3 and Bifidobacterium bifidum MF 20/5 that would lead to the presence of a high amount of viable cells in the small intestine, the presumed site of action of these strains. This was tested in a validated, dynamic in vitro model of the stomach and small intestine (TIM‐1), simulating human adults after intake of a meal. Experiments were performed both in the gastric compartment of the model, as well as in the complete system (stomach + small intestine). Survival of the strains in an unformulated probiotic powder after transit through the gastric compartment was 5·3% for the bifidobacteria and 1% for L. gasseri. After transit through the complete gastrointestinal tract, this dropped to 2% for bifidobacteria and 0·1% for Lactobacillus. After several rounds of optimization, an enteric‐coated tablet was developed that increased the delivery of viable cells reaching the small intestine to 72% (gastric survival) for bifidobacteria, and 53% (gastric) for L. gasseri. Also survival in the small intestine increased by about an order of magnitude. The final galenical formulation was tested in two applications: adults and elderly, both of which have their own physiological parameters. These experiments corroborated the results obtained in the development phase of the project. In conclusion, the developed enteric coating led to a 20‐ to 40‐fold increase in the delivery of viable cells to the small intestine.

Significance and Impact of the Study

Predictive GI in vitro models are very helpful and reliable tools for the development of new galenical formula containing probiotics, and in the current example helped to deliver >10‐fold higher numbers of viable cells to the small intestine, presumably leading to improved functionality of the strains.

Effects of functional pasta ingredients on different gut microbiota as revealed by TIM-2 in vitro model of the proximal colon

Diet-related modulation of gut microbiota and its metabolic activity represents an intriguing research context, particularly in the case of disorders related to imbalances in gut microbial communities. We here explored the effects of Bacillus coagulans GBI-30, 6086 (BC30), β-glucans, and innovative whole-grain pastas, with or without these functional ingredients, on gut microbiota from three groups of children, presenting different susceptibility to type 1 diabetes, by using the well-controlled TNO in vitro model of the proximal colon (TIM-2). Short- and branched-chain fatty acids production and microbiota composition were assessed by means of gas chromatography and 16S rRNA gene profiling, respectively. In most cases, in vitro dietary interventions caused microbiota-dependent modulations as a result of intergroup variability, but also specific changes in microbial groups were shared between the three microbiotas, highlighting specific diet-microbial taxa connections.

Microbiota composition of dadih - a traditional fermented buffalo milk of West Sumatra

Dadih is an Indonesian traditional spontaneously fermented buffalo milk, produced in West-Sumatra, which is nutritious and has health benefits. The mechanism of action behind the health benefits is largely unknown, but several probiotic strains have been isolated from dadih, which may contribute to its health properties. To identify the composition of its microbiota, two artisanal dadih samples (n = 8) were collected from four producers. The raw buffalo milk used for fermentation was either pasteurized (n = 4) or not (n = 4), and back-slopping was used as a starter-culture (n = 5) or not (n = 3). DNA was extracted from each sample in duplicate and the microbiota composition was determined by 16S-rRNA-gene amplicon-sequencing of the V3-V4 region. PCoA analysis showed clear separation of the samples by producer, but no separation due to pasteurization or use of back-slopping. Lactococcus (52-83%) predominated in all samples, followed by Klebsiella (5-26%), and Lactobacillaceae, Bifidobacterium (particularly high (c. 18%) in the non-pasteurized, back-slopped product from Palupuh), Streptococcus and Leuconostoc. Back-slopping practice correlated significantly with higher abundance of Lactobacillaceae, Pediococcus, species of the order Burkholderiales, and Serratia, but with lower abundance of several other Enterobacteriaceae (including Klebsiella), Streptococcaceae, Staphylococcus and Brachybacterium. Pasteurization was not significantly correlated with the presence of certain members of the final microbiota. Taken together, fermentation results differ significantly from producer to producer and back-slopping practice would be advisable. SIGNIFICANCE AND IMPACT OF THE STUDY: Using state-of-the-art methods we determined the microbiota composition of dadih, an artisanal, traditional fermented buffalo milk of West Sumatra with health benefits. We show that the artisanal practice leaves room for standardization and optimization with respect to the presence of potential pathogenic species in the final product. The Dadih Initiative in Indonesia aims to expand production of this health promoting product, and the findings help to determine important steps for potential food safety issues and good-manufacturing-practices to obtain a safe, nutritious and healthy traditional yoghurt-like functional food.

Spores of Bacillus coagulans GBI-30, 6086 show high germination, survival and enzyme activity in a dynamic, computer-controlled in vitro model of the gastrointestinal tract

The aim of this study was to assess the germination, survival and metabolic activity of the probiotic Bacillus coagulans GBI-30, 6086 [GanedenBC³⁰] (BC30) in a dynamic, computer controlled in vitro model of the gastrointestinal (GI) tract, simulating human adults. Experiments were performed in the presence of a meal to maximise germination, due to the presence of germination-triggers. Both an upper GI tract (stomach and small intestine; TIM-1) and a colon model (TIM-2) were used, where material exiting TIM-1 was added to TIM-2. Spores of BC30 were introduced in the gastric compartment of TIM-1 and samples were taken immediately after the pylorus. Moreover, for 6 h, every hour the ileal efflux was collected and a subsample was plated for viable counts (spores and germinated cells). The remainder of the sample was fed to TIM-2, and after 24 h another sample was taken and tested for viable counts. In addition, samples were taken from the dialysates of the model and analysed using LC-MS/MS to determine bacterial metabolites and digestion products. Survival after transit through the gastric compartment was high (97%) and most cells were still in the spore form (76%). Survival after transit through TIM-1 was on average 51%, meaning that on average half of the orally provided spores was found back as cfu on the agar plates. Of these on average 93% were germinated cells and only 7% were spores. 24 h after the start of the experiments germination had increased in TIM-2 to 97% vegetative cells, and only 3% spores. No further loss of viability was observed in TIM-2. In terms of metabolic activity, increased levels of amino acids, dipeptides and citric acid cycle metabolites were found compared to experiments in the absence of BC30. In conclusion, BC30 spores germinate to a large extent (>90%) in the presence of germination triggers in the small intestine in a model that closely mimics the physiological conditions of human adults. Of the oral dose, as much as half of the cells survived transit through the upper GI tract, and based on the metabolite profile, these cells were metabolically active. Either these cells or the enzymes released from the dead cells aided in digestion of the meal. These insights help explain some of the observations in previous experiments, and support the understanding of the mechanism of action of the probiotic BC30.

Microencapsulation increases survival of the probiotic Lactobacillus plantarum IS-10506, but not Enterococcus faecium IS-27526 in a dynamic, computer-controlled in vitro model of the upper gastrointestinal tract

AIM

To test the effect of microencapsulation on the survival of two probiotic strains isolated from Dadih, Indonesian fermented buffalo milk, in a dynamic, computer-controlled in vitro model of the upper gastrointestinal (GI) tract (TIM-1), simulating human adults.

METHODS AND RESULTS

Free or microencapsulated probiotics, Lactobacillus plantarum IS-10506 or Enterococcus faecium IS-27526, resuspended in milk were studied for survival in the complete TIM-1 system (stomach + small intestine) or in the gastric compartment of TIM-1 only. Hourly samples collected after the ileal-caecal valve or after the pylorus were plated on MRS agar (for Lactobacillus) or S&B agar (for Enterococcus). Survival of the free cells after transit through the complete TIM-1 system was on average for the E. faecium and L. plantarum 15·0 and 18·5% respectively. Survival of the microencapsulated E. faecium and L. plantarum was 15·7 and 84·5% respectively. The free cells were further assessed in only the gastric compartment of TIM-1. E. faecium and L. plantarum showed an average survival of 39 and 32%, respectively, after gastric passage.

CONCLUSION

There is similar sensitivity to gastric acid as well as survival after complete upper GI tract transit of free cells, but microencapsulation only protected L. plantarum.

SIGNIFICANCE AND IMPACT OF STUDY

Survival of microencapsulated L. plantarum IS-10506 is increased compared to free cells in a validated in vitro model of the upper GI tract. It increases its use as an ingredient of functional foods.

Bacillus coagulans GBI-30, 6086 increases plant protein digestion in a dynamic, computer-controlled in vitro model of the small intestine (TIM-1)

The aim of this study was to assess the potential of the probiotic Bacillus coagulans GBI-30, 6086 [GanedenBC30] (BC30) to aid in protein digestion of alimentary plant proteins. To test this, three plant proteins, from pea, soy and rice, were digested in a validated in vitro model of the stomach and small intestine (TIM-1) in the absence and in the presence of BC30. Samples were taken from the TIM-1 fractions that mimic uptake of amino acids by the host and analysed for α-amino nitrogen (AAN) and total nitrogen (TN). Both were increased by BC30 for all three plant proteins sources. The ratio of TN/AAN indicated that for pea protein digestion was increased by BC30, but the degree of polymerisation of the liberated small peptides and free amino acids was not changed. For soy and rice, however, BC30 showed a 2-fold reduction in the TN/AAN ratio, indicating that the liberated digestion products formed during digestion in the presence of BC30 were shorter peptides and more free amino acids, than those liberated in the absence of BC30. As BC30 increased protein digestion and uptake in the upper gastrointestinal (GI) tract, it consequently also reduced the amount of protein that would be delivered to the colon, which could there be fermented into toxic metabolites by the gut microbiota. Thus, the enhanced protein digestion by BC30 showed a dual benefit: enhanced amino acid bioavailability from plant proteins in the upper GI tract, and a healthier environment in the colon.

Challenges in simulating the human gut for understanding the role of the microbiota in obesity

There is an elevated incidence of cases of obesity worldwide. Therefore, the development of strategies to tackle this condition is of vital importance. This review focuses on the necessity of optimising in vitro systems to model human colonic fermentation in obese subjects. This may allow to increase the resolution and the physiological relevance of the information obtained from this type of studies when evaluating the potential role that the human gut microbiota plays in obesity. In light of the parameters that are currently used for the in vitro simulation of the human gut (which are mostly based on information derived from healthy subjects) and the possible difference with an obese condition, we propose to revise and improve specific standard operating procedures.

Reduced engagement with social stimuli in 6-month-old infants with later autism spectrum disorder: a longitudinal prospective study of infants at high familial risk

Background

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects more than 1 % of the population and close to 20 % of prospectively studied infants with an older sibling with ASD. Although significant progress has been made in characterizing the emergence of behavioral symptoms of ASD, far less is known about the underlying disruptions to early learning. Recent models suggest that core aspects of the causal path to ASD may only be apparent in early infancy. Here, we investigated social attention in 6- and 12-month-old infants who did and did not meet criteria for ASD at 24 months using both cognitive and electrophysiological methods. We hypothesized that a reduction in attention engagement to faces would be associated with later ASD.

Methods

In a prospective longitudinal design, we used measures of both visual attention (habituation) and brain function (event-related potentials to faces and objects) at 6 and 12 months and investigated the relationship to ASD outcome at 24 months.

Results

High-risk infants who met criteria for ASD at 24 months showed shorter epochs of visual attention, faster but less prolonged neural activation to faces, and delayed sensitization responses (increases in looking) to faces at 6 months; these differences were less apparent at 12 months. These findings are consistent with disrupted engagement of sustained attention to social stimuli.

Conclusions

These findings suggest that there may be fundamental early disruptions to attention engagement that may have cascading consequences for later social functioning.

Electronic supplementary material

The online version of this article (doi:10.1186/s11689-016-9139-8) contains supplementary material, which is available to authorized users.

Alterations in mucosal neuropeptides in patients with irritable bowel syndrome and ulcerative colitis in remission: a role in pain symptom generation?

BACKGROUND

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by chronic abdominal pain. The transient receptor potential vanilloid 1 (TRPV1) channel, which is involved in visceral pain signalling, has been shown to be up-regulated in IBS. Activation of TRPV1 leads to the release of neuropeptides, such as somatostatin and substance P (SP). We hypothesized that increased pain perception in IBS could be explained by increased transcription in TRPV1 and/or altered levels of neuropeptides. We therefore assessed the transcription of TRPV1 and the mucosal concentration of somatostatin and SP in IBS in comparison to healthy volunteers and patients with ulcerative colitis (UC) in remission as disease controls, and to ascertain their relationship to pain symptoms.

METHOD

Sigmoid colonic mucosal samples were collected from 12 patients with IBS, 34 patients with UC in remission and 9 healthy volunteers, in which groups TRPV1 mRNA levels were determined using quantitative polymerase chain reaction and neuropeptide concentrations by radioimmunoassay. Pain symptom intensity was determined by questionnaires.

RESULTS

Transcription of TRPV1 as well as the concentration of neuropeptides were significantly higher in IBS, but only the former correlated with pain symptom severity.

CONCLUSION

Increased transcription of TRPV1 may provide a possible explanation for pain generation in IBS. While the neuropeptides SP and somatostatin were both found to be increased in IBS, these changes are not sufficient to explain pain generation. Pain generation in IBS is probably explained by a complex redundancy in the regulation of local nociceptive mechanisms, which remains a subject of intensive investigation.

Influence of Bacillus subtilis C-3102 on microbiota in a dynamic in vitro model of the gastrointestinal tract simulating human conditions

Survival and germination rate of Bacillus subtilis C-3102 spores were investigated in a stomach and small intestine model (TIM-1), while the impact of C-3102 cells that had passed through TIM-1 on human colon microbiota was evaluated in a model of the large intestine (TIM-2). The survival of C-3102 spores in TIM-1 was 99%; 8% of the spores had germinated. Effluent of TIM-1 was subsequently introduced into TIM-2 and a micro-array platform was employed to assess changes in the microbiota composition. The effluent, which contained germinated C-3102 cells, increased some Bifidobacterium species and decreased some Clostridium groups. These changes were greater compared to those obtained by adding C-3102 spores directly to TIM-2. The present study suggests that oral doses of B. subtilis C-3102 spores have the potential to modulate the human colon microbiota. This effect may be caused by germination of the spores in the gastrointestinal tract.

Measuring non-steady-state metabolic fluxes in starch-converting faecal microbiota in vitro

This paper explores human gut bacterial metabolism of starch using a combined analytical and computational modelling approach for metabolite and flux analysis. Non-steady-state isotopic labelling experiments were performed with human faecal microbiota in a well-established in vitro model of the human colon. After culture stabilisation, [U-13C] starch was added and samples were taken at regular intervals. Metabolite concentrations and 13C isotopomeric distributions were measured amongst other things for acetate, propionate and butyrate by mass spectrometry and NMR. The vast majority of metabolic flux analysis methods based on isotopomer analysis published to date are not applicable to metabolic non-steady-state experiments. We therefore developed a new ordinary differential equation-based representation of a metabolic model of human faecal microbiota to determine eleven metabolic parameters that characterised the metabolic flux distribution in the isotope labelling experiment. The feasibility of the model parameter quantification was demonstrated on noisy in silico data using a downhill simplex optimisation, matching simulated labelling patterns of isotopically labelled metabolites with measured metabolite and isotope labelling data. Using the experimental data, we determined an increasing net label influx from starch during the experiment from 94±1 µmol/l/min to 133±3 µmol/l/min. Only about 12% of the total carbon flux from starch reached propionate. Propionate production mainly proceeded via succinate with a small contribution via acrylate. The remaining flux from starch yielded acetate (35%) and butyrate (53%). Interpretation of 13C NMR multiplet signals further revealed that butyrate, valerate and caproate were mainly synthesised via cross-feeding, using acetate as a co-substrate. This study demonstrates for the first time that the experimental design and the analysis of the results by computational modelling allows the determination of time-resolved effects of nutrition on the flux distribution within human faecal microbiota in metabolic non-steady-state.

The effects of butyrate enemas on visceral perception in healthy volunteers

Fermentation of dietary fibres by colonic microbes leads to the production of short chain fatty acids (mainly propionate, butyrate and acetate), which are utilized by the colonic mucosa. Previous studies showed positive effects of butyrate on parameters of oxidative stress, inflammation and apoptosis. Recent studies in rats, however, showed that butyrate increased visceral sensitivity. The aim of this study was to determine the effects of physiologically relevant concentrations of butyrate on visceral perception in healthy human subjects. Eleven healthy volunteers participated in this randomized double-blind, placebo controlled cross-over study. The study consisted of three periods of 1 week each, in which the volunteers daily self-administered rectal enemas containing 100, 50 mmol L(-1) butyrate, or placebo (saline) prior to sleeping. A rectal barostat measurement was performed at the start and the end of each test period for the measurement of pain, urge and discomfort. Butyrate treatment resulted in a dose-dependent reduction of pain, urge and discomfort throughout the entire pressure range of the protocol. At a pressure of 4 mmHg, 50 and 100 mmol L(-1) butyrate concentrations resulted in a 23.9% and 42.1% reduction of pain scores, respectively, and the discomfort scores decreased by 44.2% and 69.0% respectively. At a pressure of 67 mmHg, 50 and 100 mmol L(-1) of butyrate decreased the pain scores by 23.8% and 42%, respectively, and discomfort scores 1.9% and 5.2% respectively. Colonic administration of butyrate, at physiologically relevant concentrations, dose-dependently decreases visceral sensitivity in healthy volunteers.

The role of colonic metabolism in lactose intolerance

Lactose maldigestion and intolerance affect a large part of the world population. The underlying factors of lactose intolerance are not fully understood. In this review, the role of colonic metabolism is discussed, i.e. fermentation of lactose by the colonic microbiota, colonic processing of the fermentation metabolites and how these processes would play a role in the pathophysiology of lactose intolerance. We suggest that the balance between the removal and production rate of osmotic-active components (lactose, and intermediate metabolites, e.g. lactate, succinate, etc.) in the colon is a key factor in the development of symptoms. The involvement of the colon may provide the basis for designing new targeted strategies for dietary and clinical management of lactose intolerance.

Genetic analysis of Na(+) and K (+) concentrations in leaf and stem as physiological components of salt tolerance in Tomato

The sodium and potassium concentrations in leaf and stem have been genetically studied as physiological components of the vegetative and reproductive development in two populations of F(8) lines, derived from a salt sensitive genotype of Solanum lycopersicum cv. Cerasiforme, as female parent, and two salt tolerant lines, as male parents, from S. pimpinellifolium, the P population (142 lines), and S. cheesmaniae, the C population (116 lines). Genetic parameters of ten traits under salinity and five of them under control conditions were studied by ANOVA, correlation, principal component and QTL analysis to understand the global response of the plant. Two linkage maps including some tomato flowering time and salt tolerance candidate genes encoding for SlSOS1, SlSOS2, SlSOS3, LeNHX1, LeNHX3, were used for the QTL detection. Thirteen and 20 QTLs were detected under salinity in the P and C populations, respectively, and four under control conditions. Highly significant and contributing QTLs (over 40%) for the concentrations of Na(+) and K(+) in stems and leaves have been detected on chromosome 7 in both the populations. This is the only genomic position where the concentration QTLs for both the cations locate together. The proportion of QTLs significantly affected by salinity was larger in the P population (64.3%, including all QTLs detected under control) than in the C population (21.4%), where the estimated genetic component of variance was larger for most traits. A highly significant association between the leaf area and fruit yield under salinity was found only in the C population, which is supported by the location of QTLs for these traits in a common region of chromososome C1. As far as breeding for salt tolerance is concerned, only two sodium QTLs (lnc1.1 and lnc8.1) map in genomic regions of C1 and C8 where fruit yield QTLs are also located but in both the cases the profitable allele corresponds to the salt sensitive, cultivated species. One of those QTLs, lnc1.1 might involve LeNHX3.

Review article: the role of butyrate on colonic function

BACKGROUND

Butyrate, a short-chain fatty acid, is a main end-product of intestinal microbial fermentation of mainly dietary fibre. Butyrate is an important energy source for intestinal epithelial cells and plays a role in the maintenance of colonic homeostasis.

AIM

To provide an overview on the present knowledge of the bioactivity of butyrate, emphasizing effects and possible mechanisms of action in relation to human colonic function.

METHODS

A PubMed search was performed to select relevant publications using the search terms: 'butyrate, short-chain fatty acid, fibre, colon, inflammation, carcinogenesis, barrier, oxidative stress, permeability and satiety'.

RESULTS

Butyrate exerts potent effects on a variety of colonic mucosal functions such as inhibition of inflammation and carcinogenesis, reinforcing various components of the colonic defence barrier and decreasing oxidative stress. In addition, butyrate may promote satiety. Two important mechanisms include the inhibition of nuclear factor kappa B activation and histone deacetylation. However, the observed effects of butyrate largely depend on concentrations and models used and human data are still limited.

CONCLUSION

Although most studies point towards beneficial effects of butyrate, more human in vivo studies are needed to contribute to our current understanding of butyrate-mediated effects on colonic function in health and disease.

A low perfusion rate microreactor for continuous monitoring of enzyme characteristics: application to glucose oxidase

This report describes a versatile and robust microreactor for bioactive proteins physically immobilized on a polyether sulfone filter. The potential of the reactor is illustrated with glucose oxidase immobilized on a filter with a cut-off value of 30 kDa. A flow-injection system was used to deliver the reactants and the device was linked on-line to an electrochemical detector. The microreactor was used for on-line preparation of apoglucose oxidase in strong acid and its subsequent reactivation with flavin adenine dinucleotide. In addition we describe a miniaturized version of the microreactor used to assess several characteristics of femtomole to attomole amounts of glucose oxidase. A low negative potential over the electrodes was used when ferrocene was the mediator in combination with horseradish peroxidase, ensuring the absence of oxidation of electro-active compounds in biological fluids. A low backpressure at very low flow rates is an advantage, which increases the sensitivity. A variety of further applications of the microreactor are suggested.

Figure

Application of liquid chromatography–mass spectrometry to measure the concentrations and study the synthesis of short chain fatty acids following stable isotope infusions

A new method involving zinc sulphate deproteinization was developed to study short chain fatty acids (SCFA) production in the colon and subsequent occurrence of SCFA in blood. SCFA were baseline separated in a 30 min cycle using ion-exclusion chromatography and detected by mass spectrometry. Concentrations could be measured down to 10 microM and isotopomeric distributions could be assessed, enabling the conduction of tracer studies to study changes in SCFA synthesis. The applicability of the method was tested in an extensively characterized pig model yielding portal SCFA concentrations ranging from 70 microM (butyric acid) to 150 microM (propionic acid) to 440 microM (acetic acid) prior to butyrate tracer infusion, reaching butyric acid isotopic steady state within 2 h.

DNA analysis of the genes encoding acidocin LF221 A and acidocin LF221 B, two bacteriocins produced by Lactobacillus gasseri LF221

Lactobacillus gasseri LF221, an isolate from the feces of a child, produces two bacteriocins. Standard procedures for molecular techniques were used to locate, clone and sequence the fragments of LF221 chromosomal DNA carrying the acidocin LF221 A and B structural genes, respectively. Sequencing analysis revealed the gene of acidocin LF221 A to be an open reading frame encoding a protein composed of 69 amino acids, including a 16-amino-acid N-terminal extension. The acidocin LF221 B gene was found to encode a 65-amino-acid bacteriocin precursor with a 17-amino-acid N-terminal leader peptide. DNA homology searches showed similarities of acidocin LF221 A to brochocin B, lactococcin N and thermophilin B, whereas acidocin LF221 B exhibited some homology to lactacin F and was virtually identical to gassericin X. The peptides encoded by orfA1 and orfB3 showed characteristics of class II bacteriocins and are suspected to be the complementary peptides of acidocin A and B, respectively. orfA3 and orfB5 are proposed to encode putative immunity proteins for the acidocins. Acidocin LF221 A and acidocin LF221 B are predicted to be members of the two-component class II bacteriocins, where acidocin LF221 A appears to be a novel bacteriocin. L. gasseri LF221 is being developed as a potential probiotic strain and a food/feed preservative. Detailed characterization of its acidocins is an important piece of background information useful in applying the strain into human or animal consumption. The genetic information on both acidocins also enables tracking of the LF221 strain in mixed populations and complex environments.

[Biosensors for continuous glucose and lactate monitoring]

Biosensors, and in particular glucose and lactate sensors, are being widely developed and a few have been registered for continuous and semi-continuous use. Three glucose sensors, a transcutaneous sensor (GlucoWatch), a needle sensor (MiniMed) and microdialysis sensor (GlucoDay) have recently been evaluated among diabetes patients. The precise relationship between the biosensor signal and blood glucose is still a problem. For example, the utility of the subcutaneously placed needle sensor to detect nocturnal hypoglycaemia has been shown to be limited. The best subcutaneous site for placing the sensor needs to be systematically investigated. The three types of sensors have only been tested for a 3-5 day period. The utility of the microdialysis (separate from a direct link to biosensors) sensors among diabetes patients was established over a 3-week period following subcutaneous implantation. Furthermore, biosensors are being developed to monitor lactate in preterm babies, and patients with ischaemia, sepsis, or threatened organ damage (e.g. heart and brain infarction). In view of the current progress it is expected that within 5 years biosensor technology will have developed far enough to be used in the management of diabetes and in intensive care units.

Effects of feed deprivation and transport on preslaughter blood metabolites, early postmortem muscle metabolites, and meat quality

In practice, poultry have their feed with drawn several hours before being collected and put on transport to the slaughter plant. With the exhaustion of their internal energy stores, the chickens may lack energy to cope with the conditions to which they are subjected. Meat quality is affected by the energy stored in the muscle at time of slaughter and its rate of decrease postmortem. Of 320 broiler chickens, half were subjected to 5 h feed deprivation whereas the others had access to feed until transport. In both groups, half the chickens were transported for 1.5 h, and the rest were transported within 5 min to the on-site slaughter facility. Twenty chickens were equipped with an ultrafiltration-collection device for monitoring glucose and lactate profiles. After slaughter, liver pH was measured. Stimulation of muscle metabolism was minimized by avoiding plucking. Breast muscle samples were taken at 0, 1, 2, 4, and 6 h and analyzed for pH and metabolite concentrations, and meat quality was measured at 96 h. Although liver glycogen was depleted in feed-deprived chickens, feed deprivation and transport for short periods were not found to affect blood glucose or lactate levels nor glycogen levels in the muscle at slaughter. Muscle carbohydrate metabolism was found to come to a complete halt after 6 h, which was not caused by exhaustion of the glycogen store but by the muscle's ability to generate adenosine triphosphate (ATP) after 4 h. At this time, rigor mortis had set in and deboning could be done without risk of cold shortening.

Molecular cloning and characterisation of three new ATP-binding cassette transporter genes from the wheat pathogen Mycosphaerella graminicola

Three single copy ATP-binding cassette (ABC) transporter encoding genes, designated MgAtr3, MgAtr4, and MgAtr5, were cloned and sequenced from the plant pathogenic fungus Mycosphaerella graminicola. The encoded ABC proteins all exhibit the [NBD-TMS(6)](2) configuration and can be classified as novel members of the pleiotropic drug resistance (PDR) class of ABC transporters. The three proteins are highly homologous to other fungal and yeast, ABC proteins involved in multidrug resistance or plant pathogenesis. MgAtr4 and MgAtr5 possess a conserved ABC motif at both the N- and C-terminal domain of the protein. In contrast, the Walker A motif in the N-terminal and the ABC signature in the C-terminal domain of MgAtr3, deviate significantly from the consensus sequence found in other members of the PDR class of ABC transporters. Expression of MgAtr3 could not be detected under any of the conditions tested. However, MgAtr4 and MgAtr5 displayed distinct expression profiles when treated with a range of compounds known to be either substrates or inducers of ABC transporters. These included synthetic fungitoxic compounds, such as imazalil and cyproconazole, natural toxic compounds, such as the plant defence compounds eugenol and psoralen, and the antibiotics cycloheximide and neomycin. The expression pattern of the genes was also dependent on the morphological state of the fungus. The findings suggest a role for MgAtr4 and MgAtr5 during plant pathogenesis and in protection against toxic compounds.

Monitoring arterio-venous differences of glucose and lactate in the anesthetized rat with or without brain damage with ultrafiltration and biosensor technology

Continuous monitoring of arterio-venous glucose and lactate differences may serve as a diagnostic tool to assess normal brain function and brain pathology. We describe a method and some results obtained with arterio-venous measurements of glucose and lactate in the blood of the halothane-anesthetized rat and after brain injury. The method is based on low flow rate ultrafiltration for continuous collection of blood filtrate combined with flow injection analysis and biosensors for the detection of glucose and lactate. We measured the glucose and lactate concentration every minute in the jugular vein and the aorta at control conditions and during and after inflation of an embolectomy-balloon for 2 min. Net cerebral lactate efflux and glucose uptake was seen under control conditions and at low blood lactate levels. During brain injury both lactate release and glucose uptake were reduced and there was a net lactate influx at high arterial lactate levels. These results indicate that the flux of lactate in and out of the brain is not only dependent on the lactate concentration in the brain, but on blood levels as well, possibly because of bi-directional flux through the monocarboxylate transporter type 1.

A versatile biosensor device for continuous biomedical monitoring

Although biosensors are by means suitable for continuous biomedical monitoring, due to fouling and blood clotting, in vivo performance is far from optimal. For this reason, ultrafiltration, microdialysis or open tubular flow is frequently used as interface. To secure quantitative recoveries of the analyte of interest, sampling at submicrolitre level will be necessary which in turn necessitates the development of small and versatile biosensor devices. Here, a miniaturised biosensor device, which directly can be connected to various interfaces will be presented. The biosensor device consists of a pulsefree pump and a biosensor with an internal volume of 10-20 nl. In this article, the production as well as the construction of the flow-through cell of the biosensor will be discussed. The advantages and disadvantages of several production processes will be demonstrated and a detailed protocol for the production of such a nanoliter flow-through cell will be presented. With respect to the bio-selector, several permselective membranes have been tested on their performance characteristics. Results obtained with these biosensors will be presented and discussed. Finally, a protocol based upon in situ electropolymerisation for the immobilisation of the biological component was defined and several biosensors based upon this principle have been produced and tested for the monitoring of glucose respectively lactate. To demonstrate, data obtained during a variety of in vivo studies at different clinical relevant applications will be presented.

On-line continuous monitoring of glucose or lactate by ultraslow microdialysis combined with a flow-through nanoliter biosensor based on poly(m-phenylenediamine) ultra-thin polymer membrane as enzyme electrode

A miniaturised flow-through biosensor with a cell volume of only a few nanoliters was developed in our laboratory. The biosensor can be directly coupled to a microdialysis or ultrafiltration probe. Sampling and continuous on-line monitoring can thus be carried out at submicroliter levels and as a consequence quantitative recoveries of the analyte of interest are achieved. Via this method excessive calibration procedures, as are necessary with conventional microdialysis, are avoided. Here, the construction and the performance of such a biosensor for the continuous on-line monitoring of glucose and lactate will be presented. The biosensor is based on the amperometric detection of hydrogen peroxide after conversion of the analyte of interest by an immobilised oxidoreductase enzyme. Immobilisation of the enzyme is performed through electropolymerisation of m-phenylenediamine. Strategies to improve the performance (e.g. linearity, selectivity and stability) of the miniaturised biosensor are discussed and ex vivo and in vivo experiments carried out thus far demonstrate the potential of this miniaturised flow-through biosensor.

An ultrafiltration catheter for monitoring of venous lactate and glucose around myocardial ischemia

Early detection of myocardial ischemia is of major importance in critical-care medicine. Changes of lactate or glucose levels in the cardial venous efflux may be useful parameters. We succeeded in integrating an ultrafiltration membrane in a cardiac catheter for continuous sampling. The ultrafiltrate was analyzed outside the body, resulting in a lag-time of about 24 min. Biosensors in a flow-injection analysis system were used for minute by minute sample analyses. The coronary sinus of pigs was catheterized to monitor the effects of 5, 15 or 45 min ischemia by coronary artery obstruction or myocardial stress by dobutamine infusion. A total of 27 h was monitored. The intravascular response time was 1.33+/-0.61 min (10-90%). Linear regression in vivo of blood and ultrafiltrate samples was 0.977 for lactate and 0.994 for glucose. Lactate levels rose 0.38+/-0.10 mM above baseline within 5 min after ischemia. Reperfusion was clearly marked by a promptly peaking lactate release (maximum 9.27 mM). Myocardial stress by dobutamine increased glucose but not lactate levels. Once, a wall effect was noted at the catheter tip. In vivo semi-continuous myocardial monitoring of absolute lactate and glucose concentrations was thus achieved by an ultrafiltration catheter. Ischemia and reperfusion can be detected very early by a lactate level rise. Further, development of the ultrafiltration catheter will be focused on the diagnostic potential of lactate monitoring for patients.