Short-chain Organic Acids Research Articles

The main generation stage of organic acids during source-rock maturation: Implications for reservoir alteration in deep strata

Generation of short-chain organic acids during source rock maturation was simulated over 72 h, using different kerogens at 220°C–360°C. A Youganwo Formation Type I kerogen sample had the highest organic acid yield (31.0 mg g−1 total organic carbon), twice that of the Yanchang and Kezilenuer formation samples (Type II and III kerogens, ∼15 mg g−1). The organic acids were generated mainly in the oil window, regardless of kerogen type. Type I and II kerogen-bearing source rocks produced organic acids with an equivalent vitrinite reflectance (EasyRo) of 1.16%, slightly later than the peak generation of liquid hydrocarbons. Type III kerogen-bearing source rocks produced acids at an early stage (0.95% EasyRo). Most organic acids dissolved in pore waters might have been expelled with hydrocarbons from source rocks containing type I and II kerogen, migrating to reservoirs. Pores and cavities in reservoirs along faults and conduits or near source rocks could be enlarged by mineral dissolution caused by organic acids, with the generated pore space being occupied by the migrated hydrocarbons. During continued burial, these porosities would be preserved, even in deep reservoirs.

Plant pathological condition is associated with fungal community succession triggered by root exudates in the plant-soil system

Root-associated microbiota is important for plant health, but there is limited knowledge of how plant pathological condition influences the succession of soil microbial communities, especially the fungal community, in plant-soil systems. We investigated the fungal community succession across a gradient from bulk soil to the plant endosphere of diseased and healthy lisianthus plants using quantitative real-time PCR, amplicon sequencing, and metabolomics. Fungal diversity and richness gradually decreased from the bulk soil to root endosphere, and there were fewer fungi in the rhizosphere soil of diseased plants than healthy plants. While the rhizosphere fungal communities developed to be similar with that of the endosphere in both diseased and healthy plants from flowering to harvesting, the rhizosphere fungal community developed more quickly in diseased plants than healthy plants. More potential antifungal members were present in the bulk soil and rhizosphere of healthy plants, while potential pathogens were more prevalent in the diseased samples. There were significantly more F. oxysporum in the rhizosphere than the bulk soil, and the enrichment of F. oxysporum (i.e. Fusarium wilt pathogen) occurred more quickly in the rhizosphere of diseased plants than healthy plants. More importantly, the root relative electrical conductivity, the concentration of secreted short-chain organic acids like succinic and malic acids, and sugar alcohols were greater in diseased plants than healthy plants. These changes in plant physiology were associated with the faster development of the fungal community and more rapid increase in the pathogen population in the diseased rhizosphere. Taken together, our results highlight the importance of plant pathological condition for the assembly and development of fungal communities in plant-soil systems.

Characteristics of bacterial and yeast microbiomes in spontaneous and mixed-fermentation beer and cider

The production of experimental beer and cider products has increased, worldwide. The complex microbiomes found in these beverages affect their organoleptic qualities and chemical compositions and can have diverse impacts on human health. The total diversity of a microbiome can be elucidated through the use of high-throughput sequencing and comprehensive data analysis tools.We analysed the bacterial and yeast microbiomes found in mixed and spontaneously fermented beers (n = 14) and unpasteurised apple ciders (n = 6), using high-throughput 16S rRNA and internal transcribed spacer (ITS) sequencing. The ratio of bacteria to yeast was measured using quantitative polymerase chain reaction (qPCR), and short-chain organic acids were analysed using high-performance liquid chromatography (HPLC). An upgraded version of the Knomics-Biota system was used to analyse the data.The microbiomes included both starter microorganisms and those that originate from the production environment and the raw materials. In addition to the common Saccharomyces and Brettanomyces, the yeast diversity included many non-conventional species. The bacterial community in beer was dominated by Lactobacillus species, whereas these communities were more diverse in cider. Lactobacillus acetotolerans was prevalent in wild ales, whereas Candida ethanolica was prevalent in cask-matured beverages. We observed complex patterns of subspecies-level yeast diversity across beer styles, breweries, and countries.Our study represents an exploratory analysis of non-conventional beer and cider microbiomes and metabolomes, which contributes information necessary to develop improved quality control processes and may drive innovative product development in experimental and artisanal brewing.

Current advance in biological production of short-chain organic acid.

As natural metabolites, organic acids have been widely applied in food, pharmaceutical, and bio-based materials industries. Particularly, the short-chain organic acids, including C2, C3, C4, C5, and C6 organic acids, are necessary intermediate metabolites in cells and are also alternatives to some commercial chemical products. As the necessary metabolites in cells, most major short-chain organic acids can be produced through microbial fermentation. Specifically, with the development of synthetic biology, metabolic engineering could endow cells with the ability to produce more short-chain organic acid products including propionic acid, pyruvate, lactic acid, 3-hydroxypropionic acid, malic acid, succinic acid, fumaric acid, butyric acid, itaconic acid, α-ketoglutaric acid, glutaric acid, citric acid, gluconic acid, muconic acid, adipic acid, xylonic acid, and so on. The recent advances in the biological production of short-chain organic acids, as well as the challenges and perspectives, are summarized in this review to promote the generation of microbial cell factories for the production of short-chain organic acids.Key points• Outlines the production strategy of short-chain organic acids• Provide guidance for efficient synthesis of short-chain organic acids• Impacts the necessary factor of acid resistance on the successful production of host cells.

Metabolite profiling of mice under long-term fructose drinking and vitamin D deficiency: increased risks for metabolic syndrome and nonalcoholic fatty liver disease.

Chronic fructose consumption and vitamin D deficiency (VDD) diet have been linked to the pandemic of metabolic syndrome (MetS) and nonalcoholic fatty liver disease (NAFLD). The metabolic mechanisms remain unclear. This study is to explore metabolic changes of mice fed with high fructose syrup and VDD diet in the biogenesis of MetS and NAFLD. C57BL/6J mice were treated with four conditions for 28weeks: control (standard chow and sterile water), fructose drinking (FD, standard chow and 20g/100mL fructose in drinking water), VDD (standard chow with VD depleted and sterile water), and FD+VDD. Metabolites in the serum and liver of mice were analyzed by gas chromatography-mass spectrometry combined with trimethylsilyl derivatization. The histological results indicated that one-hit from long-term fructose drinking led to mild MetS, and a combination with VDD diet induced hepatic steatosis, inflammatory lesion, and interstitial fibrosis in mice, showing significant nonalcoholic steatohepatitis features. Metabolomics analysis showed significant changes in amino acids and short-chain organic acids in response to fructose drinking. VDD diet led to significant increase of hepatic fatty acids, which was consistent with the hepatic morphology of fat deposition. This work demonstrated a concert effect of FD and VDD in promoting MetS and NAFLD through changing in vivo metabolism and signaling pathways. And metabolomics analysis could provide early warnings for the biogenesis of MetS and NAFLD. Importantly, vitamin D supplementation in the diet can balance the metabolic disorders caused by excessive fructose intake.

Effect of the operating conditions on the anaerobic digestion of wheatgrass for chemicals and energy production

The aim of this study was to investigate anaerobic digestion of wheatgrass in the absence of hydrolytic pre-treatments. The effect of solids retention time (SRT) (1–64 days), inoculum acclimation (0–80 days acclimation), temperature (40–70 °C) and buffer capacity (20–200 mM phosphate buffer) on conversion of the feedstock, yield and composition of liquid-phase products (ethanol and short-chain organic acids, SCOAs) and COD removal was investigated in semi-continuous (intermittent feed) completely mixed reactors. SRT had the most important effect on process performance. Biodegradation of the feedstock was favoured at high SRT, with 61% removal of volatile suspended solids and 84% removal of total carbohydrates at SRT 64 days. However, low yield of liquid-phase products was observed at high SRT because of strong methanogenic activity (57% removal of the total COD). The highest yield of liquid-phase products was 20% (COD basis) at SRT 8 days. Although high biodegradation of the feedstock was observed after long-term batch acclimation (30 and 80 days), once the digestion conditions were switched to semi-continuous at short SRT (2 days), the biodegradation of the feedstock decreased considerably. The best process performance was observed at 40 °C.

Chemical composition of thermally processed coconut water evaluated by GC–MS, UPLC-HRMS, and NMR

Thermally-processed coconut water often develop a commercially-undesirable pink color, thus, NMR, UPLC-HRMS, GC–MS analyses combined with chemometrics approach were applied to evaluate chemical variations in comparison to tender water (control) that could explain such color change. Chemometrics on negative ionization mode dataset showed trimeric and A-type dimeric procyanidins, and caffeoylshikimic acid as main identified secondary metabolites induced by processing, while, control water presented mainly cytokinin trans-zeatin riboside, procyanidin dimer, caffeoylshikimic acid and trihydroxy-octadecenoic acid. Processing increased long-chain saturated palmitic and stearic fatty acids contents, meanwhile NMR analysis showed a decline in primary metabolites content as sugars fructose and glucose, and short-chain organic acids. Among the results observed for thermally processed coconut water, the increase in oligomeric procyanidins as A-type dimer and trimer may be associated with pink color development as these are precursors of anthocyanin pigment and/or by enhancing color stability of anthocyanin solutions.

Negative retention by the nanofiltration of aqueous biomass hydrolysates derived from wood pulping

Separation of sugars and aldonic acids from aromatic compounds and short-chain organic acids is a crucial issue in various biorefinery concepts based on wood or agricultural byproducts, which can be resolved by nanofiltration. Model solutions containing up to six compounds, representing major components of biomass hydrolysates, were used to investigate interactions between the individual chemical species, with particular emphasis on the negative retention of 5-hydroxymethylfurfural (HMF) and acetic acid (AcOH).Various factors were found to explain the negative retention of these substances in binary and multicomponent mixtures. The presence of gluconic acid led to the negative retention of AcOH due to an additional electric potential. For HMF retention, the hydration shell formed during the solvation of magnesium sulfate was determined as the main influencing factor. For the first time, the obtained results provide a mechanistic explanation for the negative retention of biomass hydrolysates. In addition, a novel methodology based on a revised concept of retention to quantitatively describe such effects in binary mixtures is provided, which can be qualitatively applied to any biomass hydrolysate. Our results are expected to make nanofiltration for the separation of biomass hydrolysates more predictable, thereby facilitating process development.

Strong pH dependence of hydrogen production from glucose by Rhodobacter sphaeroides

Purple non-sulfur bacteria (PNSB) are well known for converting short-chain organic acids to H2, however, a decrease in pH caused by metabolic acids production limited H2 production during the photo-fermentation from glucose. Here we address why volatile fatty acids (VFA) excreted as fermentation products cannot be further degraded by R. sphaeroides that readily use them. We found that the photo-fermentation with pH controlled at 6.9 ± 0.1 resulted in a 90% increase of H2 yield and a 107.6% increase in volume H2 production relative to the pH-uncontrolled culture. Comparative fermentations on glucose at pH 5.8 and pH 7.1 using culture medium supplemented with 50% spent fermentation broth demonstrated that low pH alone is not the limiting factor and compounds present in the supernatants along with pH decrease were the most inhibitory to H2 production. The impact of byproducts VFA on phototrophic H2 production was dependent on both the pH and VFA concentrations; even 7 mM VFA addition totally inhibited H2 production from glucose at pH 5.4. H2 production with pH control for the Δhup strain was not discernibly different from the parent strain, which are all significantly higher than high-performance strains by metabolic engineering. These results demonstrate that pH dependent VFA inhibition can be turned into a driving force for enhanced H2 production from glucose by pH regulation.

Dispersive liquid–liquid microextraction method for the extraction of acidic pesticides in edible oils; application of short-chain organic acids as co–disperser and protonation agent

ABSTRACT In the present study, a sample pretreatment based on the combination of vortex assisted liquid–liquid extraction and dispersive liquid–liquid microextraction has been proposed for the isolation and preconcentration of three acidic herbicides including fenoxaprop, fluazifop, and haloxyfop from edible oil samples. For this purpose, firstly, the analytes were extracted into sodium hydroxide solution (by deprotonating the analytes) which was used as a dispersive solvent in the following microextraction procedure. The obtained aqueous phase was mixed with acetic acid as a pH adjustment agent and co–disperser solvent. After the addition of dichloromethane (extraction solvent) to the above solution, it was quickly dispersed into deionised water. The validation parameters indicated that the limits of detection and quantification of the proposed method were in the ranges of 0.3–1.8 and 1.0–6.0 ng mL–1, respectively. Relative standard deviations of the method were obtained in the range of 4.8–6.2% and 5.2–9.1% for intra – (n = 6) and inter–day (n = 5) precisions, respectively. High extraction recoveries and enrichment factors ranged from 74 to 91%, and 185 to 227 were the other advantages of the method. These merits showed that the proposed method is efficient and sensitive for the determination of the studied analytes in the edible oil samples.

Effects of Medium Chain Fatty Acids on Intestinal Health of Monogastric Animals.

Medium-chain fatty acids (MCFAs) are the main form of Medium Chain Triglycerides (MCTs) utilized by monogastric animals. MCFAs can be directly absorbed and supply rapid energy to promote the renewal and repair of intestinal epithelial cells, maintain the integrity of intestinal mucosal barrier function, and reduce inflammation and stress. In our review, we pay more attention to the role of MCFAs on intestinal microbiota and mucosa immunity to explore MCFA's positive effect. It was found that MCFAs and their esterified forms can decrease pathogens while increasing probiotics. In addition, being recognized via specific receptors, MCFAs are capable of alleviating inflammation to a certain extent by regulating inflammation and immune-related pathways. MCFAs may also have a certain value to relieve intestinal allergy and inflammatory bowel disease (IBD). Unknown mechanism of various MCFA characteristics still causes dilemmas in the application, thus MCFAs are used generally in limited dosages and combined with short-chain organic acids (SOAs) to attain ideal results. We hope that further studies will provide guidance for the practical use of MCFAs in animal feed.

Effect of the process conditions on the anaerobic fermentation of glucose for the production of chemicals

In the context of biorefinery for the production of chemicals, this study optimised the processes to enhance the anaerobic production of ethanol and short-chain organic acids from glucose. The optimised variables included (with a total of 49 runs) residence time (2–100 h), temperature (25–35 °C), type of inoculum (soil or anaerobic digester), presence or absence of pre-acclimation of the inoculum, glucose concentration (5–50 g/L), continuous or batch mode and composition of the mineral media (mineral solution with or without trace elements, with deionised or tap water). In continuous experiments, the residence time was the most important parameter that affected glucose conversion (over 80% glucose conversion for residence time longer than 30 h) and product yields (ethanol was the main product in the range of residence times 20–50 h, with yields in the range 0.30–0.40 g/g glucose removed). Temperature, type of inoculum, and pre-acclimation had little effect on glucose conversion and products yield. The addition of trace elements had an important beneficial effect on the removal of glucose when it was fed at the highest concentration (50 g/L) in both continuous and batch experiments. In batch runs, acetate was generally the main fermentation product rather than ethanol and ethanol conversion into acetate was favoured by nitrogen sparging, probably due to the reduced hydrogen partial pressure.

Graphene as efficient and robust catalysts for catalytic wet peroxide oxidation of phenol in a continuous fixed-bed reactor

Monolayer graphene film (Gr) as a metal-free catalyst was synthesized on the paper-like sintered stainless steel fibers (PSSF) with three-dimensional net structure by chemical vapor deposition (CVD) technique. The prepared PSSF-Gr was characterized by SEM, EDS, XRD, AFM, TEM, and Raman spectroscopy. Then, the optimum reaction conditions for catalytic wet peroxide oxidation (CWPO) of phenol in a continuous reactor using PSSF-Gr catalysts were explored by analyzing the effects of reaction temperature, feed flow rate, and catalyst bed height on catalytic performance. Moreover, the long-term stability of PSSF-Gr catalyst was investigated and demonstrated complete phenol oxidation and dramatic TOC removal (values ranging between 80.7% and 91.0%) after continuously operating for 72 h under optimum condition. Finally, a reasonable reaction mechanism for CWPO of phenol was proposed by analyzing the HPLC results and evolution of aromatic intermediates content. From these results, seldom toxic aromatic intermediates were observed on account of the production of short-chain organic acids by opening of aromatic ring, which subsequently mineralized to CO2 and H2O. The simple preparation method, unique structure, extraordinary catalytic activity and stability of the graphene-based material would provide a new potential catalyst for environmental catalysis.

Identification of major malate export systems in an engineered malate-producing Escherichia coli aided by substrate similarity search

Optimization of export mechanisms for valuable extracellular products is important for the development of efficient microbial production processes. Identification of the relevant export mechanism is the prerequisite step for product export optimization. In this work, we identified transporters involved in malate export in an engineered L-malate-producing Escherichia coli strain using cheminformatics-guided genetics tests. Among all short-chain di- or tricarboxylates with known transporters in E. coli, citrate, tartrate, and succinate are most chemically similar to malate as estimated by their molecular signatures. Inactivation of three previously reported transporters for succinate, tartrate, and citrate, DcuA, TtdT, and CitT, respectively, dramatically decreased malate production and fermentative growth, suggesting that these transporters have substrate promiscuity for different short-chain organic acids and constitute the major malate export system in E. coli. Malate export deficiency led to an increase in cell sizes and accumulation of intracellular metabolites related to malate metabolism.

Application of vacuum-ultraviolet (VUV) for phenolic homologues removal in humic acid solution: Efficiency, pathway and DFT calculation

Vacuum-ultraviolet (VUV) photo-initiated oxidation of phenolic homologues in simulative natural water were investigated, including phenol, o-dihydroxybenzene (ODB), m-dihydroxybenzene (MDB), p-dihydroxybenzene (PDB), paranitrophenol (PNP) and o-chlorophenol (OCP). Results showed the phenolic homologues removal rate reached at least 90% in pure water, which was dependent on temperature, pH, concentration of HA, and functional group of HA. Experimental results indicated that 0.2 mg/L HA might be a critical point. Additionally, the rate constant of the six phenolic homologues reduced by 76.85%, 77.81%, 71.91%, 79.15%, and 55.69%, respectively in the MDB solution, and 79.73%, 82.80%, 95.36%, 80.38%, and 92.64%, respectively in the benzoic acid (BA) solution, compared to the rate constant in pure water. Moreover, quantum chemistry calculation indicated that the variances between phenolic compounds in removal rate were attributed to the substituent on the benzene ring. And, to some extent, the carboxy group of HA was supposed to arose the suppression for phenolic homologues removal rate. Mechanism involved phenolic homologues degradation using vacuum-ultraviolet (VUV) was summarized, where it underwent the formation of quinone structures, ring opening, short-chain organic acid, even eventually the transformation into NO3− and Cl− of PNP and OCP.

Origin of Short-Chain Organic Acids in Serpentinite Mud Volcanoes of the Mariana Convergent Margin.

Serpentinitic systems are potential habitats for microbial life due to frequently high concentrations of microbial energy substrates, such as hydrogen (H2), methane (CH4), and short-chain organic acids (SCOAs). Yet, many serpentinitic systems are also physiologically challenging environments due to highly alkaline conditions (pH > 10) and elevated temperatures (>80°C). To elucidate the possibility of microbial life in deep serpentinitic crustal environments, International Ocean Discovery Program (IODP) Expedition 366 drilled into the Yinazao, Fantangisña, and Asùt Tesoru serpentinite mud volcanoes on the Mariana Forearc. These mud volcanoes differ in temperature (80, 150, 250°C, respectively) of the underlying subducting slab, and in the porewater pH (11.0, 11.2, 12.5, respectively) of the serpentinite mud. Increases in formate and acetate concentrations across the three mud volcanoes, which are positively correlated with temperature in the subducting slab and coincide with strong increases in H2 concentrations, indicate a serpentinization-related origin. Thermodynamic calculations suggest that formate is produced by equilibrium reactions with dissolved inorganic carbon (DIC) + H2, and that equilibration continues during fluid ascent at temperatures below 80°C. By contrast, the mechanism(s) of acetate production are not clear. Besides formate, acetate, and H2 data, we present concentrations of other SCOAs, methane, carbon monoxide, and sulfate, δ13C-data on bulk carbon pools, and microbial cell counts. Even though calculations indicate a wide range of microbial catabolic reactions to be thermodynamically favorable, concentration profiles of potential energy substrates, and very low cell numbers suggest that microbial life is scarce or absent. We discuss the potential roles of temperature, pH, pressure, and dispersal in limiting the occurrence of microbial life in deep serpentinitic environments.

Comparison of Uranium Extraction by Bio-product of 3 Bacteria Strains Isolated from Shihongtan Uranium Deposite, Xinjiang, China

It is well known that bacteria produce short-chain organic acids and element-specific ligands (siderophores) that are able to change pH and enhance chelation, which results in increased mobilization of uranium. This research work represents the extraction of Uranium by Siderophores (bio-products) producing microbial species Myroides Odoratimimus, Pseudomonas Aeruginosa, and Pseudomonas Fluorescens were incubated in a chemically defined medium supplemented with uranium ore. Batch leaching tests were performed in neutral conditions for 7 days. With Myroides Odoratimimus, uranium was leached out in test about 20 mg/L, with Pseudomonas Aeruginosa, it was about 12 mg/L and with Pseudomonas Fluorescens it was about 10 mg/L. Uranium extraction with Myroides odoratimimus was higher as compared to others was due to the production of greater siderophores as compared to the other two strains. This comparative study showed that the strain produced greater siderophores production leached out more uranium as compared to other strains. For future suggestions, better siderophores producing bacterial strains may be used at an industrial scale to extract heavy metals like uranium.

Evaluation of Anti-Inflammatory Properties of Herbal Aqueous Extracts and Their Chemical Characterization.

Plant extracts are gaining more attention as therapeutic agents against inflammation. In this study, four different widely used herbals were selected, such as holy basil leaf, sesame seed, long pepper, and cubeb pepper. We have evaluated the anti-inflammatory action of an aqueous extract from these herbs and tested their effects on monocyte-derived macrophages (MDMs). MDMs were pre-treated with these extracts individually for 2 h, followed by lipopolysaccharide (LPS) stimulation for 24 h and pro-inflammatory gene expression was analyzed. Also, we studied the effect of these extracts on the oxidation of low-density lipoprotein (LDL) by enzymatic (Myeloperoxidase) and non-enzymatic (copper) reactions. All extracts attenuated LPS-induced inflammation and also were able to inhibit the oxidation of LDL. These beneficial actions of extracts led us to identify molecules present in the extracts. A liquid chromatography-high resolution mass spectrometric analysis was performed to identify the chemical composition of extracts. Wide range of molecules were identified across all the extracts, short-chain organic acids, phenolic acids and derivatives, piperine and its structural homologues, eugenol, rosmarinic acid, flavonoids and their glucosides, and others. This study opens a door for future studies on non-pharmacological natural therapeutics that will be useful for consumers and producers, as well as industries utilizing bioactive compounds.

Valorising fermentation effluent rich in short-chain fatty acids and sugars for biohydrogen via photofermentation by Rhodobacter sphaeroides KKU-PS1

Growing fermentative chemical production will increase effluents from industrial fermentations containing short-chain fatty acids and residual sugars, which are exploitable for biohydrogen through photofermentation. Previous studies have concentrated on single substrates and photofermentation study using fermentation effluent from bio-succinate production containing residual sugars and short-chain organic acids has yet to be reported to the best of authors’ knowledge. Rhodobacter sphaeroides KKU-PS1 grown on succinate was used for hydrogen production from medium containing mixture of substrates mimicking final effluent from bio-based succinate production. Prior to that, hydrogen producibility test with succinate-only medium was carried out. Photofermentation from succinate by this strain yielded 1217 ml H2/l of maximum cumulative hydrogen with maximum hydrogen rate of 6.7 ml H2/l/h, comparable to malate which was previously reported as best single substrate for the strain. Hydrogen production profiles using mixed substrates was well-fitted by modified Gompertz model with maximum cumulative hydrogen and maximum hydrogen production rate of 1005 ml H2/l and 4.1 ml H2/l/h, respectively. Only glucose, xylose and succinate followed modified Gompertz model for substrate consumption. Instantaneous succinate consumption compared to extended lag time of 100h for consumption of both sugars indicated higher affinity towards short-chain fatty acid utilization during initial growth phase. Xylose showed highest overall substrate consumption signifying its importance for hydrogen generation, which continued after stationary growth phase started reaching a total of 91.9% consumption. Significant remaining substrate levels other than xylose suggested that the process was not inhibited by limited substrates. The study highlighted potential of fermentation effluents containing mixed substrates for biohydrogen, with further optimization needed.

Comparing the Ileal and Hindgut Fermentations in the Pig Model (P08-087-19)

ObjectivesThis study aimed to compare ileal and hindgut fermentations in the pig model using a combined in vivo/in vitro methodology. MethodsPigs (23 kg bodyweight, n = 5) were fed a human-type diet for 15 days. On day 15, pigs were euthanased and the small intestine was immediately dissected out and ligated in three equal lengths. Digesta from the last 50 cm of the second (terminal jejunum) and last (terminal ileum) third sections of the small intestine were collected as substrates. Digesta from the remaining last third (i.e., last third minus 50 cm) of the small intestine (ileum) was collected along with caecal digesta for preparing inocula. Terminal jejunal digesta substrates were fermented in vitro with a pooled ileal digesta inoculum for 2 h (ileal fermentation), while terminal ileal digesta substrates were fermented in vitro with a pooled caecal digesta inoculum for 24 h (hindgut fermentation). ResultsThe ileal organic matter (OM) fermentability (28%) was similar than the hindgut counterpart (35%) (P > 0.05). However, the fermentable OM was 63% higher during ileal fermentation than hindgut fermentation (P < 0.05). The production of acetic, isovaleric and succinic acids was higher during ileal fermentation than caecal fermentation (P < 0.05), but the production of propionic, iso-butyric, butyric, valeric and pyruvic acids was lower (P < 0.05). The SCFAs produced in each gastrointestinal tract location was absorbed in their respective gastrointestinal tract location. ConclusionsAn important amount of OM is fermented in the ileum producing comparable amounts of short-chain fatty acids and organic acids to hindgut fermentation. This challenge the current paradigm concerning gastrointestinal tract fermentation. Funding SourcesCentre of Research Excellence Fund from the Tertiary Education.