Short-chain Volatile Fatty Acids Research Articles

Chain elongation may occur in protein mixed-culture fermentation without supplementing electron donor compounds

This study focuses on verifying the occurrence of elongation processes during protein mixed culture fermentation, without the supplementation of electron donor compounds. During casein mixed-culture fermentation at pH 5, it was observed that longer chain volatile fatty acid production increased, which could not be justified by the associated amino acid consumption. Consequently, the occurrence of chain elongation processes was hypothesized. To verify this hypothesis, three casein batch tests, with and without acetic acid initial supplementation, were performed at pH 5. The results suggest that acetic and propionic acids are indeed consumed to selectively generate n-valeric acid through the coupling with electron donor amino acids, whose consumption was further verified through the amino acid analysis. Prolonged simultaneous availability of suitable amino acids and short chain volatile fatty acids and an acid equivalent concentration threshold were identified as key parameters for the occurrence of chain elongation. The supplementation of acetic acid at the beginning of the test changed the selectivity of the elongation process, promoting n-butyric and iso-valeric production. The associated mechanisms were preliminary conceptualized, constituting a first step for further studies on the subject. To the best of our knowledge, this is the first study demonstrating the feasibility of chain elongation processes during protein mixed culture fermentation without electron donor supplementation.

Dietary Enteromorpha Polysaccharide Enhances Intestinal Immune Response, Integrity, and Caecal Microbial Activity of Broiler Chickens.

Marine algae polysaccharides have been shown to regulate various biological activities, such as immune modulation, antioxidant, antidiabetic, and hypolipidemic. However, litter is known about the interaction of these polysaccharides with the gut microbiota. This study aimed to evaluate the effects of marine algae Enteromorpha (Ulva) prolifera polysaccharide (EP) supplementation on growth performance, immune response, and caecal microbiota of broiler chickens. A total of 200 1-day-old Ross-308 broiler chickens were randomly divided into two treatment groups with ten replications of ten chickens in each replication. The dietary treatments consisted of the control group (fed basal diet), and EP group (received diet supplemented with 400 mg EP/kg diet). Results showed that chickens fed EP exhibited significantly higher (P < 0.05) body weight and average daily gain than the chicken-fed basal diet. In addition, significantly longer villus height, shorter crypt depth, and higher villus height to crypt depth ratio were observed in the jejunal and ileal tissues of chickens fed EP. EP supplementation upregulated the mRNA expression of NF-κB, TLR4, MyD88, IL-2, IFN-α, and IL-1β in the ileal and jejunal tissues (P < 0.05). Besides, we observed significantly higher (P < 0.05) short-chain volatile fatty acids (SCFAs) levels in the caecal contents of the EP group than in the control group. Furthermore, 16S-rRNA analysis revealed that EP supplementation altered gut microbiota and caused an abundance shift at the phylum and genus level in broiler chicken. Interestingly, we observed an association between microbiota and SCFAs production. Overall, this study demonstrated that supplementation of diet with EP promotes growth performance, improves intestinal immune response and integrity, and modulates the caecal microbiota of broiler chickens. This study highlighted the application of marine algae polysaccharides as an antibiotic alternative for chickens. Furthermore, it provides insight to develop marine algae polysaccharide-based functional food and therapeutic agent.

Accelerating anaerobic hydrolysis acidification of dairy wastewater in integrated floating-film and activated sludge (IFFAS) by using zero-valent iron (ZVI) composite carriers

Flocculent sludge system usually shows a low treatment efficiency and bad resistance to the feeding shock in the hydrolysis acidification. Integrated floating-film and activated sludge (IFFAS) is a favored system to resist shock, and zero-valent iron (ZVI) is an attractive material to enhance hydrolysis acidification. In this study, an IFFAS equipped with ZVI composite carriers was used to stably increase the degree of acidification (DA) in the anaerobic treatment of dairy wastewater. At the influent organic loading rate of 24.0 kg COD/m3/d with the hydraulic retention time of 3 h, the DA in the reactor filled with ZVI composite carriers was as high as 51.6%, which increased by 9.5% and 7.7%, respectively, comparing with the reactor without biofilm carriers and the reactor filled with polyethylene biofilm carriers. Also, the ZVI composite carriers optimized the biofilm formation and enhanced the activity of protease, pyruvate oxidoreductase, and acetate kinase. Microbial community analysis revealed that hydrolysis acidification bacteria of Comamonas (47.0%) and Petrimonas (2.6%), and acetotrophic methanogens of Methanosarcina (47.1%) and Methanothrix (16.0%) were enriched in the biofilm of ZVI composite carriers. Apart from the main enhancement of mediated interspecies electron transfer, a potential direct interspecies electron transfer also might be established for the presence of Comamonas, Petrimonas, Methanosarcina, and Methanothrix, accelerating the syntrophic production of short-chain volatile fatty acids and methane.

Optimization of short chain volatile fatty acids production from household food waste for biorefinery applications

Household Food Wastes (HFW) are the most abundant organic wastes at urban level with a worldwide annual production of about 2 billion tons. This material can be the right feedstock for a carboxylate biorefinery platform. This work investigated the influence of different operational parameters (pH, temperature, Organic Loading Rate) on the Volatile Fatty Acids production and on their composition. It was demonstrated that, keeping constant the fermentation duration at 6 days, neutral pH, thermophilic temperature (55 °C) and an organic loading rate of 11 gTVS per Liter per day maximized the VFA production with a yield of 0.38 gVFA per gTVS fed. Under these conditions, the main VFAs were butyric and caproic acids with percentages around 60 and 20%, respectively.3. The analysis of the mixed microbial community performed over the reactor operation showed the dominance of members of Firmicutes phylum mainly affiliated to Clostridium and Lactobacillus genera. The process was mostly driven by Clostridium species in mesophilic runs characterized by stable VFAs production and highest yields whereas Lactobacillus was enriched under thermophilic operating conditions. • Household Food Wastes (HFW) is the most abundant waste stream in urban context. • HFW were used for the Volatile Fatty Acids production (VFAs) by dark fermentation. • Different operational parameters were investigated on the VFAs production. • Neutral pH, thermophilic temperature and an OLR of 11 gTS/Ld optimized the VFA amount. • The influence of different parameters on the microorganisms community was studied.

Pushing the organic loading rate in electrochemically assisted anaerobic digestion of blackwater at ambient temperature: Insights into microbial community dynamics

Decentralized blackwater treatment by anaerobic digestion is being considered as a sustainable sanitation concept. However, the low biodegradability and complex composition restrictedly limited the treatability of blackwater, resulting in requirements of low operational organic loading rates (OLRs). In this study, a microbial electrolysis cell assisted anaerobic digester (MEC-AD) treating vacuum toilet blackwater was successfully operated for 420 days at OLRs ranging from 0.77 to 3.03 g COD/L-d in 6 stages (including an open-circuit Stage 5) at ambient temperature. Based on the steady-state results from different stages, the highest methane yield (42.4% out of 45% biochemical methane potential value) was achieved in Stage 1 with an OLR of 0.77 g COD/L-d. At the same OLR of ~3.0 g COD/L-d, Stage 4 (32.4%) and Stage 6 (35.2%) showed significantly higher methane yield (p < 0.01) than open-circuit Stage 5 (24.1%). The lowest COD removal efficiency of 31.8% was observed in Stage 5 with short-chain volatile fatty acids (SCVFAs) accumulated to ~1000 mg/L, which was more than double the values of Stage 4 and 6. The microbial community analysis revealed that the applied potential did not significantly affect archaeal diversity but largely increased the archaeal abundance on the cathode, and led the bacterial community shift with the enrichment of specific electroactive bacteria. Microbial co-occurrence network analysis further confirmed the positive correlations between known electroactive bacteria and electrotrophic methanogens. Moreover, electric energy consumed by the MEC-AD system was fully recovered as biomethane.

High sucrose diet-induced dysbiosis of gut microbiota promotes fatty liver and hyperlipidemia in rats

Excess sucrose intake has been found to be a major factor in the development of metabolic syndrome, especially in promoting nonalcoholic fatty liver disease. The excess fructose is believed to targets the liver to promote de novo lipogenesis, as described in major biochemistry textbooks. On the contrary, in this study, we explored the possible involvement of gut microbiota in excess sucrose-induced lipid metabolic disorders, to validate a novel mechanism by which excess sucrose causes hepatic lipid metabolic disorders via alterations to the gut microbial community structure. Wistar male rats were fed either a control starch diet or a high-sucrose diet for 4 weeks. Half of the rats in each group were treated with an antibiotic cocktail delivered via drinking water for the entire experimental period. After 4 weeks, rats fed with the high-sucrose diet showed symptoms of fatty liver and hyperlipidemia. The architecture of cecal microbiota was altered in rats fed with high-sucrose diet as compared to the control group, with traits including increased ratios of the phyla Bacteroidetes/Firmicutes, reduced α-diversity, and diurnal oscillations changes. Antibiotic administration rescued high-sucrose diet-induced lipid accumulation in the both blood and liver. Levels of two microbial metabolites, formate and butyrate, were reduced in rats fed with the high-sucrose diet. These volatile short-chain fatty acids might be responsible for the sucrose-induced fatty liver and hyperlipidemia. Our results indicate that changes in the gut microbiota induced by a high-sucrose diet would promote the development of nonalcoholic fatty liver disease via its metabolites, such as short-chain fatty acids.

Evaluation of dietary addition of 2 essential oils from Achillea moschata, or their components (bornyl acetate, camphor, and eucalyptol) on invitro ruminal fermentation and microbial community composition.

This study investigated the effects of 2 Achillea moschata essential oils extracted from plants collected in 2 different valleys of the Italian Alps and 3 pure compounds of oils — bornyl acetate (BOR), camphor (CAM), and eucalyptol (EUCA) — on in vitro ruminal fermentation and microbiota. An in vitro batch fermentation experiment (Exp. 1) tested the addition of all of the substances (2 essential oils and 3 compounds) in fermentation bottles (120 mL) at 48 h of incubation, whereas a subsequent in vitro continuous culture experiment (Exp. 2) evaluated the pure compounds added to the fermenters (2 L) for a longer incubation period (9 d). In both experiments, total mixed rations were incubated with the additives, and samples without additives were included as the control (CTR). Each treatment was tested in duplicate and was repeated in 3 and 2 fermentation runs in Exp. 1 and 2, respectively. Gas production (GP) in Exp. 1 was similar for all of the treatments, and short chain volatile fatty acid (SCFA) production was similar in both experiments except for a decrease of SCFA produced (P = 0.029) due to EUCA addition in Exp. 2. Compared to CTR, BOR and CAM reduced the valerate proportion (P = 0.04) in Exp. 1, and increased (P < 0.01) the acetate proportion in Exp. 2. All treatments increased (P < 0.01) total protozoa counts (+36.7% and +48.4% compared to CTR on average for Exp. 1 and 2, respectively). In Exp. 1, all of the treatments lowered the Bacteroidetes and Firmicutes and increased the Proteobacteria relative abundances (P < 0.05), whereas in Exp. 2, the EUCA addition increased (P = 0.012) the Ruminococcus. In Exp. 1, methane (CH4) as a proportion of the GP was lowered (P = 0.004) by the addition of CAM and EUCA compared to CTR, whereas in Exp. 2, EUCA reduced the amount of stoichiometrically calculated CH4 compared to CTR. Overall, essential oils extracted from A. moschata and the pure compounds did not depress in vitro rumen fermentation, except for EUCA in Exp. 2. In both experiments, an increase of the protozoal population occurred for all the additives.

Effect of adding graded levels of lablab forages on fermentation characteristics of Brachiaria silage

Ensiling as a method of forage feed conservation is the most appropriate in conserving of crude protein (CP) enhanced forages for sustainable dairy production. This is attributed to the fact that with this method, protein dependent lactic acid bacteria (LAB) hydrolyze water soluble carbohydrates (WSC) into short chain volatile fatty acids (VFAs) which are precursors for milk synthesis while the proteins buffers the excessive organic acids to produce more acetate and propionate. The study therefore aimed at assessing the quality of Brachiaria silage which was protein supplemented with graded levels of lablab forage. To achieve this objective, wilted Brachiaria forage (Brachiaria hybrid cv Mulato II) was collected, wilted and ensiled with and Lablab purpureus forages at inclusion levels of 0%, 10%, 20%, 30% Lablab purpureus forage. The resultant 4 treatments were assessed in a completely randomized design in 3 replicates. All silages were prepared using plastic jar mini-silos to laboratory scale and then incubated at room temperature (±30°C) for 45 days. After the 45 days, chemical analysis for quantification of water soluble carbohydrate (WSC), none protein nitrogen (NH3-N), Acid detergent fiber (ADF), Neutral detergent fiber (NDF), pH, in-vitro organic matter digestibility (INVOMD), acetic acid, lactic acid and propionic acid composition were conducted. The results indicated that; none protein nitrogen, acetic acid and propionic acid composition decreased in quadratic trends with increasing legume forage inclusion to minimum values of 5.8, 48.0 and 0.7g/kg at 14.7, 1.8 and 6.0% inclusion levels of lablab forage, respectively. On the other hand, following a quadratic trend, WSC composition decreased with increase in lablab forage, with a maximum of 28.9g/kg obtained at 7.6% inclusion level of lablab forage. Generally, CP, dry matter, INVOMD and metabolizable energy of the silage increased with increase in the inclusion levels of lablab silage. Using regression equations of the response curves, NDF and ADF decreased with increasing legume forage inclusion to minimum values of 349.3 and 172.1g/kg at inclusion levels of 16.1 and 17.1%, respectively. On the other hand in-vitro organic matter digestibility increased with the increase in the lablab forage inclusion to a maximum of 49.4%. However, mineral composition of the silage was not affected by lablab forage inclusion. Since the quality of silage for dairy cows depends on short chain volatile fatty acid, fibre and crude protein composition, inclusion of lablab forage to Brachiaria hybrid cv mulato II silage at a rate of 17.1% potentially yields the best results in lactating cows.

Metagenomic analysis reveals a dynamic microbiome with diversified adaptive functions to utilize high lignocellulosic forages in the cattle rumen.

Rumen microbiota play a key role in the digestion and utilization of plant materials by the ruminant species, which have important implications for greenhouse gas emission. Yet, little is known about the key taxa and potential gene functions involved in the digestion process. Here, we performed a genome-centric analysis of rumen microbiota attached to six different lignocellulosic biomasses in rumen-fistulated cattle. Our metagenome sequencing provided novel genomic insights into functional potential of 523 uncultured bacteria and 15 mostly uncultured archaea in the rumen. The assembled genomes belonged mainly to Bacteroidota, Firmicutes, Verrucomicrobiota, and Fibrobacterota and were enriched for genes related to the degradation of lignocellulosic polymers and the fermentation of degraded products into short chain volatile fatty acids. We also found a shift from copiotrophic to oligotrophic taxa during the course of rumen fermentation, potentially important for the digestion of recalcitrant lignocellulosic substrates in the physiochemically complex and varying environment of the rumen. Differential colonization of forages (the incubated lignocellulosic materials) by rumen microbiota suggests that taxonomic and metabolic diversification is an evolutionary adaptation to diverse lignocellulosic substrates constituting a major component of the cattle's diet. Our data also provide novel insights into the key role of unique microbial diversity and associated gene functions in the degradation of recalcitrant lignocellulosic materials in the rumen.

A critical review of microbial electrolysis cells coupled with anaerobic digester for enhanced biomethane recovery from high-strength feedstocks

Anaerobic digestion (AD) is considered as a traditional method for biomethane recovery from high-strength waste and wastewater. The limitations of conventional anaerobic digestion processes include sluggish kinetics, process instability, and low methane yield. Recently, microbial electrolysis cell (MEC) has been demonstrated as a promising approach for enhancing biomethane recovery from various organic feedstocks. In recent years, a variety of hybrid anaerobic bioreactors coupling MEC and AD were employed to improve biomethane recovery and anaerobic treatability of various high-strength feedstocks. The MEC-AD integrated systems also exhibited better process stability than traditional anaerobic digesters by alleviating the accumulation of short-chain volatile fatty acids at higher organic loading rates, as well as mitigating the inhibitory effects of various toxic and refractory compounds. Firstly, this article provides a comprehensive performance review of the MEC-AD systems treating various high-strength (>8 g COD/L) substrates. Secondly, the implications of process parameters, energy efficiencies, and microbial community characteristics are discussed. Finally, valuable operational insights and future research needs are highlighted.

Molecular Modeling and &lt;i&gt;In Vitro&lt;/i&gt; Study of Malodor Inhibition Using Thai Herbal Products

Eighty-one microbial odors were isolated and identified based on phenotypic characterization and 16S rRNA gene sequence similarity. The dominant microbial odors (Group C, 27 isolates) were classified as Staphylococcus hominis subsp. hominis DSM 20328T. The genome annotation of all representative microbial odors revealed that they consisted of malodor biosynthesis pathways; short-chain volatile fatty acids (VFAs) and thioalcohol (3-methyl-3-sulfanyl-hexan-1-ol, 3M3SH). Among them, 3M3SH was the most important malodor compound and its key enzyme was cystathionine beta-lyase. To screen the cystathionine beta-lyase inhibitors by docking with PyRx, three bioactive compounds from natural products [gallic acid (CID 370), 1-heneicosanol (CID 85014) and 2,6-dimethylheptadecane (CID 545603)] were predicted to be effective in binding with the target enzyme close to the synthetic inhibitor [N-(2-Hydrazinyl-2-oxoethyl)-3-(trifluoromethyl)benzamide (CID 16109340)]. The water extract of Terminalia catappa L. revealed the highest inhibitory effect against the growth of all microbial odor isolates. Hence, our study concludes that the bioactive compounds of T. catappa L. may be used as an appropriate natural source to develop the natural sport deodorant spray in the future.

Tolerance of Cobb-500 broilers to a supplemental Clostridium fermentation solubles broth in the diet

Volatile short-chain fatty acids such as butyric and acetic acid have been supplemented in poultry rations as a feed ingredient and nutritive supplement. A novel Clostridium fermentation solubles broth (MiruTyton), containing short-chain fatty acids, minerals, and amino acids, was supplemented in a standard corn/soybean meal–based ration at a rate of 750, 1,500, 3,000, and 6,000 mg/kg to achieve approximately 277, 554, 1,108, and 2,216 mg/kg of ammonium butyrate in the diet. After 6 wk, supplementation at all levels did not cause significant changes in the blood parameters or any live performance metric of mixed-sex Cobb-500 broilers (N = 1,920). In addition, administering 6,000 mg/kg of MiruTyton caused no significant lesions in any of the tissue examined except for an increase ( P < 0.05) in proventricular gastritis as compared with control. The inclusion of 1,500 and 3,000 mg/kg MiruTyton increased ( P < 0.01) blood globulin as compared with the control group, which indicates a higher concentration of antibodies in circulation. This experiment demonstrates that mixed-sex Cobb-500 broilers can tolerate supplemental ammonium butyrate up to 2,216 mg/kg in the ration with no negative impact to live performance.

Microbiome Diversity and Differential Abundances Associated with Gastrointestinal Symptoms, BMI, Immune Markers, and Fecal Short Chain Volatile Fatty Acid Profiles

Abstract Objectives The gut microbiota and its metabolites – namely short chain volatile fatty acids (SCVFAs) – interact with the digestive, immune, and nervous systems. States of microbiome dysbiosis are highly associated with obesity and GI symptoms, and profiles of SCVFAs, which serve functions as fuel sources and signaling molecules, mimic this dysbiotic state. This study aimed to further our understanding of associations between bacterial diversity and GI symptoms, BMI, immune markers, and SCVFAs and to identify bacteria differentially abundant with changes to the previously mentioned variables. Methods Data (measures of GI distress, BMI, immunoglobulins, fecal proximate analysis, SCVFAs, and 16s RNA sequences) was extracted from a study containing non-celiac gluten-sensitive and control participants. QIIME2 was used to process 16s RNA data, analyze quantitative, qualitative, phylogenetic quantitative, and phylogenetic qualitative measures of alpha and beta diversity and to perform an analysis of composition of microbes (ANCOM) for differential abundances data. Results Many significant differences were seen, namely in multiple measures of alpha diversity for IgG4 (P &amp;lt; 0.018), propionate (P &amp;lt; 0.014), caproate (P &amp;lt; 0.003), heartburn (P &amp;lt; 0.004), urgent need to defecate (P &amp;lt; 0.027), and feelings of incomplete evacuation (P &amp;lt; 0.024). Statistical significance was seen in multiple measures of beta diversity between normal and overweight (P &amp;lt; 0.01), normal and obese (P &amp;lt; 0.005), and overweight and obese BMI (P &amp;lt; 0.016), IgG4 (P &amp;lt; 0.033), propionate (P &amp;lt; 0.001), increased gas (P &amp;lt; 0.024), and urgent need for defecation (P &amp;lt; 0.026). The ANCOM identified multiple species of bacteria differentially abundant with changes to variables. Conclusions Findings suggest differences in both alpha and beta diversity with various GI symptoms, SCVFAs, and BMI. This research supports plans to apply analysis to larger sample sizes to train machine learning classifiers to identify important features of microbial profiles associated with certain SCVFA and markers of health. Funding Sources ETSU (CCRHS, Deans's Research Enhancement Award and CPH, Health Sciences Funding, Honors College Summer Research Fellowship) and Shield Nutraceuticals, LLC.

Fecal Fermentation Profile, Serum Fatty Acid Profile and Measures of Liver Health in Male HIV-infected Versus Non-infected Controls

Abstract Objectives Many persons with an HIV infection and undergoing treatment still experience weight loss, hyperglycemia, hyperlipidemia, gastrointestinal issues (diarrhea and malabsorption), and symptoms of lipodystrophy. Symptoms include NAFLD and liver fibrosis. The gut microbiota and short chain volatile fatty acids (SCVFA) interface with other body systems. Dysbiosis of the gut microbiota due to pharmaceuticals, malabsorption, and chronic diseases is associated with milieu of imbalances indicated by the modification of the SCVFA profile. This study aimed to further elucidate the relationship between gut microbiota fermentation profiles, serum and fecal long chain fatty acid profiles, NAFLD, liver fibrosis, and anthropometric measures in HIV infected males. Methods This research enrolled 14 HIV-infected and 14 non-infected males that were matched for age and body mass index (BMI). Anthropometric measurements BMI and hip to waist ratio were obtained, along with a liver scan for fatty liver and fibrosis using the ARFI ultrasound technique as well as a single blood draw via venipuncture. A full bowel movement was collected for each participant, a small aliquot was collected for future microbiome analysis, and the remainder was freeze-dried and stored at −80 C. Proximate analysis of fecal fat content was analyzed by soxhlet extraction. Fermentation profile of both fecal SCVFA and LCFA, and serum LCFA were analyzed via gas chromatography. Results Significant differences in levels of specific SCVFAs were found between groups, with male controls having significantly higher amounts of acetate (P &amp;lt; 0.046), butyrate (P &amp;lt; 0.033), and valerate (P &amp;lt; .006). Serum LCFA were similar between groups with a few exceptions. Anthropometric data approached statistical significance, with the HIV infected males exhibiting a greater value for liver damage (P = 0.060) and hip to waist ratio (P = 0.015). Conclusions In addition to identifying altered lipid circulation and liver damage, this research suggests differences in microbial communities between HIV-infected and non-infected individuals. Planned future microbiome analysis will help to correlate bacterial populations with altered fecal fermentation profiles. Funding Sources Seed Grant, Center of Excellence in Inflammation, Infectious Diseases and Immunity, ETSU.

A high-rate anaerobic biofilm reactor for biomethane recovery from source-separated blackwater at ambient temperature.

Anaerobic bioreactors for source-separated blackwater are mostly operated at low organic loading rates (OLRs) due to low biodegradability and the potential of ammonia inhibition. In this study, an anaerobic biofilm reactor having conductive carbon fibers as the media was investigated for the high-rate treatment of blackwater collected from vacuum toilets. The bioreactor was operated at different OLRs ranged from 0.77 to 3.01g COD/L-d in four stages for a total operating period of~250days. With the increase of OLRs, the specific methane production rate increased from 105.3 to 304.6ml/L-d with high methane content in biogas (75.5%-83%). The maximum methane yield was achieved at hydraulic retention time (HRT) of 15days. Highest organics and suspended solids removal (80%-83%) were achieved at 20-days HRT, while increased OLRs resulted in diminished removal efficiencies. The state variables, including pH, total ammonia nitrogen, short-chain volatile fatty acids, and soluble chemical oxygen demand, indicated the system had a great capability to withstand the high OLRs. Microbial community analysis revealed that the high performance might be attributed to direct interspecies electron transfer (DIET) facilitated by potentially electroactive bacteria (e.g., Syntrophomonas, Clostridium) and electrotrophic archaea (e.g., Methanosaeta and Methanosarcina species) enriched on the carbon fibers. PRACTITIONER POINTS: An anaerobic biofilm reactor was investigated for biomethane recovery from source-separated blackwater. Conductive carbon fibers were utilized as the media to stimulate enrichment of potentially electroactive methanogenic communities. The bioreactor was operated at ambient temperature for over 250days. High methane production rate and high-quality biogas were achieved at OLRs ranged from 0.77 to 3.01g COD/L-d. Microbial community analysis suggested direct interspecies electron transfer (DIET) between specific electroactive bacteria and electrotrophic archaea.

Transformation analysis of key liquid phase products during lignite fermentation to produce biological hydrogen

There was little research on the changes and interconversion of organic compounds in the intermediate liquid-phase productsin the hydrogen production by anaerobic fermentation of coal. The types and concentrations of the intermediate liquid-phase products are not only related to the efficiency of coal conversion into biohydrogen, but one of the important contents of study on the generation mechanism of biohydrogen from coal. In order to study the change of key liquid phase products in the process of bio-hydrogen production from coal, the simulation experiments of bio-hydrogen production were conducted under suitable environmental conditions using lignite from Daliuta, Shaanxi province. The hydrogen concentration and key liquid phase products were measured using gas chromatography and GC–MS, respectively, to reveal its change. The results show that: (1) there is correspondence between the key liquid phase products and hydrogen yield. The saturated alkanes and cyclic hydrocarbons show a trend of first increasing, then decreasing, and finally increasing, but the changes of proteinaceous materials are just the opposite, which is correspondent to the initial stage, peak stage and terminal stage of hydrogen production, respectively. (2) The short-chain volatile fatty acids are accumulated gradually in the process of hydrogen production, and the short-chain acids of aromatic show a trend of first increasing, then decreasing, increase again and finally decreasing, which is correspondent to the different biochemical reactions, such as the release of small molecules, the utilization of microorganisms, hydrocarbon oxidation and the redegradation of macromolecule. (3) The lipids, aldehydes and ketones are the parent substances of acid production, and the changes are related to the increased acids to a certain extent. This research not only reveals the biochemical effects between gas and liquid phases, but further enriches the theory of bio-hydrogen production from coal.

Effect of pH, yeast extract and inorganic carbon on chain elongation for hexanoic acid production

Several anaerobic bioconversion technologies produce short chain volatile fatty acids and sometimes ethanol, which can together be elongated to hexanoic acid (C6 acid) by Clostridium kluyveri in a secondary fermentation process. Initiatives are needed to further optimize the process. Therefore, five strategies were tested aiming at elucidating their influence on hexanoic acid production from mixtures of acetic acid, butyric acid and ethanol. pH-regulated bioreactors, maintained at pH 7.5, 6.8 or 6.4 led to maximum C6 acid concentrations of, respectively, 19.4, 18.3 and 13.3 g L−1. At pH 6.8, yeast extract omission resulted in a decrease of the hexanoic acid concentration to 12.0 g L−1 while the addition of an inorganic carbon source, such as bicarbonate, for pH control, increased the C6 acid concentration up to 21.4 g L−1. This research provides guidelines for efficient improved production of hexanoic acid by pure cultures of C. kluyveri, contributing to the state of art.

Study of intestinal dysbiosis (“dysbacteriosis”): state of problem and new trends

Intestinal dysbiosis (“dysbacteriosis”) is a clinical and laboratory (clinical and microbiological) secondary syndrome that develops in a number of diseases and clinical syndromes and is characterized by changes in the quantitative and qualitative (species) composition of microbial associations (normal flora) in certain biotopes (large and small intestine) with the translocation of its various representatives into unusual biotopes.&#x0D; The main causes of the development of colic dysbiosis are: antibacterial therapy with the use of broad-spectrum antibiotics; hormone therapy; use of cytostatics; radiation therapy; bowel surgery; acute intestinal infectious diseases (dysentery, salmonellosis, etc.); immunodeficiency states of various genesis; unbalanced nutrition; lack of dietary fiber; excessive consumption of preservatives and xenobiotics; intestinal movement disorders (chronic constipation, diarrhea); mental stress conditions, etc.&#x0D; There are direct (bacteriological cultures) and indirect (determination of short-chain volatile fatty acids by gas-liquid chromatography, respiratory tests, etc.) methods for diagnosing intestinal dysbiosis.&#x0D; Treatment of intestinal dysbiosis (“dysbacteriosis”) should be individualized and complex, taking into account its severity (degree), preferential localization (colon, small intestine), nature of the prevailing conditionally pathogenic microflora, presence of clinical symptoms and its characteristic features. Adequate treating of the underlying disease that caused intestinal dysbiosis; restoration of the impaired functions of the intestine, its parietal (contact, membrane) and abdominal digestion; increasing the overall resistance of the organism due to the restoration of its immunological and non-specific protection; correction of dysbiosis of the colon and small intestine are crucial. Diet, intestinal antibiotics, pro-, prebiotics, synbiotics are important components of treatment. In recent years, fecal transplantation has been more widely applied.

Complete genome sequence of Nitratireductor sp. strain OM-1: A lipid-producing bacterium with potential use in wastewater treatment

Reducing CO2 emissions is necessary to alleviate rising global temperature. Renewable sources of energy are becoming an increasingly important substitute for fossil fuels. An important step in this direction is the isolation of novel, technologically relevant microorganisms. Nitratireductor sp. strain OM-1 can convert volatile short-chain fatty acids in wastewater into 2-butenoic acid and its ester and can accumulate intracellularly esterified compounds up to 50% of its dried cell weight under nitrogen-depleted conditions. It is believed that a novel fatty acid biosynthesis pathway including an esterifying enzyme is encoded in its genome. In this study, we report the whole-genome sequence (4.8 Mb) of OM-1, which comprises a chromosome (3,977,827 bp) and a megaplasmid (857,937 bp). This sequence information provides insight into the genome organization and biochemical pathways of OM-1. In addition, we identified lipid biosynthesis pathways in OM-1, paving the way to a better understanding of its biochemical characterization.

Enhanced biological phosphorus removal using thermal alkaline hydrolyzed municipal wastewater biosolids

This study reports the feasibility of using municipal wastewater biosolids as an alternative carbon source for biological phosphorus removal. The biosolids were treated by a low-temperature, thermal alkaline hydrolysis process patented by Lystek International Inc. (Cambridge, ON, Canada) to produce short-chain volatile fatty acids and other readily biodegradable organics. Two sequencing batch reactors (SBRs) were operated with synthetic volatile fatty acids (SynVFA) and readily biodegradable organics produced from the alkaline hydrolysis of municipal wastewater biosolids (Lystek) as the carbon source, respectively. Municipal wastewaters with different strengths and COD:N:P ratios were tested in the study. The reactors' performances were compared with respect to nitrogen and phosphorus removal. It was observed that phosphorus removal efficiencies were between 98%–99% and 90%–97% and nitrogen removal efficiencies were 78%–81%, and 67% for the SynVFA and Lystek, respectively. However, the kinetics for phosphorus release and uptake during the anaerobic and aerobic stages with Lystek were observed to be significantly lower than SynVFA due to the presence of higher order VFAs (C4 and above) and other fermentable organics in the Lystek.