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Background Irritable bowel syndrome (IBS) is a functional disorder affecting around 11% of the world population, which diagnostic is mainly based on clinical parameters. IBS shares many symptoms with other gastrointestinal disorders such as inflammatory bowel disease (IBD), which makes positive diagnosis a difficult task. Aim This work presents the design of a new test, called RAID‐Dx, which is a mathematical algorithm based on the combination of nine faecal microbial markers capable of diagnosing IBS. Methods A cohort consisting of 165 subjects (52 IBS and 52 IBD patients, and 61 healthy controls) was recruited from the Gastroenterology Department of six hospitals. Each patient provided a stool sample from which DNA was extracted, and microbial markers composing RAID‐Dx were analysed by qPCR. The results obtained were used to define and validate the RAID‐Dx algorithm. Results The abundance of the biomarkers included in the algorithm differed according to the diagnosis. RAID‐Dx shows a high capacity to diagnose IBS with a sensitivity of 82.4% and a specificity of 85.7%. RAID‐Dx also reports higher sensitivity and specificity values than faecal calprotectin for IBS and IBD differentiation. Conclusions RAID‐Dx is a noninvasive tool aimed to diagnose IBS with high sensitivity and specificity. The use of this new tool for IBS diagnosis could significantly improve disease management, minimise its misdiagnosis and increase patients’ quality of life

Background and Aims Crohn’s disease and ulcerative colitis evolve with alternate outbreaks and remissions of variable duration in both cases. Despite the advances, about 10-30% of patients do not respond to the treatment after the induction period. Besides, between 20% to 50% further patients need an optimization of the dose to respond the treatment. Recent studies have pointed gut microbiota can play a role in the anti-TNF treatment response. This study aimed to define a bacterial signature that could be used to predict the response of patients to anti-TNF treatment. Methods There were obtained 38 stool samples from 38 IBD patients before starting anti-TNF treatments: Adalimumab, Golimumab or Infliximab. Patients were differentiated in 2 groups: responders and non-responders to biological treatment. From each sample, DNA was purified and used in a qPCR for the quantification of the 8 microbial markers. Results In this proof of concept, the predictive ability to identify anti-TNF treatment responders was analyzed. An algorithm consisting in the combination of 4 bacterial markers showed a high capacity to discriminate between responders and non- responders. The algorithm proved high sensitivity and specificity reporting values of 93.33% and 100% respectively, with a positive predictive value of 100% and a negative predictive value of 75% for predicting response to biologic treatment. Conclusions A specific bacterial signature could beneficiate patients with inflammatory bowel disease predicting the therapeutic effectiveness of an anti-TNF treatment, leading to a personalized therapy, improving the patients’ quality of life, saving costs and gaining time in patient improvement.

Reliable operational procedures for the control of Microbial Electrochemical Technologies (METs) to produce suitable substrates for economically viable downstream applications were investigated. We aimed at levelling key operational conditions in a model electrosynthetic reactor in order to obtain biofuels from carbon dioxide (CO2). The cathodes of two tubular bioelectrochemical systems (BESs) were inoculated with an enriched culture of a carboxydotrophic strain and were operated until stable conversion of CO2 into acetate and ethanol. Both reactors averaged a production of 76 ± 9 mgethanol m−2 d−1 and 120 ± 29 mgacetate m−2 d−1, which were considered crucial for triggering the production of longer carbon chain carboxylates and alcohols in a chain elongation bioreactor. Changes in the current signal and pH were correlated with CO2 depletion and the transition from acetogenesis to solventogenesis in the enriched culture. We show that in-line monitoring of pH and electron consumption are meaningful operational variables to differentiate between the two biological processes, and open the door to develop new approaches to control the bioelectro-recycling of CO2 into biofuels by METs.

Background Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS) are two intestinal disorders with unknown aetiology. IBD presents two main forms which are Crohn’s disease (CD) and ulcerative colitis (UC). It has been reported recently that bacterial communities present in the colon of patients with either IBD or IBS are structurally different compared to those found in healthy individuals. This dysbiosis mainly consists of a decrease of butyrate producing bacteria and, therefore, the recovery of this metabolic group should be at the baseline of any successful treatment. The main goal of this proof-of-concept study was to test the capacity of a new prebiotic of selected dietary fibre obtained from grape to balance the dysbiosis found in patients with different intestinal disorders. Methods In this study, fresh faecal samples from 6 healthy subjects, 3 CD, 3 UC, and 3 IBS were collected at the Hospital Universitari Dr. Josep Trueta. Fresh samples were diluted 1:5 with fermentation buffer and incubated with 200 mg of prebiotic at 37 ºC under agitation for 72 h. Results were compared with those obtained with various commercial prebiotics after simulating in vitro digestion: inulin, grape pectin, and grape seed extract (GSPE). Total DNA was extracted and the abundance of butyrate-producing bacterial markers: F. prausnitzii (Fpra), its two phylogroups (PHGI and PHGII), Roseburia spp. (Ros) and S. variabile (Sva) was analysed by qPCR. Bacterial activity was determined by measuring short chain fatty acids (SCFA) concentration (butyrate, acetate, and propionate) by gas chromatography. Results The abundance of all butyrate-producing bacteria analysed increased after incubation with the new prebiotic. Among them, Ros presented significantly higher abundance values with respect to negative control in healthy, CU, and IBS patients. It also showed a significant increase in all individuals analysed compared to inulin, grape pectin, and GSPE. Fermentation of the tested new prebiotic, produced significantly higher concentrations of SCFA (p < 0.001) when compared to negative control and all other commercial fibres. Acetate concentration was a 241% higher than negative control, followed by butyrate (187%), and propionate (169%). Conclusion The studied prebiotic produces in vitro an increase of the abundance and enhancement of the metabolism of butyrate-producing bacteria, when compared to commercial prebiotics. These results suggest that this new fibre is a promising prebiotic to be used in promotion of intestinal microbiota restoration at mucosa.

Guidelines recommend routine screening for colorectal cancer (CRC) in asymptomatic adults starting at age 50. The most extensively used noninvasive test for CRC screening is the fecal immunochemical test (FIT), which has an overall sensitivity for CRC of approximately 61.0%-91.0%, which drops to 27.0%-67.0% for advanced adenomas. These figures contain a high false-positive rate and a low positive predictive value. This work aimed to develop a new, noninvasive CRC screening tool based on fecal bacterial markers capable of decreasing FIT false-positive rates in a FIT-positive population. We defined a fecal bacterial signature (RAID-CRC Screen) in a proof-of-concept with 172 FIT-positive individuals and validated the obtained results on an external cohort of 327 FIT-positive subjects. All study participants had joined the national CRC screening program. In the clinical validation of RAID-CRC Screen, a sensitivity of 83.9% and a specificity of 16.3% were obtained for the detection of advanced neoplasm lesions (advanced adenomas and/or CRC). FIT 20 μg/g produced 184 false-positive results. Using RAID-CRC Screen, this value was reduced to 154, thus reducing the false-positive rate by 16.3%. The RAID-CRC Screen test could be implemented in CRC screening programs to allow a significant reduction in the number of colonoscopies performed unnecessarily for FIT-positive participants of CRC screening programs JGG, XA, MSP, MS SRP, JA, LO, MM are employees from GoodGut, a company that has received private and public funding: RTC-2016-5017-1 (Spanish Ministry of Economy, Industry and Competitivity (MINECO)); SNEO-20151529 (Neotec)

In constructed wetlands (CW), denitrification usually accounts for > 60% of nitrogen removal and is supposedly affected by wetland management practices, such as dredging (and plant removal). These practices cause an impact in sediment properties and microbial communities living therein. We have quantified the effects of a sediment dredging event on dissimilatory nitrite reduction by analysing the structure and activities of the microbial community before and after the event. Potential rates for nitrate reduction to ammonia and denitrification were in accordance with changes in the physicochemical conditions. Denitrification was the predominant pathway for nitrite removal (> 60%) and eventually led to the complete removal of nitrate. On the contrary, dissimilatory nitrite reduction to ammonia (DNRA) increased from 5 to 18% after the dredging event. Both actual activities and abundances of 16S rRNA, nirK and nirS significantly decreased after sediment dredging. However, genetic potential for denitrification (qnirS + qnirK/q16S rRNA) remained unchanged. Analyses of the 16S rRNA gene sequences revealed the importance of vegetation in shaping microbial community structures, selecting specific phylotypes potentially contributing to the nitrogen cycle. Overall, we confirmed that sediment dredging and vegetation removal exerted a measurable effect on the microbial community, but not on potential nitrite + nitrate removal rates. According to redundancy analysis, nitrate concentration and pH were the main variables affecting sediment microbial communities in the Empuriabrava CWs. Our results highlight a high recovery of the functionality of an ecosystem service after a severe intervention and point to metabolic redundancy of denitrifiers. We are confident these results will be taken into account in future management strategies in CWs.

Background Crohn’s disease (CD) and ulcerative colitis (UC) evolve with alternate outbreaks and remissions of variable duration. Tumour necrosis factor α antagonists (anti-TNFα) have enhanced the treatment of patients with inflammatory bowel disease (IBD), improving the patient’s quality of life by reducing the number of surgeries and hospitalizations. Despite these advances, about 10–30% of patients do not respond to the treatment after the induction period. Recent studies have pointed, on one hand, gut microbiota can play a role in the anti-TNFα treatment response as gram-positive bacteria can modulate the response of NOD proteins and, on the other hand, gram-negative bacteria can stimulate TLR4 receptors causing activation of NFkß. This study aimed to define a microbial signature that could be used to predict the response of patients with CD and UC to anti-TNFα treatment. Methods This observational study consisted of obtaining a stool sample from 38 IBD patients before starting an anti-TNFα treatment. Patients were recruited at Hospital Universitari Dr. Josep Trueta (Girona) and Hospital Universitari de Bellvitge (l’Hospitalet de Llobregat). During the one-year follow-up period, disease activity levels, faecal calprotectin evolution, and anti-TNFα antibody levels were analysed to assess response to treatment, differentiating 2 groups: responders and non-responders. From each sample, DNA was purified and used in a qPCR for the quantification of the following markers: F. prausnitzii (Fpra) and its phylogroups (PHG-I and PHG-II), E. coli (Eco), A. muciniphila (Akk), Ruminococcus sp. (Rum), Bacteroidetes (Bac), M. smithii (Msm), and the total bacterial load (Eub). Results In this proof of concept, the predictive ability to identify anti-TNFα treatment responders was analysed. Individually, none of biomarkers demonstrated the ability to differentiate between groups with high sensitivity and specificity. However, an algorithm consisting of the combination of 5 microbial markers (Msm, Fpra, PHGII, Rum, and Eub) showed a high capacity to discriminate between responders and non-responders. The algorithm proved high sensitivity and specificity reporting values ​​of 93.33% and 100%, respectively, with a positive predictive value of 100% and a negative predictive value of 75% for predicting response to biologic treatment. Conclusion A specific microbial signature could beneficiate patients with IBD by predicting the therapeutic effectiveness of an anti-TNFα treatment, which could lead to a personalized therapy, improving the patients’ quality of life, saving costs, and gaining time in patient recovery.A larger prospective study will be needed to validate these results.

Background Dysbiosis is a widely used but unspecific term. It has been defined as any change in the composition of resident microbial communities relative to the ones found in healthy individuals. But it is still unclear which are the appropriate communities to define it and the reference values to measure it. Different studies have described dysbiosis in various diseases such as Inflammatory Bowel Disease (IBD), diabetes, rheumatoid arthritis, and autism, among others. Besides, the microbiota can be altered by transient factors such as antibiotics, diet, stress, or infections. Therefore, different degrees of severity can be associated with the term dysbiosis from which pathological and transient dysbiosis can be differentiated. This work aimed at defining more specifically the term intestinal dysbiosis and to differentiate both transient and pathological dysbiosis. Methods Fifteen key microbial markers belonging to the principal families, classes and orders found in the human intestinal microbiota were accurately selected based on its functionality: F. prausnitzii (Fpra), E. coli (Eco), Firmicutes (Fir), Bacteroidetes (Bac), A. muciniphila (Akk), Ruminococcus sp. (Rum), Roseburia sp. (Ros), Gammaproteobacteria (Gam), Clostridia cluster I (Clo), Clostridia cluster XIV (XIV), Enterococcus sp., Lactobacillus sp. (Lac), C. albicans (Can), M. smithii (Msm), and the total bacterial load (Eub). The dysbiosis was defined using stool samples in a cohort of healthy subjects (n=24) and then validated with 9 patients diagnosed with intestinal diseases 4 IBD and 2 Irritable Bowel Syndrome (IBS)). Total DNA was extracted and the abundance of microbial markers was analysed by qPCR. Together with the establishment of the most common range in which each microbial marker was found, an index to define the pathological dysbiosis was calculated. Results Almost all healthy subjects analysed presented one or two slightly altered markers. The affected microbial markers in this “transient dysbiosis” were Fpra, Akk, and Ros, which are indicative of the mucous layer state, Firm as indicative of the lifestyle and fiber intake, Gam as characteristic of the pro-inflammatory state of the gut, and Msm as an altered intestinal habit and gas production. All patients analyzed (IBD and IBS) presented alterations mainly of the bacteria inhabiting the mucosa and an alteration of the opportunistic species related to the disrupted mucous layer and defining “pathological dysbiosis”. Conclusion This study establishes an appropriate abundance range of key microbial markers in the gut, leading to a specific definition of dysbiosis which allows to differentiate the pathological from the transient dysbiosis. These results need further validation in a larger patient cohort.

Background Inflammatory Bowel Disease (IBD) is a clinical condition of the gastrointestinal tract of unknown aetiology. The two main forms of IBD are Crohn’s disease (CD) and Ulcerative colitis (UC). Recently, it has been reported that the bacterial communities present in the colon of patients with IBD are structurally different compared with those in healthy individuals. This particular dysbiosis consists of a decrease of butyrate producing bacteria and an increase of the pro-inflammatory species. The goal of this work was to test a new prebiotic of selected dietary fibre made from grape for its capacity to balance the dysbiosis typically found in patients with intestinal disorders. Methods Faecal samples from 16 healthy subjects and 11 IBD patients (5 CD and 6 UC) were collected by the Hospital Universitari Dr. Josep Trueta. Fresh stool samples were incubated with 200 mg, 600 mg of prebiotic, and 200 mg of apple pectin. A negative control without substrate addition was also performed. The tubes were incubated under continuous stirring for 72 hours at 37 ºC in semi-anaerobic atmosphere. Total DNA was extracted and the abundances of butyrate-producing bacterial markers (Faecalibacterium prausnitzii, and its phylogroups I and II, Roseburia hominis and Subdolinogranulum variabile) were analysed by qPCR. Concentrations of both butyrate and acetate were determined by gas chromatography as an indication of the bacterial metabolic activity. Results A significant increase of butyrate producing species, such as S. variabile, R. hominis and F. prausnitzii was observed in CD and UC samples when incubated with 200 mg of prebiotic compared with the negative control. F. prausnitzii phylogroup II, which is underrepresented in UC patients, also increased. No differences were found when samples were incubated with 600 mg. Regarding apple pectin, the increase on the abundance of butyrate producing bacteria was higher than the prebiotic in UC samples. In samples from healthy subjects, an increase in the butyrate producing species abundances was observed in both concentrations of prebiotic when compared with the negative control. In those samples no differences were observed when comparing apple pectin with the prebiotic. Concerning butyrate and acetate production, these substances increased in all prebiotic-supplemented samples when compared with the negative control. Conclusion The studied prebiotic causes an increase of the abundance and activity of butyrate-producing bacteria in both IBD patients and healthy subjects. These results points to this new dietary fibre as a promising prebiotic to maintain eubiosis and to promote the microbiota restoration of the intestinal mucosa.

Background Colorectal cancer is the second commonest cause of cancer mortality. Some countries are implementing colorectal cancer screening to detect lesions at an early stage using non-invasive tools like the faecal immunochemical test. Despite affordability, this test shows a low sensitivity for precancerous lesions and a low positive predictive value for colorectal cancer, resulting in a high false-positive rate. Aim To develop a new, non-invasive colorectal cancer screening tool based on bacterial faecal biomarkers, which in combination with the faecal immunochemical test, could allow a reduction in the false-positive rate. This tool is called risk assessment of intestinal disease for colorectal cancer (RAID-CRC). Methods We performed both the faecal immunochemical test and the bacterial markers analysis (RAID-CRC test) in stool samples from individuals with normal colonoscopy (167), non-advanced adenomas (88), advanced adenomas (30) and colorectal cancer (48). All the participants showed colorectal cancer-associated symptoms. Results Performance of the faecal immunochemical test for advanced neoplasia (ie advanced adenoma and colorectal cancer) was determined by using the cut-off value established in Catalonia (20 µg haemoglobin/g of faeces) for a population-based screening approach. Sensitivity and specificity values of 83% and 80%, respectively, and positive and negative predictive values of 56% and 94%, respectively, were obtained. When both the immunological and the biological analysis were combined, the corresponding values were 80% and 90% for sensitivity and specificity, respectively, and 70% and 94% for positive and negative predictive values, respectively, resulting in a 50% reduction of the false-positive rate. Conclusions RAID-CRC test allows a substantial reduction in the faecal immunochemical test false-positive results (50%) in a symptomatic population. Further validation is indicated in a colorectal cancer-screening scenario.

Clostridia are well-known organisms within the scientific community, and many aspects of their life cycle have been studied. Autotrophic strains are especially interesting as microbial cell factories for industrial purposes. Carboxydotrophic clostridia can use CO2/H2 and/or CO as their only carbon and reducing power sources, and they produce alcohols and acids. Both products can be used as either biofuels or feedstock chemicals for many industrial processes, confirming the control of carboxydotrophic clostridia metabolism as one of the most profitable scientific ambitions to be explored. Here, we review the current state of research on alcohol production by carboxydotrophic clostridia, including a comprehensive overview of their metabolic pathways and the key experimental variables that govern alcohol production. Additionally, the genetic and genomic tools for selective and enhanced solvent production, which are currently under intense development, are discussed. In this context, this review covers the main genetic engineering methods that have been utilized to improve the capabilities of solventogenic carboxydotrophic bacteria The review was prepared within the framework of the fellowship 2013 FI-DGR from Catalan Government and projects Best-Energy CTQ2011-23632 and CTM2013-43454-R from Spanish Ministry. LEQUIA and [BA are recognized as consolidated research groups by the Catalan Government (2014-SGR-1168 and 2014-SGR-2016). Ramon Ganigue gratefully acknowledges support from the Beatriu de Pinos Fellowship (BP-2011-B) and FP7 Marie Curie Career Integration Grants (PCIG13-GA-2013-618593

Gasification of sewage sludge allows the recovery of energy, and produces a mix of CO, CO2 and H2 called synthesis gas (or syngas), which can be fermented by acetogenic bacteria to added-value products. This work presents the conversion of syngas to organic acids and alcohols using both pure and mixed cultures. Pure culture kinetic experiments with Clostridium carboxidivorans P7 resulted in the production of high concentrations of acetate (454 mgC/L) and ethanol (167 mgC/L). The pH was the main factor driving solventogenesis, with about 50% of the products in the form of alcohols at pH 5. Conversely, laboratory-scale experiments using a carboxydotrophic mixed culture of the genus Clostridium enriched from anaerobic digester sludge of a municipal wastewater treatment plant was capable of producing mainly butyrate, with maximum concentration of 1,184 mgC/L.

The high genetic similarity between some carboxydotrophic bacteria does not allow for the use of common sequencing techniques targeting the 16S rRNA gene for species identification. 16S rRNA sequencing fails to discriminate among Clostridium ljungdahlii and 'Clostridium autoethanogenum', despite this two species exhibit significant differences in CO2 assimilation and alcohol production. In this work we designed PCR primers targeting for the DNA gyrase subunit A (gyrA) and a putative formate/nitrite transporter (fnt) to specifically detect the presence of 'C. autoethanogenum', C. ljungdahlii or Clostridium carboxidivorans. We could confirm the simultaneous presence of C. ljungdahlii and 'C. autoethanogenum' in different bioreactors, and a preference of the latter for high CO2 content.

Research efforts aimed at increasing ethanol and butanol productivity from syngas are currently gaining attention. For most model carboxydotrophic bacteria, production rates, yields and maximum product titres have been studied in detail, but little is known on alcohol toxicity in these bacteria. The aim of this work was to investigate the inhibitory effects of ethanol and butanol on the growth of Clostridium ljungdahlii PETC, C. carboxidivorans P7, and 'Butyribacterium methylotrophicum DSM3468'. Experiments to determine inhibitory effects due to product accumulation were carried out using a synthetic mixture of CO:CO2:H2 as a substrate. These conditions were chosen to mimic gaseous effluents of biomass and waste gasification plants. Inhibition effects were recorded as changes in growth parameters. No significant inhibition was observed for ethanol at concentrations below 15 g/L. The three species exhibited higher sensitivity to butanol. Half inhibition constants for butanol could be estimated for P7 (IC50 = 4.12 g/L), DSM3468 (IC50 = 1.79 g/L), and PETC (IC50 = 9.75 g/L). In conclusion, at least for the tested strains, alcohol toxicity is not an immediate handicap for increasing alcohol production of the tested homoacetogenic strains.

Background Inflammatory bowel disease (IBD) is defined as a group of autoimmune diseases that affects the digestive tract by causing chronic inflammatory processes. Crohn’s disease (CD) is one of the major types of IBD. Although there are several efficient drugs for its treatment, almost 80% of patients will require an intestinal resection throughout their lives. Some bacterial species found in faecal samples can be used as indicators to diagnose and monitor activity in CD patients. However, this methodology has not yet been tested in patients that underwent an intestinal resection. The aim of this study was to investigate the changes in the abundance of these species associated with total or partial intestinal resection. Methods In this study, we used 30 faecal samples from patients diagnosed with CD in remission withdrawn from the Biobank of the Hospital Universitari Dr. Josep Trueta of Girona. Fifteen samples corresponded to patients who underwent an intestinal resection. The following markers were quantified by qPCR: Faecalibacterium prausnitzii (Fpra), F. prausnitzii phylogroup I (PHG-I), F. prausnitzii phylogrup II (PHG-II), Escherichia coli (Eco), Akkermansia muciniphila (Akk), Ruminococcus sp. (Rum), Bacteroidetes (Bac) and Methanobrevibacter smithii (Msm). Results The abundances of Fpra, PHG-I, PHG-II, Rum, and Msm were significantly lower (p < 0.05) in resected CD patients, whereas Eco was significantly more abundant in those patients. No significant differences were observed in the abundances of Akk and Bac. Conclusion In resected CD patients, beneficial butyrate-producing bacteria are underrepresented, whereas pro-inflammatory species are overpopulated. Any quantitative relationship of these indicators with the relapse probability would help to stratify these patients for a better orientation of therapeutic strategies.

Background Crohn disease (CD) and Ulcerative colitis (UC) are characterised by episodes of exacerbations and remissions. Monitoring disease activity based on intestinal lesion is mandatory prior to any change in the therapeutic strategy. Colonoscopy is the gold standard technique to monitor the disease activity in IBD patients, but it is usually discarded because of costs and risk issues. The concentration of Faecal Calprotectin (FC) is widely used as a non-invasive marker of inflammation of the intestinal mucosa, allowing the assessment of the disease activity. Recently, different studies have demonstrated that certain microbial species, part of intestinal microbiota which can be detected in stool samples, are capable of correlating with disease activity in CD and UC patients. The purpose of this study was to analyse the correlation between these microbial indicators and the FC to monitor the disease activity in CD and UC patients. Methods FC levels were used to define inflammatory disease activity, the predetermined cut-off of 250 μg/g of faeces was used, higher values indicated an active inflammation and lower values indicated disease in remission. Two cohorts consisting of 61 patients of CD (25 with active inflammation and 36 with remission) and 90 of UC (42 with active inflammation and 48 with remission) were recruited by the Gastroenterology department of 4 Catalan hospitals. A sample of faeces was collected from each patient. FC and the following markers were quantified by qPCR: Faecalibacterium prausnitzii (Fpra), Escherichia coli (Eco), Akkermansia muciniphila (Akk), Ruminococcus sp. (Rum), Bacteroidetes (Bac) and Methanobrevibacter smithii (Msm) for each sample. Results The bacterial markers presented different behaviour depending on the disease analysed. The abundances of Eco and Bac were higher in CD with active inflammation compared with CD with remission. In contrast, no significant differences were found for Fpra, Akk, Rum, and Msm. Besides, a significant positive correlation between Eco abundance and FC levels (0.280, p = 0.029) and a significant negative correlation between Msm and FC levels (−0.299, p = 0.021) were observed. According UC patients, while the abundance of Eco was higher in patients with active inflammation, the abundance of Rum was significantly less abundant. No significant differences were found for Fpra, Akk, Bac, and Msm. Moreover, we also observed a significant negative correlation between Rum and FC levels (−0.308, p = 0.003, respectively). Conclusion The abundance of Eco and Msm in CD patients and the abundance of Rum in UC patients correlate to FC in order to determine inflammatory disease activity. So, these markers can also be an accurate discriminator of active disease in CD and UC patients.

To date acetate is the main product of microbial electrosynthesis (MES) from carbon dioxide (CO 2 ). In this work a tubular bioelectrochemical system was used to carry out MES and enhance butyrate production over the other organic products. Batch tests were performed at a fixed cathode potential of − 0.8 V vs SHE. The reproducibility of the results according to previous experiments was validated in a preliminary test. According to the literature butyrate production could take place by chain elongation reactions at low pH and high hydrogen partial pressure (p H2 ). During the experiment, CO 2 supply was limited to build up p H2 and trigger the production of compounds with a higher degree of reduction. In test 1 butyrate became the predominant end-product, with a concentration of 59.7 mMC versus 20.3 mMC of acetate, but limitation on CO 2 supply resulted in low product titers. CO 2 limitation was relaxed in test 2 to increase the bioelectrochemical activity but increase p H2 and promote the production of butyrate, what resulted in the production of 87.5 mMC of butyrate and 34.7 mMC of acetate. The consumption of ethanol, and the presence of other products in the biocathode (i.e. caproate) suggested that butyrate production took place through chain elongation reactions, likely driven by Megasphaera sueciensis ( > 39% relative abundance). Extraction and concentration of butyrate was performed by liquid membrane extraction. A concentration phase with 252.4 mMC of butyrate was obtained, increasing also butyrate/acetate ratio to 16.4. The results are promising for further research on expanding the product portfolio of MES This research was financially supported by the Spanish Ministry of Economy and Competitiveness (CTQ 2014-53718-R) and the University of Girona (MPCUdG2016/137). P. B-V gratefully acknowledges the Catalan Government for the pre-doctoral grant received (2015FI-B2 00076). R.G. gratefully acknowledges support from Ghent University BOF postdoctoral fellowship (BOF15/PDO/068). LEQUIA and EcoAqua have been recognised as consolidated research group by the Catalan Government (Refs. 2014-SGR-1168 and 2014-SGR-484, respectively)

Incubation of carboxydotrophs at 37. °C provides optimal conditions for their growth. However, a fast accumulation of organic acids, specifically acetate, during the exponential growth phase may result in low alcohol production and substrate consumption due to a phenomenon known as "acid crash". The present work investigates growth and productivity of Clostridium carboxidivorans P7 at two incubation temperatures. At 37. °C the culture was not able to override the "acid crash", resulting in low ethanol titers (1.56. mM). On the other hand, lower metabolic rates at 25. °C enhanced ethanol and butanol production (32.1 and 14.5. mM, respectively). Moreover, at low temperatures, hexanol and caproic acid were also produced at significant concentrations, 8.21 and 9.02. mM respectively, among the highest values reported for P7. Our results demonstrate that production of biofuels with longer carbon chains molecules may be enhanced incubating syngas-fermenting acetogenic bacteria at sub-optimal temperatures The authors would like to thank the Generalitat de Catalunya (2013 FI-DGR) and Spanish Ministry (CTQ2014-53718-R and CTM2013-43454-R) for their financial support in this study. LEQUIA and IEA are recognized as consolidated research groups by the Generalitat de Catalunya (2014-SGR-1168 and 2014-SGR-2016). R.G. gratefully acknowledges support from Beatriu de Pinos fellowship (BP-2011-B) and FP7 Marie Curie Career Integration Grants (PCIG13-GA-2013-618593)

The current energy model based on fossil fuels is coming to an end due to the increase in global energy demand. Biofuels such as ethanol and butanol can be produced through the syngas fermentation by acetogenic bacteria. The present work hypothesizes that formate addition would positively impact kinetic parameters for growth and alcohol production in Clostridium ljungdahlii PETC and Clostridium carboxidivorans P7 by diminishing the need for reducing equivalents. Fermentation experiments were conducted using completely anaerobic batch cultures at different pH values and formate concentrations. PETC cultures were more tolerant to formate concentrations than P7, specially at pH 5.0 and 6.0. Complete growth inhibition of PETC occurred at sodium formate concentrations of 30.0 mM; however, no differences in growth rates were observed at pH 7.0 for the two strains. Incubation at formate concentrations lower than 2.0 mM resulted in increased growth rates for both strains. The most recognizable effects of formate addition on the fermentation products were the increase in the total carbon fixed into acids and alcohols at pH 5.0 and pH 6.0, as well as, a higher ethanol to total products ratio at pH 7.0. Taken all together, these results show the ability of acetogens to use formate diminishing the energy demand for growth, and enhancing strain productivity.

Microorganisms are responsible for the decomposition of plant litter due to their enhanced enzyme capabilities. Among extracellular enzymes, those involved in lignin decomposition are especially relevant in leaf degradation. However, the knowledge of the bacterial contribution to the decomposition of phenol-derived compounds in submerged leaf litter is limited. We have used the large unit of the multicomponent bacterial phenol hydroxylase (LmpH) as a genetic proxy to describe changes in the phenol-degrading bacterial community during the decomposition of Platanus acerifolia leaves in a forested stream. Significant differences were found in the phenol-degrading community when three decomposition stages, initial (day 7), midterm (day 58), and late (day 112), were compared. Estimated Shannon's diversity values decreased significantly from 1.93 (initial) to 0.98 (late). According to the deduced amino acid sequences and the corresponding theoretical kinetic parameters of phenol hydroxylases, the initial community showed a low degree of specialization, presumably resulting from random colonization of leaves. At the late decomposition stage, the bacterial community became more specialized, and LmpH genes similar to high-affinity phenol hydroxylases of Comamonas sp. and Burkholderia cepacia increased. The observed changes in the bacterial community suggested an active role of bacteria during litter decomposition in aquatic environments.