Effect of ethanol and butanol on autotrophic growth of model homoacetogens

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. carboxidiwrans P7, and 'Butyribacterium methylotrophicum DSM3468'. Experiments to determine inhibitory effects due to product accumulation were carried out using a synthetic mixture of CO:CO2:H-2 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

Impact of formate on the growth and productivity of Clostridium ljungdahlii PETC and Clostridium carboxidivorans P7 grown on syngas

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. [Int Microbiol 2014; 17(4):195-204]Keywords: Clostridium carboxidivorans · Clostridium ljungdhalii · syngas fermentation · biofuels · format

New fecal bacterial signature for colorectal cancer screening reduces the fecal immunochemical test false-positive rate in a screening population

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

Definition of a microbial signature as a predictor of endoscopic post-surgical recurrence in patients with Crohn’s disease

Background and aims: Although there are several effective drugs for the treatment of Crohn’s disease (CD), almost 70% of patients will require surgical resection during their lifetime. This procedure is not always curative, as endoscopic recurrence occurs in 65%–90% of patients in the first year after surgery. The aetiology of the recurrence is unknown; however, several studies have shown how the resident microbiota is modified after surgery. The aim of this study was to evaluate samples from patients with Crohn’s disease before and after an intestinal resection to determine whether there were differences in the abundance of different microbial markers, which may predict endoscopic recurrence at baseline.Methods: In this observational study, a stool sample was obtained from 25 patients with Crohn’s disease before undergoing surgery, recruited at three Catalan hospitals. From each sample, DNA was purified and the relative abundance of nine microbial markers was quantified using qPCR.Results: An algorithm composed of four microbial markers (E. coli, F. prausnitzii phylogroup I, Bacteroidetes, and Eubacteria) showed a sensitivity and specificity of 90.91% and 85.71%, respectively, and a positive and negative predictive value of 83.33% and 92.31%, respectively.Conclusion: A microbial signature to determine patients who will have post-surgical recurrence was identified. This tool might be very useful in daily clinical practice, allowing the scheduling of personalized therapy and enabling preventive treatment only in patients who really require it

Insights into key parameters for bio-alcohol production in syngas fermentation using model carboxydotrophic bacteria

This doctoral thesis deals with the synthesis of two biofuels (bioethanol and biobuthanol) by bacteria. Concretely, the thesis is focused on a group of bacteria able to grow in a simple substrate such as synthesis gas or syngas. Syngas is a mixture of hydrogen, carbon monoxide, and carbon dioxide obtained through the gasification of urban and forestry wastes. The use of syngas as a substrate requires a good knowledge of bacterial metabolism to successfully control acid production and promote alcohol synthesis. To acquire this knowledge, the researcher carried out a set of experiments at lab scale, always using syngas. Among the most significant results, there is the relevance of both the temperature and the bacteria state at the start of the experiments. Additionally, new insights into bacterial metabolism which are applicable at industrial scale were gathered.Aquesta tesi doctoral tracta la producció de dos biocombustibles – el bioetanol i el bioalcohol - per mitjà de microorganismes. En concret, la tesi s'ha centrat en un grup de bacteris capaços de sintetitzar bioalcohols a partir del gas de síntesis o syngas. El syngas és una mescla d’hidrogen, diòxid de carboni i monòxid de carboni que s’obté mitjançant la gasificació de diferents tipus de residus. L’ús d’aquest gas com a substrat requereix un bon coneixement del metabolisme dels bacteris involucrats a fi de controlar amb èxit la producció d'àcids i afavorir la d'alcohols. Aquest coneixement s'ha adquirit amb una sèrie d'experiments avançats a escala de laboratori. Entre els resultats més significatius destaca la rellevància que ha demostrat tenir la temperatura en què creixen els bacteris i l’estat del bacteri en el moment d’inici dels experiments. També s’han aportat nous coneixements sobre el metabolisme bacterià que són aplicables a escala industrial

Insights into key parameters for bio-alcohol production in syngas fermentation using model carboxydotrophic bacteria

This doctoral thesis deals with the synthesis of two biofuels (bioethanol and biobuthanol) by bacteria. Concretely, the thesis is focused on a group of bacteria able to grow in a simple substrate such as synthesis gas or syngas. Syngas is a mixture of hydrogen, carbon monoxide, and carbon dioxide obtained through the gasification of urban and forestry wastes. The use of syngas as a substrate requires a good knowledge of bacterial metabolism to successfully control acid production and promote alcohol synthesis. To acquire this knowledge, the researcher carried out a set of experiments at lab scale, always using syngas. Among the most significant results, there is the relevance of both the temperature and the bacteria state at the start of the experiments. Additionally, new insights into bacterial metabolism which are applicable at industrial scale were gathered.Aquesta tesi doctoral tracta la producció de dos biocombustibles – el bioetanol i el bioalcohol - per mitjà de microorganismes. En concret, la tesi s'ha centrat en un grup de bacteris capaços de sintetitzar bioalcohols a partir del gas de síntesis o syngas. El syngas és una mescla d’hidrogen, diòxid de carboni i monòxid de carboni que s’obté mitjançant la gasificació de diferents tipus de residus. L’ús d’aquest gas com a substrat requereix un bon coneixement del metabolisme dels bacteris involucrats a fi de controlar amb èxit la producció d'àcids i afavorir la d'alcohols. Aquest coneixement s'ha adquirit amb una sèrie d'experiments avançats a escala de laboratori. Entre els resultats més significatius destaca la rellevància que ha demostrat tenir la temperatura en què creixen els bacteris i l’estat del bacteri en el moment d’inici dels experiments. També s’han aportat nous coneixements sobre el metabolisme bacterià que són aplicables a escala industrial

Impact of formate on the growth and productivity of Clostridium ljungdahlii PETC and Clostridium carboxidivorans P7 grown on syngas

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 productivityThe authors thank the Autonomous Government of Catalonia (Generalitat de Catalunya) (2013 FI-DGR) and the Spanish Ministry of Science and Innovation (Best-Energy, CTQ2011-23632, CTM2013-43454-R) for their financial support in this study. LEQUIA and IEA have been recognized as consolidated research groups by the Catalan Government (2014-SGR-1168 and 2014-SGR-2016). RG gratefully acknowledges support from Beatriu de Pinos fellowship (BP-2011-B) and FP7 Marie Curie Career Integration Grants (PCIG13-GA-2013-618593

In vitro Prebiotic Effect of Bread-Making Process in Inflammatory Bowel Disease Microbiome

Inflammatory bowel disease (IBD), including its two main categories (Crohn's disease and ulcerative colitis), has been linked both to gut microbiota and to diet. Bread is a daily food that has a potential capacity as a prebiotic. Our aim was to evaluate different bread-making processes and their effect on fecal colonic microbiota in IBD patients. The microbial composition of several sourdoughs and dough samples was analyzed by high-throughput sequencing of 16S and 18S rRNA genes. Three types of bread, which followed different bread-making processes, were in vitro digested and incubated with feces from IBD patients. Changes in gut microbiota were assessed by a quantitative polymerase chain reaction using specific bacterial sequence targets. Short-chain fatty acid production was also analyzed by gas chromatography. Lactobacillus sanfranciscensis was the dominant lactic acid bacteria species found in sourdough and bread doughs prepared using sourdough, whereas Saccharomyces cerevisiae was the most dominant yeast in all groups, especially in bread doughs before baking. Differences in microbial composition in raw bread doughs were more related to the type of dough and elaboration than to fermentation time lengths. The analysis of in vitro fecal incubations with bread conditions revealed an increase in most bacterial groups analyzed and short-chain fatty acid production, both in Crohn's disease and ulcerative colitis samples. Most remarkable increases in short-chain fatty acid production mirrored higher abundances of Roseburia species. The potential prebiotic properties observed were mainly obtained when using a high quantity of bread, regardless of bread type. Overall, this study highlights the bacterial dynamics within the bread-making process and the potential prebiotic effect in IBD patients