Performance intensification of a stirred bioreactor for fermentative biohydrogen production.

In this study, the biohydrogen (bioH2) production of a microbial consortium was optimized by adjusting the type and configuration of two impellers, the mixing regimen and the mass transfer process (KLa coefficients). A continuous stirred-tank reactor (CSTR) system, with a nonstandard geometry, was characterized. Two different mixing configurations with either predominant axial (PB4 impeller) or radial pumping (Rushton impeller) were assessed and four different impeller configurations to produce bioH2. The best configuration for an adequate mixing time was determined by an ANOVA analysis. A response surface methodology was also used to fully elucidate the optimal configuration. When the PB4 impellers were placed in best configuration, c/Dt = 0.5, s/Di = 1, the maximum bioH2 productivity obtained was 440 mL L-1 hr-1, with a bioH2 molar yield of 1.8. The second best configuration obtained with the PB4 impellers presented a bioH2 productivity of 407.94 mL L-1 hr-1. The configurations based on Rushton impellers showed a lower bioH2 productivity and bioH2 molar yield of 177.065 mL L-1 hr-1 and 0.71, respectively. The experiments with axial impellers (PB4) showed the lowest KLa coefficient and the highest bioH2 production, suggesting that mixing is more important than KLa for the enhanced production of bioH2.

Intensification of Hydrogen Production by a Co-culture of Syntrophomonas wolfei and Rhodopseudomonas palustris Employing High Concentrations of Butyrate as a Substrate.

The purpose of this study is to present an effective form of developing a sequential dark (DF) and photo (PF) fermentation using volatile fatty acids (VFAs) and nitrogen compounds as bonding components between both metabolic networks of microbial growing in each fermentation. A simultaneous (co-)culture of Syntrophomonas wolfei (with its ability to consume butyrate and produce acetate) and Rhodopseudomonas palustris (that can use the produced acetate as a carbon source) performed a syntrophic metabolism. The former bacteria consumed the acetate/butyrate mixture reducing the butyrate concentration below 2.0 g/L, permitting Rhodopseudomonas palustris to produce hydrogen. Considering that the inoculum composition (Syntrophomonas wolfei/Rhodopseudomonas palustris) and the nitrogen source (yeast extract) define the microbial biomass specific productivity and the butyrate consumption, a response surface methodology defined the best inoculum design and yeast extract (YE) yielding to the highest biomass concentration of 1.1 g/L after 380.00 h. A second culture process (without a nitrogen source) showed the biomass produced in the previous culture process yields to produce a total cumulated hydrogen concentration of 3.4 mmol. This value was not obtained previously with the pure strain Rhodopseudomonas palustris if the culture medium contained butyrate concentration above 2.0 g/L, representing a contribution to the sequential fermentation scheme based on DF and PF.

Enhanced carotenoid production by Rhodopseudomonas palustris ATCC 17001 under low light conditions.

Carotenoids (CD) are biological pigments produced for commercial purposes. Therefore, it is necessary to study and determine the optimal conditions for increased CD production. There is no consensus in the literature about the conditions that increase CD production. Some authors stated that CD will be preferentially produced at low light intensities, at this adverse condition, microorganism will increase CD production as a survival response mechanism to get more energy. Other authors have mentioned that CD concentrations increase as the light intensity supplied increases, to avoid the overexposure of light and in turn photo-inhibition. Additionally, to increase the specific CD production is also necessary to increase the amount of biomass. In this work, the ammonium concentration (high (HAC) and low (LAC)) and the low light (LL) intensity effect on the CD production was evaluated. Data showed that a high CD-specific concentration of 8.8 mg/gcell was obtained by using R. palustris ATCC 17001 under HAC and LL intensity. CD production was similar at HAC and LAC, suggesting that the light intensity has a greater effect on the specific CD concentration than the nitrogen concentration. In general, the results showed a low biomass production compared to the literature, with high CD synthesis.

Evaluation of the antinociceptive effect of Rosmarinus officinalis L. using three different experimental models in rodents.

The rationale of this investigation was to examine the antinociceptive effect of an ethanol extract of Rosmarinus officinalis (RO) aerial parts, using three different experimental models: acetic acid-induced writhing test and formalin test in mice; and a model of arthritic pain: "pain-induced functional impairment model in the rat (PIFIR model)". The antinociceptive efficacies were evaluated using several dose-response curves and time courses. The antinociceptive effects from RO extract were compared with the antinociceptive effect of either tramadol (TR: 3.16-50 mg/kg, i.p. in mice, and 1.0-31.62 mg/kg, i.p. in rats) or acetylsalicylic acid (AA: 31.62-562.32 mg/kg, p.o.). RO extract (10-300 mg/kg, p.o.) significantly (P < 0.001) reduced the number of writhing movement induced by the i.p. administration of acetic acid solution in a dose-dependent way (ED50 = 108.84 mg/kg, whereas, TR showed an ED50 = 12.38 mg/kg). In addition, RO extract (30-300 mg/kg) significantly (P < 0.001) inhibited licking and shaking behaviours in both early (neurogenic pain) and in the late (inflammatory pain) phases of the formalin test. These effects were like those produced by TR. Concerning the results using the PIFIR model, RO extract (30-3000 mg/kg, p.o.) like either TR or AA, produced a significant (P < 0.001) and dose-dependent antinociceptive response in rats (RO: ED50 = 222.78 mg/kg versus TR: ED50 = 11.06 mg/kg and AA: ED50 = 206.13 mg/kg). These results strongly suggest that aerial parts of RO possess antinociceptive and anti-inflammatory activity, and reinforce the use of this plant in folk medicine.

Insights into Butyrate Production in a Controlled Fermentation System via Gene Predictions.

Butyrate is a common fatty acid produced in important fermentative systems, such as the human/animal gut and other H2 production systems. Despite its importance, there is little information on the partnerships between butyrate producers and other bacteria. The objective of this work was to uncover butyrate-producing microbial communities and possible metabolic routes in a controlled fermentation system aimed at butyrate production. The butyrogenic reactor was operated at 37°C and pH 5.5 with a hydraulic retention time of 31 h and a low hydrogen partial pressure (PH2). High-throughput sequencing and metagenome functional prediction from 16S rRNA data showed that butyrate production pathways and microbial communities were different during batch (closed) and continuous-mode operation. Lactobacillaceae, Lachnospiraceae, and Enterococcaceae were the most abundant phylotypes in the closed system without PH2 control, whereas Prevotellaceae, Ruminococcaceae, and Actinomycetaceae were the most abundant phylotypes under continuous operation at low PH2. Putative butyrate producers identified in our system were from Prevotellaceae, Clostridiaceae, Ruminococcaceae, and Lactobacillaceae. Metagenome prediction analysis suggests that nonbutyrogenic microorganisms influenced butyrate production by generating butyrate precursors such as acetate, lactate, and succinate. 16S rRNA gene analysis suggested that, in the reactor, a partnership between identified butyrogenic microorganisms and succinate (i.e., Actinomycetaceae), acetate (i.e., Ruminococcaceae and Actinomycetaceae), and lactate producers (i.e., Ruminococcaceae and Lactobacillaceae) took place under continuous-flow operation at low PH2. IMPORTANCE This study demonstrates how bioinformatics tools, such as metagenome functional prediction from 16S rRNA genes, can help understand biological systems and reveal microbial interactions in controlled systems (e.g., bioreactors). Results obtained from controlled systems are easier to interpret than those from human/animal studies because observed changes may be specifically attributed to the design conditions imposed on the system. Bioinformatics analysis allowed us to identify potential butyrogenic phylotypes and associated butyrate metabolism pathways when we systematically varied the PH2 in a carefully controlled fermentation system. Our insights may be adapted to butyrate production studies in biohydrogen systems and gut models, since butyrate is a main product and a crucial fatty acid in human/animal colon health.

Controlled continuous bio-hydrogen production using different biogas release strategies.

Dark fermentation for bio-hydrogen (bio-H2) production is an easily operated and environmentally friendly technology. However, low bio-H2 production yield has been reported as its main drawback. Two strategies have been followed in the past to improve this fact: genetic modifications and adjusting the reaction conditions. In this paper, the second one is followed to regulate the bio-H2 release from the reactor. This operating condition alters the metabolic pathways and increased the bio-H2 production twice. Gas release was forced in the continuous culture to study the equilibrium in the mass transfer between the gaseous and liquid phases. This equilibrium depends on the H2, CO2, and volatile fatty acids production. The effect of reducing the bio-H2 partial pressure (bio-H2 pp) to enhance bio-H2 production was evaluated in a 30 L continuous stirred tank reactor. Three bio-H2 release strategies were followed: uncontrolled, intermittent, and constant. In the so called uncontrolled fermentation, without bio-H2 pp control, a bio-H2 molar yield of 1.2 mol/mol glucose was obtained. A sustained low bio-H2 pp of 0.06 atm increased the bio-H2 production rate from 16.1 to 108 mL/L/h with a stable bio-H2 percentage of 55% (v/v) and a molar yield of 1.9 mol/mol glucose. Biogas release enhanced bio-H2 production because lower bio-H2 pp, CO2 concentration, and reduced volatile fatty acids accumulation prevented the associated inhibitions and bio-H2 consumption.

Biohydrogen production based on the evaluation of kinetic parameters of a mixed microbial culture using glucose and fruit-vegetable waste as feedstocks.

Hydrogen (H2) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H2 production obtained were successfully adjusted by a logistic model. The kinetic parameters (µ max = 0.101 h(-1), K s = 2.56 g/L) of an H2-producing microbial culture determined by the Monod and Haldane-Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H2 production of 700 mL was attained. The feasibility of producing H2 from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H2 production and waste organic material degradation was determined. The highest H2 production rate (1.7 mmol/day), the highest cumulative H2 volume (310 mL), and 25 % chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37 g COD/L. The lowest H2 production rates were obtained with relatively low initial substrate concentrations of 5 and 11 g COD/L. The H2 production rates with FVW were also characterized by the logistic model. Similar cumulative H2 production was obtained when glucose and FVW were used as substrates.

Anaerobic digestion and co-digestion processes of vegetable and fruit residues: process and microbial ecology.

This study evaluated the feasibility of methane production from fruit and vegetable waste (FVW) obtained from the central food distribution market in Mexico City using an anaerobic digestion (AD) process. Batch systems showed that pH control and nitrogen addition had significant effects on biogas production, methane yield, and volatile solids (VS) removal from the FVW (0.42 m(biogas)(3)/kg VS, 50%, and 80%, respectively). Co-digestion of the FVW with meat residues (MR) enhanced the process performance and was also evaluated in a 30 L AD system. When the system reached stable operation, its methane yield was 0.25 (m(3)/kg TS), and the removal of the organic matter measured as the total chemical demand (tCOD) was 65%. The microbial population (general Bacteria and Archaea) in the 30 L system was also determined and characterized and was closely correlated with its potential function in the AD system.

H2S and volatile fatty acids elimination by biofiltration: clean-up process for biogas potential use.

In the present work, the main objective was to evaluate a biofiltration system for removing hydrogen sulfide (H(2)S) and volatile fatty acids (VFAs) contained in a gaseous stream from an anaerobic digestor (AD). The elimination of these compounds allowed the potential use of biogas while maintaining the methane (CH(4)) content throughout the process. The biodegradation of H(2)S was determined in the lava rock biofilter under two different empty bed residence times (EBRT). Inlet loadings lower than 200 g/m(3)h at an EBRT of 81 s yielded a complete removal, attaining an elimination capacity (EC) of 142 g/m(3)h, whereas at an EBRT of 31 s, a critical EC of 200 g/m(3)h was reached and the EC obtained exhibited a maximum value of 232 g/m(3)h. For 1500 ppmv of H(2)S, 99% removal was maintained during 90 days and complete biodegradation of VFAs was observed. A recovery of 60% as sulfate was obtained due to the constant excess of O(2) concentration in the system. Acetic and propionic acids as a sole source of carbon were also evaluated in the bioreactor at different inlet loadings (0-120 g/m(3)h) obtaining a complete removal (99%) for both. Microcosms biodegradation experiments conducted with VFAs demonstrated that acetic acid provided the highest biodegradation rate.

Semi-continuous biohydrogen production as an approach to generate electricity.

In this work, a semi-continuous biological system was established to produce hydrogen and generate electricity by coupling the bioreactor to a fuel cell. Heat and acid pretreatments (at 35 and 55 degrees C) of a seed sludge used as inoculum were performed in order to increase hydrogen producers. Different initial glucose concentrations (IGC) were tested for heat pretreated inoculum at 35 degrees C to determine the optimum concentration of glucose that supported the highest hydrogen production. Results showed that the heat pretreated inoculums (35 degrees C) reached the highest hydrogen molar yield of 2.85 mol H(2)/mol glucose (0.014 L/h), which corresponds to the acetic acid pathway. At the optimum IGC (10 g/L, 35 degrees C) the hydrogen molar yield was 3.6 mol H(2)/mol glucose (0.023 L/h). The coupled bioreactor-fuel cell system yielded an output voltage of 1.06 V, power of 0.1 W (25 degrees C) and a current of 68 mA. The overall results suggest that high hydrogen molar yields can be obtained through the acetic acid pathway and that is feasible to generate electricity using hydrogen from the semi-continuous bioreactor.

Toluene biofiltration by the fungus Scedosporium apiospermum TB1.

The performance of biofilters inoculated with the fungus Scedosporium apiospermum was evaluated. This fungus was isolated from a biofilter which operated with toluene for more than 6 months. The experiments were performed in a 2.9 L reactor packed with vermiculite or with vermiculite-granular activated carbon as packing material. The initial moisture content of the support and the inlet concentration of toluene were 70% and 6 g/m3, respectively. As the pressure drop increased from 5-40 mm H2O a strong initial growth was observed. Stable operation was maintained for 20 days with a moisture content of 55% and a biomass of 33 mg biomass/g dry support. These conditions were achieved with intermittent addition of culture medium, which permitted a stable elimination capacity (EC) of 100 g/m3(reactor)h without clogging. Pressure drop across the bed and CO2 production were related to toluene elimination. Measurement of toluene, at different levels of the biofilter, showed that the system attained higher local EC (200 g/m3(r)h) at the reactor outlet. These conditions were related to local humidity conditions. When the mineral medium was added periodically before the EC decreases, EC of approximately 258 g/m3(r)h were maintained with removal efficiencies of 98%. Under these conditions the average moisture content was 60% and 41 mg biomass/g dry support was produced. No sporulation was observed. Evaluation of bacterial content and activities showed that the toluene elimination was only due to S. apiospermum catabolism.