► Methane production under the specific conditions in Mexico City was demonstrated. ► Enhanced performance was achieved with pH control and nitrogen addition. ► Co-digestion of FVW with meat residues ...allows high and stable performance (30L). ► The microbial population in the AD system during optimal performance was determined. ► Bacterial and Archaea populations were correlated with its function in the AD system.
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 (0.42mbiogas3/kgVS, 50%, and 80%, respectively). Co-digestion of the FVW with meat residues (MR) enhanced the process performance and was also evaluated in a 30L AD system. When the system reached stable operation, its methane yield was 0.25 (m3/kgTS), 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 30L system was also determined and characterized and was closely correlated with its potential function in the AD system.
Butyrate is a common fatty acid produced in important fermentative systems, such as the human/animal gut and other H
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 (PH
). 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.
,
, and
were the most abundant phylotypes in the closed system without PH
control, whereas
,
, and
were the most abundant phylotypes under continuous operation at low PH
. Putative butyrate producers identified in our system were from
,
,
, and
. 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.,
), acetate (i.e.,
and
), and lactate producers (i.e.,
and
) took place under continuous-flow operation at low PH
.
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 PH
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.
The co-digestion process of crude cheese whey (CCW) with fruit vegetable waste (FVW) for biohydrogen production was investigated in this study. Five different C/N ratios (7, 17, 21, 31, and 46) were ...tested in 2 L batch systems at a pH of 5.5 and 37 °C. The highest specific biohydrogen production rate of 10.68 mmol H2/Lh and biohydrogen yield of 449.84 mL H2/g COD were determined at a C/N ratio of 21. A pyrosequencing analysis showed that the main microbial population at the initial stage of the co-digestion consisted of Bifidobacterium, with 85.4% of predominance. Hydrogen producing bacteria such as Klebsiella (9.1%), Lactobacillus (0.97%), Citrobacter (0.21%), Enterobacter (0.27%), and Clostridium (0.18%) were less abundant at this culture period. The microbial population structure was correlated with the lactate, acetate, and butyrate profiles obtained. Results demonstrated that the co-digestion of CCW with FVW improves biohydrogen production due to a better nutrient balance and improvement of the system's buffering capacity.
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•Enhanced H2 production with crude cheese whey and fruit and vegetable waste.•Highest H2 production rate and yield at a C/N ratio of 21.•Co-digestion allowed better nutrient balance and buffer capacity.•Bifidobacterium (85.4%) was responsible for syntrophic acid degradation.
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.
•Carotenoids (CD) constitute a very interesting product for many purpose.•Rhodopsuedomas palustris ATCC 1007 produce high specific CD production.•High CD production was obtained under high ammonium ...concentration and low light intensity.•Carotenoids production are regulated by growth and light intensity.•Light intensity has a stronger effect than ammonium concentration on CD production.
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.
Two-stage process of dark fermentation (DF) and photo fermentation (PF), using fruit and vegetable waste (FVW) and cheese whey powder (CWP), was used as an approach to enhance the hydrogen (H2) ...production. FVW and CWP at C/N ratios of 34, 39, 60, 71 and 82 were tested as substrates for DF. Dilution (1:2, 1:5, 1:10) of the DF effluents was used as a coupling strategy. DF effluents with low-butyrate and high lactate concentrations were obtained as a function of an increased C/N ratio, which results in high H2 production during the PF. Maximum overall H2 yields of 793.7 and 695.4 mLH2/gChemical Oxygen Demand (COD) were obtained using a 1:10 dilution, at a C/N ratio of 60 and 70, respectively. These H2 yields were higher than those obtained with the individual processes. The C/N ratio at the DF stage regulate not only H2 production but also the distribution and concentrations of by-products. These metabolites, in turn, control the H2 production during the PF. Predominant microbial population for both processes (DF: C/N = 34 Acetobacter lovaniensis, Clostridium butyricum; C/N = 39 C. butyricum, Enterobacter sp, Bifidobacterium; C/N = 82 Lactobacillus casei; PF: Rhodopseudomonas palustris) were in accordance with the final metabolic products.
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•Enhanced H2 production by dark-photo (DF-PF) fermentations was demonstrated.•Fruit and vegetable waste and cheese whey as substrate allows waste removal and H2 production.•Increased C/N ratio reduces H2 yield at DF, but increase the H2 production at PF.•DF effluents with high lactate concentrations promotes high H2 production at PF.•Microbial population for both DF, PF in accordance with the final metabolic products.
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.
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.
Physiological and metabolic behavior of photoheterotrophic mixed cultures (PHMCs), monocultures of Rhodopseudomonas palustris, Clostridium pasteurianum and Syntrophomonas wolfei and a designed ...microbial consortium (DMC), consisting of these microorganisms that emulates natural consortia were studied. Growing and photoheterotrophic nongrowing conditions to simulate the use of dark fermentative effluents were used. Under growing conditions, C. pasteurianum showed higher bioH2 production (8.5 mmol) and molar bioH2 yield (21 mmoLH2/gCOD), while R. palustris did not produce this gas. Under nongrowing conditions, DMC reached the highest bioH2 production (10 mmol) and bioH2 yield (78.6 mmoLH2/gCOD) together with Poly-hydroxy-alkanoates (PHA), followed for PHMC-C2 (7.5; 59.6) and the monocultures. Higher bioH2 and PHA production of the PHMC and the DMC suggest that these conditions promote the use of nonconventional energy pathways, and interactions among microbial populations that allow for the survival and sustain bioH2 production. This study forms the basis for more in-depth studies of the metabolic behavior of photosynthetic natural and designed cultures.
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•Metabolic behavior of natural and designed photoheterotrophic cultures was evaluated.•Nongrowing conditions promote the highest bioH2 production in microbial consortia.•Microbial interactions allow for the survival and sustain bioH2 production.•BioH2 and PHA production are involved in the metabolic energy conservation.•Feasibility of design a microbial community for high bioH2 production was demonstrated.
The effect of the flux patterns promoted by a reactor's impeller distribution on the biological hydrogen (bioH2) production by a microbial consortium was determined. The flux patterns were analyzed ...and characterized by the application of computational fluid dynamics (CFD, ANSYSS Fluent 14.5). Two different mixing systems; predominantly axial (pitched blade PB4) or radial flow (Rushton) impellers were evaluated. Based on CFD results, four different impeller configurations were experimentally assessed to produce bioH2. The highest bioH2 productivity of 440 mL/Lh was determined with PB4 impellers, under the best configuration. In the second-best configuration, also obtained with the PB4, a bioH2 productivity of 407.94 mL/Lh was measured. The configurations based on Rushton impellers showed lower bioH2 productivity (177.065 mL/Lh average). Therefore, the experiments where the axial pumping was favored showed the highest bioH2 production as a consequence of the enhanced transfer of the bioH2 from the liquid phase to the reactor headspace.
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•Flux patterns were analyzed by CFD in a bio-hydrogen (bioH2) production system.•Experimental observations were successfully compared to CFD results.•PB4 impellers pump fluid efficiently, increasing the bioH2 production.•The mechanism relies on mass transfer phenomena of the bioH2 from the liquid phase.•The hydrodynamic optimization of the reactor enhances the bioH2 production.
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