Elvira Ríos-Leal

Center for Research and Advanced Studies of the National Polytechnic Institute, Ciudad de México, The Federal District, Mexico

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Publications (44)88.97 Total impact

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    ABSTRACT: The use of microalgae in wastewater treatment and its biotechnological exploitation for the production of biofuels is a potential environmental application. Some species of microalgae are notable due to their lipid composition and fatty acid profile suitable for biofuel production. During the present study, a factorial 23 experimental design was conducted, which assessed three factors: i) two species of microalgae (Chlorella vulgaris and Nannochloris oculata), ii) two types of culture media [wastewater of tilapia farming (WTF) and bold’s basal medium (BB)], and iii) two types of lighting (multi-LED lamps and white light). Microalgae were inoculated in photobioreactors in 6 L of medium (WTF or BBM) at an initial concentration of 1.0 × 106 cells ml-1 at 20 ± 2°C. The highest average cell density as well as the highest productivity of biomass observed in the treatments was C. vulgaris treatment in BBM and multi-LED lighting (8.83 × 107 cells ml -1 and 0.0854 g l -1 d -1 , respectively). Although the majority of lipid productivity was obtained in the exponential phase of N. oculata cultivated in multi-LEDs in both treatments (BBM with 58% and WTF with 52%), cultivation of both species was generally maintained in WTF and were those that presented the major lipid productivity (2-18 mg l -1 d -1 ) in comparison with those cultivated in BBM. Palmitic, stearic, oleic, linoleic, linolenic and eicosanoic (C16–C20) fatty acids were present in both species of microalgae in concentrations between 26 and 74%. Based on the results of the present study, we conclude that cultivation of N. oculata and/or C. vulgaris in WTF illuminated with multi-LEDs is an economic and sustainable alternative for biodiesel production because it can represent up to 58% of lipids with a fatty acid profile optimal up to 74% of the total fatty acids.
    AFRICAN JOURNAL OF BIOTECHNOLOGY 05/2015; 14(20):1710-1770. DOI:10.5897/AJB2015.14421 · 0.57 Impact Factor
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    ABSTRACT: The objective of this work was to evaluate the effect of the cathodic catalyst (either chalcogenide or Pt) on bioelectricity production from actual municipal leachate in a microbial fuel cell equipped with an anode made of granular graphite (MFC-G) and seeded with an inoculum enriched in Mn(IV)-reducing bacteria. Each face (I and II) of the MFC-G was characterized by separate (I and II), in series, and parallel connection. Parallel connection of faces increased the maximum volumetric power up to 1239 and 1799 mW m−3 for RuxMoySez and Pt, respectively. In general parallel connection of electrode faces significantly decreased the Rint (44 and 77 Ω for RuxMoySez and Pt, respectively). In the batch operation where the cells were connected to external resistances (Rext) the average volumetric powers PV-ave in the second cycle of batch operation were 1005 ± 5 and 1317 ± 687 mW m−3 whereas organic matter removal efficiencies of 70 and 85% were registered for the RuxMoySez and Pt, respectively. During the repetitive batch operation of the cells loaded with an actual leachate there was preliminary evidence of an in-cell enrichment process. In principle, the MFC with catalyst RuxMoySez exhibited a performance 24% and 20% lower than that with Pt (on PV-ave and organic matter removal basis, respectively). This would point to a trade-off or compromise solution, since the cost of RuxMoySez catalyst is 70% lower than that of Pt.
    International Journal of Hydrogen Energy 10/2014; 39(29):16667–16675. DOI:10.1016/j.ijhydene.2014.05.178 · 2.93 Impact Factor
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    ABSTRACT: Biohydrogen production has been coupled in some cases to other energy production technologies in order to overcome its modest energy gains. Anaerobic digestion, when used for methane recovery, has long been regarded as an energy recovery technology. We determined the energy potential from the coupling of either semi-continuous or batch hydrogen lab-scale bioreactors to a methanogenic stage. All processes were performed in solid substrate fermentation mode using the organic fraction of municipal solid wastes as first fed. Semi-continuous reactors for hydrogen production, operated at 20.9% total solids, 21 d mass retention time and 55 °C, averaged 202 NmL H2/kgrwm/d. In the batch hydrogen stage at 20.9% total solids, 50 h fermentation time and 55 °C, the hydrogen yield was 1200 mmol H2/kgVS and initial hydrogenogenesis rate was 68.3 mmolH2/kgvs/hmmolH2/kgvs/h. The methanogenic stage in semi-continuous performance at 18.4% total solids, 28 d mass retention time and 55 °C produced 2023 NmL CH4/kgrwm/d. Resultant energetic potentials (ÊP) were calculated from the theoretical combustion of the total hydrogen or methane produced by all the substrate fed to the process. ÊP for semi-continuous and batch hydrogenogenesis were 256 and 271 kJ/kgdb, whereas for the methanogenic stage was 11,889 kJ/kgdb. Correspondingly, energetic fluxes (EF) were calculated from the theoretical combustion of the hydrogen or methane productivities. The EF for semi-continuous and batch hydrogenogenesis were 2.55 and 24.1 kJ/kgrwm/d, whereas for the methanogenic stage was 80.3 kJ/kgrwm/d. Indeed, coupling of the methanogenic stage to either semi-continuous or batch hydrogenogenesis increased their energetic potentials by 4600 and 4300%. These results showed the clear advantage of the methanogenesis coupling in order to yield high energetic potentials from wastes.
    International Journal of Hydrogen Energy 10/2014; 39(29):16587–16594. DOI:10.1016/j.ijhydene.2014.06.077 · 2.93 Impact Factor
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    ABSTRACT: Biohydrogen is a sustainable form of energy as it can be produced from organic waste through fermentation processes involving dark fermentation and photofermentation. Very often biohydrogen is included as a part of biorefinery approaches that reclaim organic wastes that are abundant sources of renewable and low cost substrate that can be efficiently fermented by microorganisms. The aim of this work is to critically assess selected bioenergy alternatives from organic solid waste, such as biohydrogen and bioelectricity, and evaluate their relative advantages and disadvantages in the context of biorefineries, and finally indicate the trends for future research and development. Biorefining is the sustainable processing of biomass into a spectrum of marketable products, which means: energy, materials, chemicals, food and feed. Dark fermentation (DF) of organic wastes could be the beach-head of complete biorefineries that generate biohydrogen as a first step and could significantly influence the future of solid waste management. Series systems show a better efficiency than one-stage process regarding substrate conversion to hydrogen and bioenergy. The DF also produces fermented by-products (fatty acids and solvents), so there is an opportunity for further combining with other processes that yield more bioenergy. Photoheterotrophic fermentation (PF) is one of them: photosynthetic heterotrophs such as non sulphur purple bacteria can thrive on the simple organic substances produced in DF and light, to give more H2. Effluents from PF and digestates can be processed in microbial fuel cells for bioelectricity production and methanogenic digestion for methane generation, thus integrating a diverse block of bioenergies. Several digestates from bioenergies could be used for bioproducts generation such as cellulolytic enzymes and saccharification processes leading to ethanol fermentation (another bioenergy), thus completing the inverse cascade. Finally, biohydrogen, biomethane and bioelectricity could contribute to significant improvements for solid organic waste management in agricultural regions, as well as in urban areas.
    Waste Management & Research 05/2014; 32:353-365. · 1.11 Impact Factor
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    ABSTRACT: Biohydrogen is a sustainable form of energy as it can be produced from organic waste through fermentation processes involving dark fermentation and photofermentation. Very often biohydrogen is included as a part of biorefinery approaches, which reclaim organic wastes that are abundant sources of renewable and low cost substrate that can be efficiently fermented by microorganisms. The aim of this work was to critically assess selected bioenergy alternatives from organic solid waste, such as biohydrogen and bioelectricity, to evaluate their relative advantages and disadvantages in the context of biorefineries, and finally to indicate the trends for future research and development. Biorefining is the sustainable processing of biomass into a spectrum of marketable products, which means: energy, materials, chemicals, food and feed. Dark fermentation of organic wastes could be the beach-head of complete biorefineries that generate biohydrogen as a first step and could significantly influence the future of solid waste management. Series systems show a better efficiency than one-stage process regarding substrate conversion to hydrogen and bioenergy. The dark fermentation also produces fermented by-products (fatty acids and solvents), so there is an opportunity for further combining with other processes that yield more bioenergy. Photoheterotrophic fermentation is one of them: photosynthetic heterotrophs, such as non-sulfur purple bacteria, can thrive on the simple organic substances produced in dark fermentation and light, to give more H2. Effluents from photoheterotrophic fermentation and digestates can be processed in microbial fuel cells for bioelectricity production and methanogenic digestion for methane generation, thus integrating a diverse block of bioenergies. Several digestates from bioenergies could be used for bioproducts generation, such as cellulolytic enzymes and saccharification processes, leading to ethanol fermentation (another bioenergy), thus completing the inverse cascade. Finally, biohydrogen, biomethane and bioelectricity could contribute to significant improvements for solid organic waste management in agricultural regions, as well as in urban areas.
    04/2014; 32(5). DOI:10.1177/0734242X14529178
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    ABSTRACT: This work focused on the hydrogen production from the organic fraction of municipal solid waste (OFMSW) in solid substrate fermentation (SSF) with a double purpose: (i) to evaluate the effect of the total solids content (20.9 and 35% TS), temperature (35 and 55 degrees C) and mass retention time (MRT, 21 and 14 d) on semi-continuous fermentation, and (ii) to test the supplementation of OFMSW with nutrient nitrogen in the form of waste activated sludge in batch mini-reactors. Firstly, in the semi-continuous fermentation, it was found that factors had significant influence on hydrogen productivity in the order: total solids > MRT > temperature. Significant interactions amidst factors were only observed between TS x temperature and TS x MRT. Indeed, best hydrogen productivity averaged up to 123 NmL H-2/kg(wmr)/d in reactors fed with 20.9%TS feedstock. In general, variations and inhibition of hydrogen production were related to low pH and lactic acid and solvent deviation of the fermentation. Therefore these parameters should be followed with particular attention in order to implement correction and recovery techniques. Secondly, in the batch fermentation, supplementation with nitrogen (adjusted C/N to 30) did not show a significant effect. Highest results were cumulative hydrogen production = 1641 mu mol(H2)/g VS and initial hydrogen production = 68.3 mu mol(H2)/g VS/h in the mini-reactors without addition of alkalinity or sludge. No significant lag phase was observed in all the experimental units. Higher specific energetic potential (due to biohydrogen) were obtained for batch fermentation units compared with the semi-continuous process (3-fold higher). Copyright
    International Journal of Hydrogen Energy 09/2013; 38(28):12527-12538. DOI:10.1016/j.ijhydene.2013.02.124 · 2.93 Impact Factor
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    ABSTRACT: Hydrogen is a valuable clean energy source, and its production by biological processes is attractive and environmentally sound and friendly. In México 5 million tons/yr of agroindustrial wastes are generated; these residues are rich in fermentable organic matter that can be used for hydrogen production. On the other hand, batch, intermittently vented, solid substrate fermentation of organic waste has attracted interest in the last 10 years. Thus the objective of our work was to determine the effect of initial total solids content and initial pH on H2 production in batch fermentation of a substrate that consisted of a mixture of sugarcane bagasse, pineapple peelings, and waste activated sludge. The experiment was a response surface based on 2(2) factorial with central and axial points with initial TS (15-35%) and initial pH (6.5-7.5) as factors. Fermentation was carried out at 35 °C, with intermittent venting of minireactors and periodic flushing with inert N2 gas. Up to 5 cycles of H2 production were observed; the best treatment in our work showed cumulative H2 productions (ca. 3 mmol H2/gds) with 18% and 6.65 initial TS and pH, respectively. There was a significant effect of TS on production of hydrogen, the latter decreased with initial TS increase from 18% onwards. Cumulative H2 productions achieved in this work were higher than those reported for organic fraction of municipal solid waste (OFMSW) and mixtures of OFMSW and fruit peels waste from fruit juice industry, using the same process. Specific energetic potential due to H2 in our work was attractive and fell in the high side of the range of reported results in the open literature. Batch dark fermentation of agrowastes as practiced in our work could be useful for future biorefineries that generate biohydrogen as a first step and could influence the management of this type of agricultural wastes in México and other countries and regions as well.
    Journal of Environmental Management 05/2013; 128C:126-137. DOI:10.1016/j.jenvman.2013.04.042 · 3.19 Impact Factor
  • Bioremediation and Sustainable Environmental Technologies-2013, Edited by R.R. Sirabian and R.Darlington, 01/2013; Battelle Memorial Institute., ISBN: 978-0-9819730-7-4
  • Bioremediation and Sustainable Environmental Technologies-2013, Edited by R.R. Sirabian and R. Darlington, 01/2013; Battelle Memorial Institute., ISBN: 978-0-9819730-7-4
  • International Journal of Hydrogen Energy 01/2013; 38(28):12527. · 2.93 Impact Factor
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    ABSTRACT: The objective of this study was twofold: (i) to evaluate the effect of co-substrate supplementation and possible synergistic effect of the indigenous population and a lindane-acclimated inoculum on the removal of lindane in three-phase, aerobic slurry bioreactors (SB) , and (ii) to evaluate the effect final electron acceptor (O 2 , CO 2 and SO 4-2 , or A, M, and SR, respectively) and supplementation with carbon source (sucrose, 1 and 0 g/L; C or NC, respectively) on the removal of lindane in triphasic lab scale SB. In a first experiment lindane was significantly removed in the first week of operation (55-70%); its reduction further continued at a lower rate. Both factors had a moderately significant effect; on the one hand, sucrose supplementation enhanced the removal of lindane (p < 0.08); on the other hand the indigenous microflora and lindane-acclimated inoculum exhibited some kind of antagonism (p < 0.07), since removals in SB with sterile soil were higher than those with live soil. In a second experiment, there was a significant effect of factor 'electron acceptors' on removal of lindane (p < 0.0001): lindane removal followed the order A > SR > M. Supplementation with sucrose had a significant positive effect (p < 0.004). Main metabolites from lindane degradation were chlorobenzene (CB), 1,2-dichlorobenzene (1,2-DCB) 1,3-dichlorobenzene (1,3-DCB) and 1,2,4-trichlorobenzene (1,2,4-TCB) in aerobic and sulfate reducing slurry bioreactors, only CB and 1,2-DCB were found in methanogenic units. Metabolites were consistent with those reported in aerobic and anaerobic degradation pathways of lindane.
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    ABSTRACT: The purpose of our study was 2-fold: (i) to evaluate the effect of dominant electron acceptor [either aerobic, methanogenic, or sulfate-reducing slurry bioreactor (SB)] and biostimulation with sucrose on lindane removal from heavy soil and (ii) to assess the effect of the type of combined environments [partially aerated methanogenic (PAM) and simultaneous methanogenic-sulfate reducing (M-SR)] and addition of silicone oil as solvent on lindane removal from a clayish agricultural soil with high levels of organic matter.In the first experiment, the main effect of electron acceptor was significant (pA≫M SBs. On the other hand, co-substrate sucrose was not significant (p=0.67). Yet, the interaction was moderately significant (p
    Journal of Biotechnology 11/2012; 47(11). DOI:10.1016/j.procbio.2011.10.013 · 2.88 Impact Factor
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    ABSTRACT: The purpose of our research was to evaluate the effect of eliminating supplementation of sucrose to the reactor influent on the performance of a lab scale partially-aerated methanogenic fluidized bed bioreactor (PAM-FBBR). Two operational stages were distinguished: in the first stage the influent contained a mixture of 120/30/1000 mg/L of 2,4,6-trichlorophenol/phenol/COD-sucrose (TCP/Phe/COD-sucrose); in the second stage only the xenobiotic concentrations were the same 120/30 mg/L of TCP/Phe whereas sucrose addition was discontinued. Removal efficiencies of TCP, Phe, and COD were very high and close for both stages; i.e., η(TCP): 99.9 and 99.9%; η(Phe): 99.9 and 99.9%; η(COD) = 96.46 and 97.48% for stage 1 and stage 2, respectively. Traces of 2,4,6 dichlorophenol (0.05 mg/L) and 4-chlorophenol (0.07-0.26 mg/L) were found during the first 15 days of operation of the second stage, probably due to the adaptation to no co-substrate conditions. Net increase of chloride anion Cl(-) in effluent ranged between 59.5 and 61.5 mg Cl(-)/L that was very close to the maximum theoretical concentration of 62.8 mg Cl(-)/L. PCR-DGGE analysis revealed a richness decrease of eubacterial domain posterior to sucrose elimination from the influent whereas archaeal richness remained almost the same. However, the bioreactor performance was not negatively affected by discontinuing the addition of co-substrate sucrose. Our results indicate that the application of PAM-FBBR to the treatment of groundwaters polluted with chlorophenols and characterized by the lack of easily degradable co-substrates, is a promising alternative for on site bioremediation.
    Journal of Environmental Management 04/2012; 113. DOI:10.1016/j.jenvman.2012.03.015 · 3.19 Impact Factor
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    ABSTRACT: The scope of this paper encompasses the following subjects: (i) aerobic and anaerobic degradation pathways of γ-hexachlorocyclohexane (HCH); (ii) important genes and enzymes involved in the metabolic pathways of γ-HCH degradation; (iii) the instrumental methods for identifying and quantifying intermediate metabolites, such as gas chromatography coupled to mass spectrometry (GC-MS) and other techniques. It can be concluded that typical anaerobic and aerobic pathways of γ-HCH are well known for a few selected microbial strains, although less is known for anaerobic consortia where the possibility of synergism, antagonism, and mutualism can lead to more particular routes and more effective degradation of γ-HCH. Conversion and removals in the range 39%-100% and 47%-100% have been reported for aerobic and anaerobic cultures, respectively. Most common metabolites reported for aerobic degradation of lindane are γ-pentachlorocyclohexene (γ-PCCH), 2,5-dichlorobenzoquinone (DCBQ), Chlorohydroquinone (CHQ), chlorophenol, and phenol, whereas PCCH, isomers of trichlorobenzene (TCB), chlorobenzene, and benzene are the most typical metabolites found in anaerobic pathways. Enzyme and genetic characterization of the involved molecular mechanisms are in their early infancy; more work is needed to elucidate them in the future. Advances have been made on identification of enzymes of Sphingomonas paucimobilis where the gene LinB codifies for the enzyme haloalkane dehalogenase that acts on 1,3,4,6-tetrachloro 1,4-cyclohexadiene, thus debottlenecking the pathway. Other more common enzymes such as phenol hydroxylase, catechol 1,2-dioxygenase, catechol 2,3-dioxygenase are also involved since they attack intermediate metabolites of lindane such as catechol and less substituted chlorophenols. Chromatography coupled to mass spectrometric detector, especially GC-MS, is the most used technique for resolving for γ-HCH metabolites, although there is an increased participation of HPLC-MS methods. Scintillation methods are very useful to assess final degradation of γ-HCH.
    Journal of Environmental Management 03/2012; 95 Suppl:S306-18. DOI:10.1016/j.jenvman.2011.06.047 · 3.19 Impact Factor
  • Environmental engineering and management journal 01/2012; 11(3):S82. · 1.26 Impact Factor
  • Environmental engineering and management journal 01/2012; 11:S82. · 1.26 Impact Factor
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    ABSTRACT: The objective of this study was two-fold: (i) to evaluate the effect of co-substrate supplementation and possible synergistic effect of the indigenous population and a lindane-acclimated inoculum on the removal of lindane in three-phase, aerobic slurry bioreactors (SB) , and (ii) to evaluate the effect final electron acceptor (O2, CO2 and SO4 -2, or A, M, and SR, respectively) and supplementation with carbon source (sucrose, 1 and 0 g/L; C or NC, respectively) on the removal of lindane in triphasic lab scale SB. In a first experiment lindane was significantly removed in the first week of operation (55-70%); its reduction further continued at a lower rate. Both factors had a moderately significant effect; on the one hand, sucrose supplementation enhanced the removal of lindane (p < 0.08); on the other hand the indigenous microflora and lindane-acclimated inoculum exhibited some kind of antagonism (p < 0.07), since removals in SB with sterile soil were higher than those with live soil. In a second experiment, there was a significant effect of factor ‘electron acceptors’ on removal of lindane (p < 0.0001): lindane removal followed the order A > SR > M. Supplementation with sucrose had a significant positive effect (p < 0.004). Main metabolites from lindane degradation were chlorobenzene (CB), 1,2-dichlorobenzene (1,2-DCB) 1,3-dichlorobenzene (1,3-DCB) and 1,2,4- trichlorobenzene (1,2,4-TCB) in aerobic and sulfate reducing slurry bioreactors, only CB and 1,2-DCB were found in methanogenic units. Metabolites were consistent with those reported in aerobic and anaerobic degradation pathways of lindane
    Environmental engineering and management journal 01/2012; 11(10). · 1.26 Impact Factor
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    ABSTRACT: In the first batch solid substrate anaerobic hydrogenogenic fermentation with intermittent venting (SSAHF-IV) of the organic fraction of municipal solid waste (OFMSW), a cumulative production of 16.6 mmol H(2)/reactor was obtained. Releases of hydrogen partial pressure first by intermittent venting and afterward by flushing headspace of reactors with inert gas N(2) allowed for further hydrogen production in a second to fourth incubation cycle, with no new inoculum nor substrate nor inhibitor added. After the fourth cycle, no more H(2) could be harvested. Interestingly, accumulated hydrogen in 4 cycles was 100% higher than that produced in the first cycle alone. At the end of incubation, partial pressure of H(2) was near zero whereas high concentrations of organic acids and solvents remained in the spent solids. So, since approximate mass balances indicated that there was still a moderate amount of biodegradable matter in the spent solids we hypothesized that the organic metabolites imposed some kind of inhibition on further fermentation of digestates. Spent solids were washed to eliminate organic metabolites and they were used in a second SSAHF-IV. Two more cycles of H(2) production were obtained, with a cumulative production of ca. 2.4 mmol H(2)/mini-reactor. As a conclusion, washing of spent solids of a previous SSAHF-IV allowed for an increase of hydrogen production by 15% in a second run of SSAHF-IV, leading to the validation of our hypothesis.
    Journal of Environmental Management 02/2011; 95 Suppl:S355-9. DOI:10.1016/j.jenvman.2011.01.017 · 3.19 Impact Factor
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    Journal of Biotechnology 11/2010; 150:561-562. DOI:10.1016/j.jbiotec.2010.10.023 · 2.88 Impact Factor
  • Journal of Biotechnology 11/2010; 150:145-146. DOI:10.1016/j.jbiotec.2010.08.378 · 2.88 Impact Factor