GTA - Artículos de revista https://uvadoc.uva.es/handle/10324/31061 2026-04-25T12:22:15Z 2026-04-25T12:22:15Z Bordel Velasco, Sergio Rodríguez, Elisa Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/35167 2025-03-26T19:10:02Z 2018-01-01T00:00:00Z

Polyhydroxyalkanoates (PHAs) are biodegradable plastics that can be produced by some methanotrophic organisms such as those of the genus Methylocystis. This allows the conversion of a detrimental greenhouse gas into an environmentally friendly high added‐value bioproduct. This study presents the genome sequence of Methylocystis hirsuta CSC1 (a high yield PHB producer). The genome comprises 4,213,043 bp in 4 contigs, with the largest contig being 3,776,027 bp long. Two of the other contigs are likely to correspond to large size plasmids. A total of 4,664 coding sequences were annotated, revealing a PHA production cluster, two distinct particulate methane monooxygenases with active catalytic sites, as well as a nitrogen fixation operon and a partial denitrification pathway.

2018-01-01T00:00:00Z Muñoz Torre, Raúl Soto Guzmán, Marvelia Cenit Zúñiga, Cristal Revah, Sergio https://uvadoc.uva.es/handle/10324/35165 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

This study aimed at systematically comparing the potential of two empirical methods for the estimation of the volumetric CH4 mass transfer coefficient (klaCH4), namely gassing-out and oxygen transfer rate (OTR), to describe CH4 biodegradation in a fermenter operated with a methanotrophic consortium at 400, 600 and 800 rpm. The klaCH4 estimated from the OTR methodology accurately predicted the CH4 elimination capacity (EC) under CH4 mass transfer limiting conditions regardless of the stirring rate (∼9% of average error between empirical and estimated ECs). Thus, empirical CH4-ECs of 37.8 ± 5.8, 42.5 ± 5.4 and 62.3 ± 5.2 g CH4 m−3 h−1 vs predicted CH4-ECs of 35.6 ± 2.2, 50.1 ± 2.3 and 59.6 ± 3.4 g CH4 m−3 h−1 were recorded at 400, 600 and 800 rpm, respectively. The rapid Co2+-catalyzed reaction of O2 with SO3−2 in the vicinity of the gas-liquid interphase during OTR determinations, mimicking microbial CH4 uptake in the biotic experiments, was central to accurately describe the klaCH4.

2018-01-01T00:00:00Z Rodríguez Rodríguez, Elisa López Alonso, Juan Carlos Prieto Ferrero, Patricia Merchán Catalina, Laura García Encina, Pedro Antonio Lebrero Fernández, Raquel Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/35164 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

The ability of methanotrophs to rapidly respond to intentional or accidental stress conditions caused by operational failures or process fluctuations is of utmost importance to guarantee the robustness of CH4 abatement biotechnologies. In this study, the performance of a continuous and two feast-famine (5:5 days feast-famine cycles) stirred tank reactors treating diluted CH4 emissions (4–5% v/v) was comparatively assessed for 149 days. The robustness of the three bioreactors towards a 5 days CH4 deprivation episode was thoroughly evaluated at a molecular level (pmoA gene expression level) and correlated to macroscopic process performance. The bioreactors recovered their steady-state abatement performance (in terms of CH4 elimination capacity and CO2 production rate) within 1.5–2 h following CH4 supply resumption concomitantly with a maximum in pmoA gene expression, regardless of the previous operational mode. However, while methanotrophs from the continuous unit maintained higher basal levels of pmoA expression as a strategy for a rapid CH4 metabolism initiation, the strategy of the feast-famine adapted-methanotrophs consisted on a more accurate regulation of their pmoA transcripts levels along with a higher and/or more rapid induction of the pmoA gene by CH4 availability.

2018-01-01T00:00:00Z Cantera Ruiz De Pellon, Sara Sánchez Andrea, Irene Sadornil Delgado, Lidia Jimena García Encina, Pedro Antonio Stams, Alfons J.M. Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/35163 2025-03-26T19:10:03Z 2019-01-01T00:00:00Z

Methane bioconversion into products with a high market value, such as ectoine or hydroxyectoine, can be optimized via isolation of more efficient novel methanotrophic bacteria. The research here presented focused on the enrichment of methanotrophic consortia able to co-produce different ectoines during CH4 metabolism. Four different enrichments (Cow3, Slu3, Cow6 and Slu6) were carried out in basal media supplemented with 3 and 6% NaCl, and using methane as the sole carbon and energy source. The highest ectoine accumulation (∼20 mg ectoine g biomass−1) was recorded in the two consortia enriched at 6% NaCl (Cow6 and Slu6). Moreover, hydroxyectoine was detected for the first time using methane as a feedstock in Cow6 and Slu6 (∼5 mg g biomass−1). The majority of the haloalkaliphilic bacteria identified by 16S rRNA community profiling in both consortia have not been previously described as methanotrophs. From these enrichments, two novel strains (representing novel species) capable of using methane as the sole carbon and energy source were isolated: Alishewanella sp. strain RM1 and Halomonas sp. strain PGE1. Halomonas sp. strain PGE1 showed higher ectoine yields (70–92 mg ectoine g biomass−1) than those previously described for other methanotrophs under continuous cultivation mode (∼37–70 mg ectoine g biomass−1). The results here obtained highlight the potential of isolating novel methanotrophs in order to boost the competitiveness of industrial CH4-based ectoine production.

2019-01-01T00:00:00Z Cantera Ruiz De Pellon, Sara Bordel Velasco, Sergio Lebrero Fernández, Raquel Gancedo Verdejo, Juan García Encina, Pedro Antonio Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/35162 2025-03-26T19:10:03Z 2019-01-01T00:00:00Z

Despite the environmental relevance of CH4 and forthcoming stricter regulations, the development of cost-efficient and environmentally friendly technologies for CH4 abatement is still limited. To date, one of the most promising solutions for the mitigation of this important GHG consists of the bioconversion of CH4 into bioproducts with a high profit margin. In this context, methanotrophs have been already proven as cell-factories of some of the most expensive products synthesized by microorganisms. In the case of ectoine (1000 $ kg−1), already described methanotrophic genera such as Methylomicrobium can accumulate up to 20% (ectoine wt−1) using methane as the only carbon source. Moreover, α-methanotrophs, such as Methylosynus and Methylocystis, are able to store bioplastic concentrations up to 50–60% of their total cell content. More than that, methanotrophs are one of the greatest potential producers of methanol and exopolysaccharides. Although this methanotrophic factory could be enhanced throughout metabolic engineering, the valorization of CH4 into valuable metabolites has been already consistently demonstrated under continuous and discontinuous mode, producing more than one compound in the same bioprocess, and using both, single strains and specific consortia. This review states the state-of-the-art of this innovative biotechnological platform by assessing its potential and current limitations.

2019-01-01T00:00:00Z Cantera Ruiz De Pellon, Sara Sánchez Andrea, Irene Lebrero Fernández, Raquel García Encina, Pedro Antonio Stams, Alfons J.M. Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/35160 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

This study constitutes the first-proof-of-concept of a methane biorefinery based on the multi-production of high profit margin substances (ectoine, hydroxyectoine, polyhydroxyalkanoates (PHAs) and exopolysaccharides (EPS)) using methane as the sole carbon and energy source. Two bubble column bioreactors were operated under different magnesium concentrations (0.2, 0.02 and 0.002 g L−1) to validate and optimize this innovative strategy for valorization of CH4 emissions. High Mg2+ concentrations promoted the accumulation of ectoine (79.7–94.2 mg g biomass−1), together with high hydroxyectoine yields (up to 13 mg g biomass−1) and EPS concentrations (up to 2.6 g L culture broth−1). Unfortunately, PHA synthesis was almost negligible (14.3 mg L−1) and only found at the lowest Mg2+ concentration tested. Halomonas, Marinobacter, Methylophaga and Methylomicrobium, previously described as ectoine producers, were dominant in both bioreactors, Methylomicrobium being the only described methanotroph. This study encourages further research on CH4 biorefineries capable of creating value out of GHG mitigation.

2018-01-01T00:00:00Z Franco Morgado, Mariana Toledo Cervantes, Alma González Sánchez, Armando Lebrero Fernández, Raquel Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/31050 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

The performance of a pilot high rate algal pond (HRAP) interconnected with a biogas absorption column during the simultaneous upgrading of biogas and treatment of digestate was evaluated under two innovative biogas and nutrient supply strategies. Process operation with biogas supply during the night at a liquid recirculation/biogas ratio of 0.5 to prevent N2 and O2 stripping resulted in a biomethane complying with most international regulations for injection into natural gas grids (99.1 ± 1% CH4, 0.5 ± 0.2% CO2, 0.6 ± 0.5% N2 and 0.07 ± 0.08% O2). The potential of this technology to remove methyl mercaptan (MeSH), toluene and hexane from biogas (typically present at trace levels) was assessed, for the first time, with removal efficiencies under steady-state correlating with pollutant hydrophobicity (7 ± 7% for hexane, 66 ± 4% for MeSH and 98 ± 1% for toluene). Finally, the supply of digestate during the dark period shifted both microalgae population structure and biomass composition in the HRAP without a significant impact on biomethane quality. Overall, the removal of nitrogen and phosphorous from digestate in the HRAP was almost complete (96–99%) regardless of the nutrient supply strategy.

2018-01-01T00:00:00Z García Pérez, Teresa López Alonso, Juan Carlos Passos, Fabiana Lebrero Fernández, Raquel Revah, Sergio Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/30104 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

The limited gas–liquid mass transfer represents the main challenge in the operation of cost-effective bioreactors devoted to the treatment of poorly soluble gas pollutants such as methane (CH4). This study evaluates the influence of internal gas-recycling strategies on the enhancement of CH4 abatement in a bubble column bioreactor inoculated with the methanotroph Methylocystis hirsuta. Maximum CH4 removal efficiencies of 72.9 ± 0.5% (corresponding to elimination capacities of 35.2 ± 0.4 g m−3 h−1) were recorded under process operation at an empty bed residence time of 30 min and 0.50 m3gas m−3reactor min−1 of internal gas-recycling rate. The accumulation of poly-3-hydroxybutyrate (PHB) in M. hirsuta was evaluated batchwise under limitations of potassium, manganese, nitrogen, and nitrogen with excess of iron. Nitrogen starvation resulted in the highest PHB content (28 ± 1%). Likewise, the implementation of sequential N starvation cycles in a continuous bubble column reactor operated at a gas residence time of 30 min and an internal gas-recycling rate of 0.50 m3gas m−3reactor min−1 supported a PHB content of up to 34.6 ± 2.5%, with a volumetric PHB productivity of 1.4 ± 0.4 kg m−3 d−1 and elimination capacities of 16.2 ± 9.5 g m−3 h−1.

2018-01-01T00:00:00Z López Alonso, Juan Carlos Arnáiz, Esther Merchán Catalina, Laura Lebrero Fernández, Raquel Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/30103 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

The potential of biogas (with and without H2S) and volatile fatty acids (VFAs) to support microbial growth and accumulation of polyhydroxyalkanoates (PHAs) in type II methanotrophs was evaluated batchwise under aerobic conditions. Methylocystis hirsuta was able to grow on artificial biogas (70% CH4, 29.5% CO2, 0.5% H2S) and accumulate PHA up to 45 ± 1% (wt.%) under N-limited conditions. The presence of CO2 and H2S did not significantly influence the growth and PHA synthesis in M. hirsuta compared to control tests provided with pure CH4 at similar concentrations. Likewise, the addition of VFAs to the cultivation broth at initial concentrations of 100–200 mg L−1 did not hamper the growth of this strain on artificial biogas. Indeed, the addition of 10% extra carbon in the form of individual VFAs resulted in an increase in the maximum PHA yield and final PHA content up to 0.45–0.63 gPHA gSubstrate 1 and 48–54% (wt.%), respectively, at the expense of a higher energy demand. Valeric acid supplementation supported the highest 3-hydroxyvalerate content (13.5%) within the biocomposite. In this context, this study demonstrated for the first time that 3-hydroxyvalerate synthesis by M. hirsuta did not depend on CH4 assimilation.

2018-01-01T00:00:00Z Cantera Ruiz De Pellon, Sara Muñoz Torre, Raúl Lebrero Fernández, Raquel López Alonso, Juan Carlos Rodríguez Muñoz, Yadira García Encina, Pedro Antonio https://uvadoc.uva.es/handle/10324/30102 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

Methane, with a global warming potential twenty five times higher than that of CO2 is the second most important greenhouse gas emitted nowadays. Its bioconversion into microbial molecules with a high retail value in the industry offers a potential cost-efficient and environmentally friendly solution for mitigating anthropogenic diluted CH4-laden streams. Methane bio-refinery for the production of different compounds such as ectoine, feed proteins, biofuels, bioplastics and polysaccharides, apart from new bioproducts characteristic of methanotrophic bacteria, has been recently tested in discontinuous and continuous bioreactors with promising results. This review constitutes a critical discussion about the state-of-the-art of the potential and research niches of biotechnologies applied in a CH4 biorefinery approach.

2018-01-01T00:00:00Z Toledo Cervantes, Alma Morales, Tamara González, Álvaro Muñoz Torre, Raúl Lebrero Fernández, Raquel https://uvadoc.uva.es/handle/10324/30064 2025-03-26T19:10:04Z 2018-01-01T00:00:00Z

The long-term performance of a tubular photobioreactor interconnected to a gas absorption column for the abatement of CO2 from biogas and flue-gas was investigated. Additionally, a novel nitrogen feast-famine regime was implemented during the flue-gas feeding stage in order to promote the continuous storage of highly-energetic compounds. Results showed effective CO2 (~98%) and H2S (~99%) removals from synthetic biogas, supported by the high photosynthetic activity of microalgae which resulted in an alkaline pH (~10). In addition, CO2 removals of 99 and 91% were observed during the flue-gas operation depending on the nutrients source: mineral salt medium and digestate, respectively. A biomass productivity of ~8 g m−2 d−1 was obtained during both stages, with a complete nitrogen and carbon recovery from the cultivation broth. Moreover, the strategy of feeding nutrients during the dark period promoted the continuous accumulation of carbohydrates, their concentration increasing from 22% under normal nutrition up to 37% during the feast-famine cycle. This represents a productivity of ~3 g-carbohydrates m−2 d−1, which can be further valorized to contribute to the economic sustainability of the photosynthetic CO2 removal process.

2018-01-01T00:00:00Z Marín de Jesús, David Fernando Posadas Olmos, Esther Cano, Patricia Pérez Martínez, Victor Lebrero Fernández, Raquel Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/30051 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

The influence of the daily and seasonal variations of environmental conditions on the quality of the upgraded biogas was evaluated in an outdoors pilot scale high rate algal pond (HRAP) interconnected to an external absorption column (AC) via a conical settler. The high alkalinity in the cultivation broth resulted in a constant biomethane composition during the day regardless of the monitored month, while the high algal-bacterial activity during spring and summer boosted a superior biomethane quality. CO2 concentrations in the upgraded biogas ranged from 0.1% in May to 11.6% in December, while a complete H2S removal was always achieved regardless of the month. A limited N2 and O2 stripping from the scrubbing cultivation broth was recorded in the upgraded biogas at a recycling liquid/biogas ratio in the AC of 1. Finally, CH4 concentration in the upgraded biogas ranged from 85.6% in December to 99.6% in August.

2018-01-01T00:00:00Z Marín, David Posadas Olmos, Esther Cano, Patricia Pérez Martínez, Victor Blanco, Saúl Lebrero Fernández, Raquel Muñoz Torre, Raúl https://uvadoc.uva.es/handle/10324/30050 2025-03-26T19:10:03Z 2018-01-01T00:00:00Z

The yearly variations of the quality of the upgraded biogas and the efficiency of digestate treatment were evaluated in an outdoors pilot scale high rate algal pond (HRAP) interconnected to an external absorption column (AC) via a conical settler. CO2 concentrations in the upgraded biogas ranged from 0.7% in August to 11.9% in December, while a complete H2S removal was achieved regardless of the operational month. CH4 concentrations ranged from 85.2% in December to 97.9% in June, with a limited O2 and N2 stripping in the upgraded biogas mediated by the low recycling liquid/biogas ratio in the AC. Biomass productivity ranged from 0.0 g m−2 d−1 in winter to 22.5 g m−2 d−1 in summer. Finally, microalgae diversity was severely reduced throughout the year likely due to the increasing salinity in the cultivation broth of the HRAP induced by process operation in the absence of effluent.

2018-01-01T00:00:00Z Saavedra Concha, Ricardo Muñoz Torre, Raúl Taboada Meneses, María Elisa Vega Alegre, María del Sol Bolado Rodríguez, Silvia https://uvadoc.uva.es/handle/10324/30032 2025-02-21T11:07:40Z 2018-01-01T00:00:00Z

This work represents a comparative uptake study of the toxic elements arsenic, boron, copper, manganese and zinc in monometallic and multimetallic solutions by four green microalgae species (Chlamydomonas reinhardtii, Chlorella vulgaris, Scenedesmus almeriensis and an indigenous Chlorophyceae spp.), evaluating the effect of pH and contact time. Maximum removal efficiencies for each toxic element were 99.4% for Mn (C. vulgaris, pH 7.0, 3h), 91.9% for Zn (Chlorophyceae spp., pH 5.5, 3h), 88% for Cu (Chlorophyceae spp., pH 7.0, 10 min), 40.7% for As (S. almeriensis, pH 9.5, 3h) and 38.6% for B (S. almeriensis, pH 5.5, 10 min). B removal efficiencies decreased remarkably in multimetallic solutions (down to 0.2% in C. reinhardtii), except for Chlorophyceae spp., the only species isolated from a polluted environment. FTIR spectra shown the highest interactions for As (1150-1300 cm-1) and Cu (3300, 1741, 1535, 1350-1400 cm-1). Results confirms microalgae biomass as a potential biosorbent for toxic elements.

2018-01-01T00:00:00Z Lorenzo Hernando, Ana María Martín Juarez, Judit Bolado Rodríguez, Silvia https://uvadoc.uva.es/handle/10324/29163 2025-02-20T10:13:27Z 2018-01-01T00:00:00Z

Steam explosion (150 – 200 ºC, 5 – 30 min) was performed on a commercial cellulose presented in two configurations (fiberized and compact sheet) and its effect on their chemical and physical properties was studied, along with the influence of two different preservation methods (acetone drying and freezing) after pretreatment. No degradation compounds were produced during pretreatment, although solid recovery (RS) decreased with temperature from 90% to 62%. Similar particle size and surface conditions (increased porosity) were found for both types of pretreated samples despite the extremely different initial configuration. Crystallinity diminished for 150 ºC samples, but 200 ºC pretreatment promoted recrystallization. Pretreatment also reduced polymerization degree, although enzymatic accessibility did not improve. Both acetone and freezing processes extremely affected cellulose properties. Acetone drying counterbalanced crystallinity and enzymatic accessibility variations of pretreated samples, while decreasing polymerization degree to 302. Freezing dramatically decreased enzymatic accessibility of pretreated samples down to 15.8%.

2018-01-01T00:00:00Z Martín Juarez, Judit Riol Pastor, Elena Fernández Sevilla, Jose María Muñoz Torre, Raúl García Encina, Pedro Antonio Bolado Rodríguez, Silvia https://uvadoc.uva.es/handle/10324/28604 2025-05-07T09:27:05Z 2018-01-01T00:00:00Z

Methane production from pretreated and raw mixed microalgae biomass grown in pig manure was evaluated. Acid and basic pretreatments provided the highest volatile solids solubilisation (up to 81%) followed by alkaline-peroxide and ultrasounds (23%). Bead milling and steam explosion remarkably increased the methane production rate, although the highest yield (377 mL CH4/g SV) was achieved by alkali pretreatment. Nevertheless, some pretreatments inhibited biogas production and resulted in lag phases of 7-9 days. Hence, experiments using only the pretreated solid phase were performed, which resulted in a decrease in the lag phase to 2-3 days for the alkali pretreatment and slightly increased biomass biodegradability of few samples. The limiting step during the BMP test (hydrolysis or microbial inhibition) for each pretreatment was elucidated using the goodness of fitting to a first order or a Gompertz model. Finally, the use of digestate as biofertilizer was evaluated applying a biorefinery concept.

2018-01-01T00:00:00Z