Abstract

This work shows the potential of a new way of co-treatment of domestic wastewater (DWW) and a liquid stream coming from the thermal hydrolysis of the organic fraction of municipal solid waste (OFMSW) mediated by a mixed culture of purple phototrophic bacteria (PPB) capable of assimilating carbon and nutrients from the medium. The biological system is an open single-step process operated under microaerophilic conditions at an oxidative reduction potential (ORP) < 0 mV with a photoperiod of 12/24 h and fed during the light stage only so the results can be extrapolated to outdoor open pond operations by monitoring the ORP. The effluent mostly complies with the discharge values of the Spanish legislation in COD and p-values (<125 mg/L; <2 mg/L), respectively, and punctually on values in N (<15 mg/L). Applying an HRT of 3 d and a ratio of 100:7 (COD:N), the presence of PPB in the mixed culture surpassed 50% of 16S rRNA gene copies, removing 78% of COD, 53% of N, and 66% of P. Furthermore, by increasing the HRT to 5 d, removal efficiencies of 83% of COD, 65% of N, and 91% of P were achieved. In addition, the reactors were further operated in a membrane bioreactor, thus separating the HRT from the SRT to increase the specific loading rate. Very satisfactory removal efficiencies were achieved by applying an HRT and SRT of 2.3 and 3 d, respectively: 84% of COD, 49% of N, and 93% of P despite the low presence of PPB due to more oxidative conditions, which step-by-step re-colonized the mixed culture until reaching >20% of 16S rRNA gene copies after 49 d of operation. These results open the door to scaling up the process in open photobioreactors capable of treating urban wastewater and municipal solid waste in a single stage and under microaerophilic conditions by controlling the ORP of the system.

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The 7th DEEP PURPLE publication was received on 26 January 2022, revised on 29 June 2022, accepted on 2 August 2022, and published in the Elsevier Journal “Journal of Cleaner Production” Volume 369 on 1 October 2022. The author team (see below in cite and share) is from the Institute of Sustainable Processes, University of Valladolid, Department of Chemical Engineering and Environmental Technology, and Activatec Ltd.

Abstract:

The utilization of methanotrophic haloalkaliphilic bacteria for the production of ectoine in waste treatment plants has demonstrated a great potential to upgrade the traditional use of biogas as energy vector and the current industrial routes for the production of this high added-value chemical (600–1000 €·kg−1). However, the influence of socio-economic aspects such as the location of the plant, the economy of scale and the market fluctuations on the profitability of the process remains unknown. A techno-economic and sensitivity analysis of the bioconversion of CH4 into ectoine in a bubble column bioreactor and the extraction and purification of ectoine via ionic exchange chromatography was herein conducted using Madrid as base-case scenario. The geographical assessment performed in 13 representative cities revealed high differences in the ectoine production costs, ranging from 158 to 231 €·kg−1. The economy of scale analysis evidenced a high dependence of the ectoine production costs towards the production scale, amounting to 782 and 164 €·kg−1 when manufacturing 0.1 and 89.6 t ectoine·y−1, respectively. The techno-economic study also showed a high robustness of CH4-ectoine profitability towards future market fluctuations, with all the scenarios analyzed guaranteeing internal rates of return >15% and payback periods <10 y. Finally, the sensitivity analysis identified the improvement of CH4 elimination capacity in bioreactors, the development of highly efficient microbial strains and the selection of the highest quality ionic exchange resins as key factors impacting the profitability of future biogas-to-ectoine biorefineries.

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Pérez V, Moltó J.L, Lebrero R, Muñoz R (2022) Ectoine production from biogas: a sensitivity analysis. Effect of local commodity prices, economy of scale, market trends and biotechnological limitations. Journal of Cleaner Production ,Elsevier Ltd, 369(133440).

This paper can be accessed here.

Abstract
The application of biogas as a low-priced substrate for the production of ectoines constitutes an opportunity to decrease their production costs and to enhance the viability of anaerobic digestion. The influence of operational conditions on CH4-biogas biodegradation and on ectoines production yields was assessed in continuous pilot bubble column bioreactors. The rise in biomass concentration from 1 to 3 g L−1 resulted in a decrease in the specific ectoine content from 42 ± 8 to 30 ± 4 mgectoine gVSS−1. The concentration of Cu2+ and Mg2+ did not impact process performance, while the use of ammonium as N source resulted in low CH4 biodegradation and ectoine yields (13 ± 7 mgectoine gVSS−1). The increase in CH4 content from 4.5 to 9 %v·v−1 enhanced CH4 removal efficiency. Process operation at NaCl concentrations of 3 %w·w−1 instead of 6 %w·w−1 decreased the ectoine yield to 17 mgectoine gVSS−1. Finally, Methylomicrobium buryatense was identified as the dominant species.

Highlights
• Low biomass concentrations resulted in an increase in the ectoines yields.
• The increase in Cu2+ and Mg2+ concentrations did not enhance ectoines synthesis.
• The use of ammonium instead of nitrate as N source induced biomass decay.
• The increase in CH4 concentration did not enhance ectoines yields.
• Low NaCl concentrations enhanced CH4 biodegradation but reduced ectoines yields.

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María del Rosario Rodero, Raquel Herrero-Lobo, Víctor Pérez, Raúl Muñoz,
Influence of operational conditions on the performance of biogas bioconversion into ectoines in pilot bubble column bioreactors, Bioresource Technology, Volume 358, 2022, 127398, ISSN 0960-8524, https://doi.org/10.1016/j.biortech.2022.127398.

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(https://www.sciencedirect.com/science/article/pii/S0960852422007271)

KEYWORDS: Biogas; Bubble column bioreactor; Ectoine; Hydroxyectoine; Methanotrophs

The 5th DEEP PURPLE Publication was received 5 October 2021, revised 9 December 2021 and published on 15 December 2021 in ACS Sustainable Chemistry & Engineering 2021 Dec 27; 9(51): 17371–17380. The author team (see below in cite and share) is from the Institute of Sustainable Processes, University of Valladolid, Department of Chemical Engineering and Environmental Technology and Activatec Ltd.

Abstract
The capacity of haloalkaliphilic methanotrophic bacteria to synthesize ectoine from CH4-biogas represents an opportunity for waste treatment plants to improve their economic revenues and align their processes to the incoming circular economy directives. A techno-economic and sensitivity analysis for the bioconversion of biogas into 10 t ectoine·y–1 was conducted in two stages: (I) bioconversion of CH4 into ectoine in a bubble column bioreactor and (II) ectoine purification via ion exchange chromatography. The techno-economic analysis showed high investment (4.2 M€) and operational costs (1.4 M€·y–1). However, the high margin between the ectoine market value (600–1000 €·kg–1) and the estimated ectoine production costs (214 €·kg–1) resulted in a high profitability for the process, with a net present value evaluated at 20 years (NPV20) of 33.6 M€. The cost sensitivity analysis conducted revealed a great influence of equipment and consumable costs on the ectoine production costs. In contrast to alternative biogas valorization into heat and electricity or into low added-value bioproducts, biogas bioconversion into ectoine exhibited high robustness toward changes in energy, water, transportation, and labor costs. The worst- and best-case scenarios evaluated showed ectoine break-even prices ranging from 158 to 275 €·kg–1, ∼3–6 times lower than the current industrial ectoine market value.

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Pérez, V., Moltó, J. L., Lebrero, R., & Muñoz, R. (2021). Ectoine Production from Biogas in Waste Treatment Facilities: A Techno-Economic and Sensitivity Analysis. ACS sustainable chemistry & engineering, 9(51), 17371–17380. https://doi.org/10.1021/acssuschemeng.1c06772

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doi: 10.1021/acssuschemeng.1c06772

KEYWORDS: Biogas valorization, Biorefinery, Ectoine, Haloalkaliphilic, methanotrophic bacteria, Techno-economic assessment, Sensitivity analysis

Abstract:

Anaerobic digestion (AD) is a robust biotechnology for the valorisation of organic waste into biogas. However, the rapid decrease in renewable electricity prices requires alternative uses of biogas. In this context, the engineering of innovative platforms for the bio-production of chemicals from CH4 has recently emerged. The extremolyte and osmoprotectant ectoine, with a market price of ~1000€/Kg, is the industrial flagship of CH4-based bio-chemicals. This work aimed at optimizing the accumulation of ectoines using mixed microbial consortia enriched from saline environments (a salt lagoon and a salt river) and activated sludge, and biogas as feedstock. The influence of NaCl (0, 3, 6, 9 and 12 %) and Na2WO4 (0, 35 and 70 μg L−1) concentrations and incubation temperature (15, 25 and 35 °C) on the stoichiometry and kinetics of the methanotrophic consortia was investigated. Consortia enriched from activated sludge at 15 °C accumulated the highest yields of ectoine and hydroxyectoine at 6 % NaCl (105.0 ± 27.2 and 24.2 ± 5.4 mgextremolyte gbiomass−1, respectively). The consortia enriched from the salt lagoon accumulated the highest yield of ectoine and hydroxyectoine at 9 % NaCl (56.6 ± 2.5 and 51.0 ± 2.0 mgextremolyte gbiomass−1, respectively) at 25 °C. The supplementation of tungsten to the cultivation medium did not impact on the accumulation of ectoines in any of the consortia. A molecular characterization of the enrichments revealed a relative abundance of ectoine-accumulating methanotrophs of 7–16 %, with Methylomicrobium buryatense and Methylomicrobium japanense as the main players in the bioconversion of methane into ectoine.

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Alessandro A. Carmona-Martínez, Eva Marcos-Rodrigo, Sergio Bordel, David Marín, Raquel Herrero-Lobo ,Pedro A. García-Encina, Raúl Muñoz, Elucidating the key environmental parameters during the production of ectoines from biogas by mixed methanotrophic consortia, Journal of Environmental Management, Elsevier, Volume 298, 15 November 2021, 113462

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https://doi.org/10.1016/j.jenvman.2021.113462

Received 27 November 2020, Revised 29 January 2021, Accepted 30 January 2021, Available online 5 February 2021.

Abstract:

The increasing volume of waste streams require new biological technologies that can address pollution concerns while offering sustainable products. Purple phototrophic bacteria (PPB) are very versatile organisms that present a unique metabolism that allows them to adapt to a variety of environments, including the most complex waste streams. Their successful adaptation to such demanding conditions is partly the result of internal polymers accumulation which can be stored for electron/energy balance or as carbon and nutrients reserves for deprivation periods. Polyhydroxyalkanoates, glycogen, sulphur and polyphosphate are examples of polymers produced by PPB that can be economically explored due to their applications in the plastic, energy and fertilizers sectors. Their large-scale production implies the outdoor operation of PPB systems which brings new challenges, identified in this review. An overview of the current PPB polymer producing technologies and prospects for their future development is also provided.

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J. Fradinho, L.D. Allegue, M. Ventura, J.A. Melero, M.A.M. Reis, D. Puyol,
Up-scale challenges on biopolymer production from waste streams by Purple Phototrophic Bacteria mixed cultures: A critical review,
Bioresource Technology, Volume 327, 2021, 124820, ISSN 0960-8524.

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https://doi.org/10.1016/j.biortech.2021.124820

“Alkalinity, and Not the Oxidation State of the Organic Substrate, Is the Key Factor in Domestic Wastewater Treatment by Mixed Cultures of Purple Phototrophic Bacteria”

with interesting results on  optimization of domestic wastewater treatment using PPB (Purple Phototrophic Bacteria) in the Special Issue “Resource Recovery from Wastewater” of the Journal Ressources, Volume 9, Issue 7.

Published: July, 20th, 2020.

Abstract

Domestic wastewater treatment by purple phototrophic bacteria (PPB) is based on the assimilative uptake of organics and nutrients into the bacterial biomass. Thereby, it strongly depends on the carbon/nutrients ratio of the wastewater. The physiological COD/N/P ratio for PPB growth in domestic wastewater makes the addition of an external organic carbon source necessary in order to allow for an efficient process. However, PPB need a source of alkalinity (as CO2) to grow on reduced organics that serves as an electron acceptor since biohydrogen production (an alternative electron sink) is inhibited by ammonium. A preliminary experiment showed that high nutrients-loading wastewater was limited by CO2 imbalance, leading to poor removal efficiencies. Subsequently, the effect of the oxidation state of the organics added as external organic carbon sources to PPB reactors treating low nutrients-loading domestic wastewater has been analyzed. Three organics were used as additives to PPB development in four consecutive batches: acetate (more oxidized), ethanol and butyrate (more reduced). The PPB population was settled and the general performance under the three situations, in terms of organics, N and P assimilation, and growth kinetics was not significantly different irrespective of the external organic carbon source. The reactors were dominated by PPB, though reduced organics allowed for dominance of Rhodopseudomonas palustris, whereas oxidized organics caused co-dominance of R. palustris and Rhodobacter capsulatus. Thereby, alkalinity (as bicarbonate), and not the oxidation state of the organics, is the key parameter for the efficient treatment of domestic wastewater by PPB.

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Nairn, C.; Rodríguez, I.; Segura, Y.; Molina, R.; González-Benítez, N.; Molina, M.C.; Simarro, R.; Melero, J.A.; Martínez, F.; Puyol, D. Alkalinity, and Not the Oxidation State of the Organic Substrate, Is the Key Factor in Domestic Wastewater Treatment by Mixed Cultures of Purple Phototrophic Bacteria. Resources 2020, 9, 88.

Find the article under this link:

https://doi.org/10.3390/resources9070088.

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Resources Article “Alkalinity, and Not the Oxidation State of the Organic Substrate, Is the Key Factor in Domestic Wastewater Treatment by Mixed Cultures of Purple Phototrophic Bacteria”.

As the first official DEEP PURPLE publication, Luis D. Allegue, Daniel Puyol and Juan Antonio Melero Novel, from the Group of Chemical and Environmental Engineering, Universidad Rey Juan Carlos, published “Novel approach for the treatment of the organic fraction of municipal solid waste: Coupling thermal hydrolysis with anaerobic digestion and photo-fermentation” in ELSEVIER, “Science of the Total Environment”.

The publication is with open access under a Creative Commons license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Download and view the entire publication here: Sciencedirect-20200122

or follow this link.