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Projeto de investigação
Eco-efficient bioprocess for valorisation of saline resources towards the production of PHA biopolymers
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Donnan Dialysis for Recovering Ammonium from Fermentation Solutions Rich in Volatile Fatty Acids
Publication . Barros, Kayo Santana; Carvalheira, Mónica; Marreiros, Bruno Costa; Reis, Maria Ascensão M.; Crespo, João Goulão; Pérez-Herranz, Valentín; Velizarov, Svetlozar; DQ - Departamento de Química; LAQV@REQUIMTE; UCIBIO - Applied Molecular Biosciences Unit; MDPI AG
For the production of polyhydroxyalkanoates (PHA) using nitrogen-rich feedstocks (e.g., protein-rich resources), the typical strategy of restricting cell growth as a means to enhance overall PHA productivity by nitrogen limitation is not applicable. In this case, a possible alternative to remove the nitrogen excess (NH4+/NH3) is by applying membrane separation processes. In the present study, the use of Donnan dialysis to separate ammonium ions from volatile fatty acids present in the media for the production of PHA was evaluated. Synthetic and real feed solutions were used, applying NaCl and HCl receiver solutions separated by commercial cation-exchange membranes. For this specific purpose, Fumasep and Ralex membranes showed better performance than Ionsep. Sorption of ammonium ions occurred in the Ralex membrane, thus intensifying the ammonium extraction. The separation performances with NaCl and HCl as receiver solutions were similar, despite sorption occurring in the Ralex membrane more intensely in the presence of NaCl. Higher volumetric flow rates, NaCl receiver concentrations, and volume ratios of feed:receiver solutions enhanced the degree of ammonium recovery. The application of an external electric potential difference to the two-compartment system did not significantly enhance the rate of ammonium appearance in the receiver solution. The results obtained using a real ammonium-containing solution after fermentation of cheese whey showed that Donnan dialysis can be successfully applied for ammonium recovery from such solutions.
Pilot-scale valorisation of salmon peptone into polyhydroxyalkanoates by mixed microbial cultures under conditions of high ammonia concentration
Publication . Marreiros, Bruno C.; Carvalheira, Mónica; Henriques, Cláudia; Pequito, Daniela; Nguyen, Yen; Solstad, Runar G.; Eksteen, J. Johannes; Reis, Maria A. M.; UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; Elsevier BV
The aquaculture industry produces vast amounts of organic side streams that are often ensilaged for later use in low value applications. However, the potential of converting fish silage, particularly the proteinaceous fraction, into more economically valuable products such as biodegradable polyhydroxyalkanoates (PHA), has not been explored. This study investigates the valorisation of salmon peptone, the proteinaceous fraction obtained from salmon silage, into PHA by mixed microbial cultures (MMC) under conditions without nutrient limitation, where the high concentration of ammonia (up to 2.3 ± 0.2 gN/L) which the culture was subjected to has not been previously reported. Acidogenic fermentation of salmon peptone (SP) was attained in a continuous reactor, resulting in the production of a fermentate rich in acetate and butyrate (16.4 ± 1.6 gCODFP/L). The enriched MMC with PHA-accumulating organisms was selected in a sequential batch reactor (SBR) under nutrient-rich conditions (100 gCOD: 27.6 gN: 0.48 gP at OLR 7.1 gCODFP/(L.d)). The dominant microorganisms in the enriched culture were from the genus Brachymonas, which are described as capable of simultaneous cell growth and PHA accumulation, storing up to 53.0 ± 3.4% wt. of P(3HB-co-3HV) with a 3HV content of 34% wt. Despite the high ammonia concentration and constant nutrient availability, a good overall PHA yield (189 gPHA/kgSP) and global volumetric PHA productivity (3.10 ± 0.11 gPHA/(L.h)) were achieved. The results demonstrate the technological feasibility of producing PHA from salmon peptone under conditions that are typically considered unfavorable for PHA accumulation, which represents a significant novelty of this work.
Evaluation of fouling phenomena and cation-exchange membrane cleaning in Donnan dialysis for separation of ammonium from fermented solutions rich in volatile fatty acids
Publication . Barros, Kayo Santana; Marreiros, Bruno C.; Carvalheira, Mónica; Reis, Maria A. M.; Crespo, João Goulão; Pérez-Herranz, Valentín; Velizarov, Svetlozar; DQ - Departamento de Química; LAQV@REQUIMTE; UCIBIO - Applied Molecular Biosciences Unit; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Elsevier
Polyhydroxyalkanoates (PHA) are promising biobased and biodegradable alternatives to the petroleum-based plastics. For their production, controlling cell growth is crucial and can be achieved by limiting nutrients, such as ammonium. The use of Donnan dialysis (DD) has been considered for this purpose. However, the effects of long–term DD fermentative operations need to be evaluated since fouling and sorption phenomena can affect the process performance. In this study, DD operations were performed over 10 consecutive batches to separate ammonium from a real fermented stream derived from an acidogenic fermentation process using cation-exchange membranes with distinct properties (a homogenous Fumasep FKS–PET-130 and a heterogenous Ralex CMH-PES) and NaCl or HCl aqueous receiver solutions. A cleaning procedure with acidic and alkaline solutions was proposed for the Ralex. It was verified that sorption and fouling phenomena occurred on/inside both membranes using a NaCl solution as receiver. This occurred more intensely with the Ralex, thus reducing the ammonium percent extraction from 55% (first batch) to approximately 40% in the subsequent batches. On the other hand, Fumasep exhibited higher percent extractions, and its values remained constant at around 65% along the batches when only rinsed with distilled water. The proposed cleaning procedure for Ralex effectively regenerated this membrane and increased the subsequent ammonium percent extractions. However, the acidic and/or alkaline solutions formed cavities on/in the membrane. The use of a HCl solution as receiver led to a lower reduction in the percent extraction throughout the batches when compared to NaCl, but the acidic receiver solution also damaged the membrane. It is suggested the use of the Fumasep membrane for the application evaluated herein or that a milder cleaning procedure is developed and applied for the Ralex membrane.
Impact of saline osmotic stress on halotolerant polyhydroxyalkanoate (PHA)-accumulating mixed microbial cultures
Publication . Giovanella, Alice; Carvalheira, Mónica; Grana, Matteo; Reis, Maria A. M.; Marreiros, Bruno C.; UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; Elsevier BV
Bioconversion of saline organic side-streams into value-Added products, such as polyhydroxyalkanoates (PHAs), can reduce treatment costs and contribute to a circular economy. PHA production by Mixed Microbial Cultures (MMC) under saline conditions enables the use of salty side-streams and seawater (∼3.5-w/v NaCl) as process water, further enhancing the economic and environmental sustainability of the process, particularly for industries located at coastal sites. This study investigates a strategy to further improve the PHA production capacity of PHA-Accumulating MMC selected under near seawater salinity. Specifically, the selected culture was evaluated for its PHA production capacity under sudden osmotic imbalances by subjecting it to osmotic downshock (30-0-gNaCl/L) and upshock (30-60-gNaCl/L). The culture was enriched under double selective pressure (F/f regime and uncoupled C/N feeding) at 30 gNaCl/L, leading to the dominance of Neptunomonas phycophila (79.7-). During PHA accumulation, a maximum PHA content of 42.4-wt. was achieved, with a resulting P(3HB-co-3HV) copolymer containing 45-wt. 3HV. Osmotic downshock (<30 gNaCl/L) resulted in a 1.4-fold increase in PHA content (56.9 %) and storage yield compared to the control (30 gNaCl/L), while high osmotic upshock (60 gNaCl/L) had a negative effect. Additionally, varying food-To-microorganism (F/M) ratios and saline concentrations allowed the production of polymers with varying 3HB monomeric content (53-to 72 %), expanding the potential applications of these polymers.
Effect of pH on the selective electrodialytic recovery of acidogenic-derived volatile fatty acids
Publication . Barros, Kayo Santana; Marreiros, Bruno C.; Martí-Calatayud, Manuel César; Crespo, João Goulão; Pérez-Herranz, Valentín; Velizarov, Svetlozar; DQ - Departamento de Química; LAQV@REQUIMTE; UCIBIO - Applied Molecular Biosciences Unit; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Elsevier
Electrodialysis can be utilized to separate acidogenic-derived volatile fatty acids (VFA) used in the production of biobased and biodegradable polyhydroxyalkanoates (PHA). All VFAs are commonly recovered simultaneously in the receiver solution, although their selective recovery could benefit the fermentation process. The effect of membrane type, electric voltage and time on this selective recovery has been studied, but the impact of solution pH — an essential factor in organic acidś separation — remains still not sufficiently explored. Herein, the effect of the initial feed pH on the fractionation degree of four VFAs commonly present in fermented solutions — namely acetic, propionic, butyric, and valeric acid — was systematically evaluated. Three distinct anion-exchange membranes were tested: Ralex AMH-PES, Fumasep FAS-PET-130, and PC200D. It was found that pH significantly influenced VFA separation with the PC200D membrane, particularly enhancing the transfer of smaller organic anions, such as acetate and propionate, while the percent extraction (PE%) of larger anions, such as butyrate and valerate, remained practically unchanged as the pH increased. Thus, the higher the pH, the greater the fractionation degree achieved. For the electrodialysis operated with a feed solution at pH 7, ratios of (PEAc + PEProp)/(PEBut + PEVal) and PEAc/PEVal of 1.6 and 2.0, respectively, were obtained. This may be related to the presence of tertiary amines in the PC200D's fixed groups, which enhanced water dissociation occurrence. The transfer of VFAs through the Ralex and Fumasep membranes was less affected by pH as they contain only quaternary ammonium as their fixed charged groups.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/BTA-BTA/30902/2017