1,720,980 research outputs found
Waste-derived tuff for CO2 Capture: Enhanced CO2 adsorption performances by Cation-Exchange tailoring
No full textMitigating greenhouse gas emissions through CO2 capture from industrial flue gases is imperative for addressing climate change. This article delves into the potential of natural tuff, derived from construction and demolition (C&D) waste, as an affordable and sustainable CO2 adsorbent for post-combustion capture. By tailoring the tuff structure and chemical composition through cation-exchange, the crucial role of cation type in enhancing its textural properties, particularly its microporosity and specific surface area, has been highlighted. Notably, Li- and Na-exchanges greatly enhance these properties, indicating a heightened potential for CO2 capture. The work further explores the dynamic CO2 adsorption of both untreated and modified tuff in a fixed-bed reactor under low CO2 partial pressures (< 0.2 atm), particularly examining the effects of extra-framework cation nature (Na+, Li+) and composition, and the influence of NH4+ pre-treatment. Results show that Na- and Li-exchanged tuff exhibit enhanced CO2 uptake (up to 1 mmol g−1) compared to untreated tuff (0.54 mmol g−1), with Li-exchange resulting in the highest capacity due to both superior textural properties and stronger ion-quadrupole interactions with CO2 molecules. The multi-cyclic stability of the synthesized samples has been also assessed; regardless of the specific cation-exchange type, all the samples provide stable performances over 10 consecutive adsorption/desorption cycles
Immobilization of Actinobacillus succinigenes in Alginate Beads for Succinic Acid Production
No full textNowadays the succinic acid (SA) - a C-4 dicarboxylic acid - is considered as one of the most promising platform chemicals produced from renewable resources via fermentation. Enhancement of the SA fermentation efficiency and productivity may take advantages from immobilized cultures.. This work reports the immobilization of Actinobacillus succinogenes cells in calcium alginate beads. Glucose was used as carbon source for the fermentation. A parallel fermentation test with free cells was carried out to assess the advantages of the immobilization technology. The immobilization in alginate beads was proved to be an effective technique for SA production by A. succinogenes. The fermentation performances of the immobilized cells were higher than those of the free cells. In particular, at initial glucose concentrations of 40 g/L the maximum productivity in immobilized cells fermentation (0.77 g/Lh) is more than twice that measured for free cells (0.32 g/Lh
Continuous succinic acid production by immobilized cells of Actinobacillus succinogenes in a fluidized bed reactor: Entrapment in alginate beads
No full textThe production of succinic acid (SA) was investigated by using immobilized cultures of Actinobacillus succinogenes in alginate beads. Immobilized cell cultures operated in batch mode were tested by varying the initial glucose concentration between 20 and 80 g/L and the bead concentration (mass of beads per liter of fermentation broth) between 50 and 250 g/L. Free cells fermentation tests were also carried out to compare the performances of free cells vs. immobilized cells. The best results were obtained with immobilized cells at initial glucose concentration of 60 g/L and 250 g/L of beads: the final SA concentration was 69 ± 0.2 g/L and the SA yield was 1.15 ± 0.02 g/g. Repeated batch fermentation tests were performed to assess the mechanical stability of the alginate beads. The continuous fermentation process was investigated in a three-phase fluidized bed reactor (FBR) using cell entrapped in alginate beads (the solid phase). The process performances were studied and described as acid production (succinic acid included) and sugar conversion. The performances of the FBR were particularly attractive because it was possible to combine high SA productivity (35.6 g/Lh) with high SA concentration (31 g/L) and substrate conversion (76.4 %)
Bioreactors for succinic acid production processes
No full textSuccinic acid (SA) has been recognized as one of the most important bio-based building block chemicals due to its numerous potential applications. Fermentation SA production from renewable carbohydrate feedstocks can have the economic and sustainability potential to replace petroleum-based production in the future, not only for existing markets, but also for new larger volume markets. Design and operation of bio-reactors play a key role. During the last 20 years, many different fermentation strategies for SA production have been described in literature, including utilization of immobilized biocatalysts, integrated fermentation and separation systems and batch, fed-batch, and continuous operation modes. This review is an overview of different fermentation process design developed over the past decade and provides a perspective on remaining challenges for an economically feasible succinate production processes. The analysis stresses the idea of improving the efficiency of the fermentation stage by improving bioreactor design and by increasing bioreactor performance.</p
A novel integrated fermentation/recovery system for butanol production by <i>Clostridium acetobutylicum</i>
No full textIntensive butanol production was carried out by immobilized cells of Clostridium acetobutylicum in a novel continuous fermentation system. The fermentation system consisted of four packed bed biofilm reactors (PBBR) connected in series. The novelty of the proposed system is: i) the use of a novel stagewise simulated moving bed (SMB) design/operational mode; ii) the integration of the reaction and the product recovery sections. The SMB operational mode was accomplished by equipping the PBBR with manifolds and time-actuated switching valves. PBBR integration with the product recovery section was also tested. An adsorption column was operated between the 3rd and 4th reactor of the series.The tuning of the PBBR system overall dilution rate (DOV) allowed to maximize: i) sugar conversion (DOV <0.150 h−1); ii) butanol concentration (0.650 h−1<DOV<0.900 h-1); iii) butanol productivity (13.0 g/Lh at DOV=0.900 h-1).The PBBR system was upgraded by integrating it with an in-line adsorption column and it guaranteed a twofold increase in butanol productivity (up to 22 g/Lh) and an average butanol concentration close to 24.0 g/L
RETRACTED: Continuous H-B-E fermentation by Clostridium carboxidivorans: CO vs syngas
No full textLeveraging renewable carbon-based resources for energy and chemical production is a promising approach to decrease reliance on fossil fuels. This entails a thermo/biotechnological procedure wherein bacteria, notably Clostridia, ferment syngas, converting CO or CO2 + H2 into Hexanol, Butanol and Ethanol (H-B-E fermentation). This work reports of Clostridium carboxidivorans performance in a stirred tank reactor continuously operated with respect to the gas and the cell/liquid phases. The primary objective was to assess acid and solvent production at pH 5.6 by feeding pure CO or synthetic syngas under gas flow differential conditions. Fermentation tests were conducted at four different dilution rates (DL) of the fresh medium in the range 0.034-0.25 h-1. The fermentation pathways of C. carboxidivorans were found to be nearly identical for both CO and syngas, with consistent growth and metabolite production at pH 5.6 within a range of dilution rates. Wash-out conditions were observed at a DL of 0.25 h-1 regardless of the carbon source. Ethanol was the predominant solvent produced, but a shift towards butanol production was observed with CO as the substrate and towards hexanol production with synthetic syngas. In particular, the maximum cell concentration (0.5 gDM/L) was obtained with pure CO at DL 0.05 h-1; the highest solvent productivity (60 mg/L*h of total solvent) was obtained at DL 0.17 h-1 by using synthetic syngas as C-source. The findings highlight the importance of substrate composition and operating conditions in syngas fermentation processes. These insights contribute to the optimization of syngas fermentation processes for biofuel and chemical production
Optimization of CO fermentation by Clostridium carboxidivorans in batch reactors: Effects of the medium composition
Full text linkObjectives: The objective of this study was to investigate the effects of medium composition on CO fermentation by Clostridium carboxidivorans. The focus was to reduce the medium cost preserving acceptable levels of solvent production. Methods: Yeast extract (YE) concentration was set in the range of 0-3 g/L. Different reducing agents were investigated, including cysteine-HCl 0.6 g/L, pure cysteine 0.6 g/L, sodium sulphide (Na2S) 0.6 g/L, cysteine-sodium sulphide 0.6 g/L and cysteine-sodium sulphide 0.72 g/L. The concentration of the metal solution was decreased down to 25 % of the standard value. Fermentation tests were also carried out with and without tungsten or selenium. Results: The results demonstrated that under optimized conditions, namely yeast extract (YE) concentration set at 1 g/L, pure cysteine as the reducing agent and trace metal concentration reduced to 75 % of the standard value, reasonable solvent production was achieved in less than 150 h. Under these operating conditions, the production levels were found to be 1.39 g/L of ethanol and 0.27 g/L of butanol. Furthermore, the study revealed that selenium was not necessary for C. carboxidivorans fermentation, whereas the presence of tungsten played a crucial role in both cell growth and solvent production. Conclusions: The optimization of the medium composition in CO fermentation by Clostridium carboxidivorans is crucial for cost-effective solvent production. Tuning the yeast extract (YE) concentration, using pure cysteine as the reducing agent and reducing trace metal concentration contribute to reasonable solvent production within a relatively short fermentation period. Tungsten is essential for cell growth and solvent production, while selenium is not required
Bio-butanol separation by adsorption on various materials: Assessment of isotherms and effects of other ABE-fermentation compounds
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