Syngas fermentation to biofuel: Evaluation of carbon monoxide mass transfer and analytical modeling using a composite hollow fiber (CHF) membrane bioreactor
Department of Molecular Biosciences and Bioengineering (MBBE), University of Hawai'i at Mānoa, Agricultural Science Building 218, 1955 East-West Road, Honolulu, HI 96822, United States.Bioresource Technology (Impact Factor: 4.49). 03/2012; 122:130-6. DOI: 10.1016/j.biortech.2012.03.053
In this study, the volumetric mass transfer coefficients (Ka) for CO were examined in a composite hollow fiber (CHF) membrane bioreactor. The mass transfer experiments were conducted at various inlet gas pressures (from 5 to 30psig (34.5-206.8kPa(g))) and recirculation flow rates (300, 600, 900, 1200 and 1500mL/min) through CHF module. The highest Ka value of 946.61/h was observed at a recirculation rate of 1500mL/min and at an inlet gas pressure of 30psig(206.8kPa(g)). The findings of this study confirm that the use of CHF membranes is effective and improves the efficiency CO mass transfer into the aqueous phase.
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- "Additionally, the high requirement for energy-efficient mass transfer has led to the development of innovative bioreactor systems that incorporate microbubble generation (Bredwell and Worden, 1998; Bredwell et al., 1999) or immobilized hollow fiber membranes (Basu et al., 2008). Recent studies reported that hollow fiber membrane (HFM) bioreactors were effective in improving mass transfer of CO, in which the highest k L a for CO (950 to 1100 h − 1 ) could be achieved, making them attractive in syngas fermentation (Munasinghe and Khanal, 2012; Orgill et al., 2013; Shen et al., 2014). Although there are many parameters to be considered in designing reactor systems in syngas fermentation, HFM bioreactor could provide significant advantages over conventional reactor designs in terms of mass transfer of CO, and therefore HFM bioreactor is considered as one of the most promising reactor configurations. "
ABSTRACT: Among four basic mechanisms for biological hydrogen (H2) production, dark fermentation has been considered to show the highest hydrogen evolution rate (HER). H2 production from one-carbon (C1) compounds such as formate and carbon monoxide (CO) is promising because formate is an efficient H2 carrier, and the utilization of CO-containing syngas or industrial waste gas may render the industrial biohydrogen production process cost-effective. A variety of microbes with the formate hydrogen lyase (FHL) system have been identified from phylogenetically diverse groups of archaea and bacteria, and numerous efforts have been undertaken to improve the HER for formate through strain optimization and bioprocess development. CO-dependent H2 production has been investigated to enhance the H2 productivity of various carboxydotrophs via an increase in CO gas-liquid mass transfer rates and the construction of genetically modified strains. Hydrogenogenic CO-conversion has been applied to syngas and by-product gas of the steel-mill process, and this low-cost feedstock has shown to be promising in the production of biomass and H2. Here, we focus on recent advances in the isolation of novel phylogenetic groups utilizing formate or CO, the remarkable genetic engineering that enhances H2 productivity, and the practical implementation of H2 production from C1 substrates.Biotechnology Advances 11/2014; 33(1):165–177. DOI:10.1016/j.biotechadv.2014.11.004 · 9.02 Impact Factor
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- "We are currently studying improved reactor designs to reduce mass transfer limitations. For example, using hollow fiber membranes as diffusers has recently been reported to improve the mass transfer of CO in water (Lee et al., 2012; Munasinghe and Khanal, 2012). Two distinct rates of growth were observed in the bioreactor. "
ABSTRACT: Clostridium carboxidivorans P7 is one of three microbial catalysts capable of fermenting synthesis gas (mainly CO, CO(2) , and H(2) ) to produce the liquid biofuels ethanol and butanol. Gasification of feedstocks to produce synthesis gas (syngas), followed by microbial conversion to solvents, greatly expands the diversity of suitable feedstocks that can be used for biofuel production beyond commonly used food and energy crops to include agricultural, industrial, and municipal waste streams. C. carboxidivorans P7 uses a variation of the classic Wood-Ljungdahl pathway, identified through genome sequence-enabled approaches but only limited direct metabolic analyses. As a result, little is known about gene expression and enzyme activities during solvent production. In this study, we measured cell growth, gene expression, enzyme activity, and product formation in autotrophic batch cultures continuously fed a synthetic syngas mixture. These cultures exhibited an initial phase of growth, followed by acidogenesis that resulted in a reduction in pH. After cessation of growth, solventogenesis occurred, pH increased and maximum concentrations of acetate (41 mM), butyrate (1.4 mM), ethanol (61 mM), and butanol (7.1 mM) were achieved. Enzyme activities were highest during the growth phase, but expression of carbon monoxide dehydrogenase (CODH), Fe-only hydrogenases and two tandem bi-functional acetaldehyde/alcohol dehydrogenases were highest during specific stages of solventogenesis. Several amino acid substitutions between the tandem acetaldehyde/alcohol dehydrogenases and the differential expression of their genes suggest that they may have different roles during solvent formation. The data presented here provide a link between the expression of key enzymes, their measured activities and solvent production by C. carboxidivorans P7. This research also identifies potential targets for metabolic engineering efforts designed to produce higher amounts of ethanol or butanol from syngas. Biotechnol. Bioeng. 2012; 109: 2720-2728. © 2012 Wiley Periodicals, Inc.Biotechnology and Bioengineering 11/2012; 109(11):2720-8. DOI:10.1002/bit.24549 · 4.13 Impact Factor
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ABSTRACT: Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H(2) to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L)) of three reactor types; the TBR with 3mm and 6mm beads, five different modules of HFRs, and the STR. The analysis was performed using O(2) as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest K(tot)A/V(L) (1062h(-1)), followed by the TBR with 6mm beads (421h(-1)), and then the STR (114h(-1)). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed.Bioresource Technology 02/2013; 133C:340-346. DOI:10.1016/j.biortech.2013.01.124 · 4.49 Impact Factor
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