Two-phase Partitioning Bioreactor Research Articles

Effect of polymer molecular weight distribution on solute sequestration in two-phase partitioning bioreactors

Polymeric solids are effective absorbents in two-phase partitioning bioreactors (TPPBs) when they provide adequate absorptive capacity for the target solute, as well as the physical properties required by solid–liquid TPPB operations. This study demonstrates the influence of molecular weight distribution (MWD) on solute uptake, as measured by solute partition coefficient (PC), and mechanical strength, as measured by the polymer’s complex modulus (G∗). Experimental PC data for n-octanol absorption from aqueous solution by poly(dimethyl siloxane) (PDMS) demonstrate a decline in absorptive capacity with increasing number average molecular weight (Mn), in agreement with Flory–Huggins solution theory predictions. Importantly, MWD is shown to have no effect on solute uptake, with both unimodal and bimodal distributions generating the same PC at a given Mn. This is in contrast to G∗, whose MWD sensitivity is exploited to formulate bimodal mixtures of poly(isobutylene) (PIB) that provide high n-octanol PC values as well as satisfactory material strength. This bimodal MWD strategy to TPPB absorbent design is extended to miscible solutions of high MW PIB and cyclohexylbenzene, which are shown to generate superior n-octanol PC at a given G∗.

Xenobiotic removal from wastewater in a two-phase partitioning bioreactor: Process modelling and identification of operational strategies

This paper proposes a dynamic model simulating the performance of a fed batch system operated as solid–liquid two-phase partitioning bioreactor, with polymer beads as the sequestering phase, applied to the removal of xenobiotic compounds from concentrated aqueous streams, in which substrate inhibition is significant. The model takes into account substrate mass transfer into, and within, the solid particles. Outputs of the models are xenobiotic concentrations in the liquid and solid phases and the concentration profile within the solid polymer beads. Sensitivity analyses have been performed on the influent concentration and on the main operating parameters, which can be modified to control the process performance (i.e. polymer/feed ratio, reaction and loading times). With an inhibitory substrate, the selected duration of the reaction period exhibits a critical value which determines the transition from high to low efficiency of the bioreactor. Application examples are provided for a target compound, 4-nitrophenol, previously investigated in TPPBs with an immiscible organic solvent, while Hytrel 8206 has been considered as the polymer partitioning phase. The proposed model has been shown to be a powerful tool to predict suitable operating conditions for TPPB systems treating inhibitory substrates.

Produced water treatment using two-phase partitioning bioreactor

Produced waters (PW) are the largest waste associated to the production of oil and gas; they contain dissolved salts, oil (dissolved and scattered organic compounds), chemicals and salt intolerant additives to the oil well operations, suspended particles, sand and other compounds, making their treatment very tricky. In this paper, we propose the use of a two-phase partitioning bioreactor (TPPB) for the biological treatment of PWs. We model the application the TPPB on the stream after classical pre-treatment stages: the reactor functioning is based on the controlled release of substrate by means of a solvent. This study aims at developing a mathematical model for a TPPB adopting oleic alcohol (Adol 85 NF) as a solvent; we test its reliability by means of a sensitivity analysis, so to evaluate its efficiency for COD removal in a PW stream, aimed at water reuse.

Ex situ bioremediation of chlorophenol contaminated soil: comparison of slurry and solid‐phase bioreactors with the two‐step polymer extraction‐bioregeneration process

AbstractBACKGROUNDAn innovative approach for ex situ soil bioremediation, based on absorptive polymers extraction combined with biological regeneration of the polymer in a two‐phase partitioning bioreactor (TPPB), was tested to remediate soil contaminated by chlorophenols. The objective of the study was to evaluate the performance of the proposed technology in comparison with conventional technologies, such as slurry bioreactors and solid‐phase bioreactors.RESULTSA soil highly contaminated (∼4 g kg−1 for each compound) by a mixture of 4‐chlorophenol (4CP) and pentachlorophenol (PCP), was treated with different bioremediation systems. Removal efficiencies achieved with polymer extraction were >70% for a contact time of 24 h; the contaminated polymer was then regenerated in a TPPB (∼100 and 85% biodegradation efficiencies for 4CP and PCP, respectively). No degradation of PCP occurred in conventional bioreactors, while, for 4CP, 40 days were required for its biodegradation in the slurry bioreactor, and 80 days to reach 67% removal in the solid‐phase bioreactor.CONCLUSIONAdvantages of the two‐step polymer‐based soil treatment in comparison with conventional technologies have been demonstrated for chlorophenols contaminated soils: efficiencies in the range 70–80% for soil decontamination and almost complete mineralization of the two compounds were achieved with reaction times suitable for application (<20 days). © 2016 Society of Chemical Industry

SIFT-MS analysis of the removal of dimethyl sulphide, n-hexane and toluene from waste air by a two phase partitioning bioreactor

Dimethyl sulphide (DMS), n-hexane and toluene removal from a waste air was carried out by a two phase partitioning bioreactor (TPPR) containing a 25/75vol/vol silicone oil/water emulsion inoculated with activated sludge under continuous feeding conditions. The performance of the reactor was determined using two different measuring techniques, GC-FID and SIFT-MS in order to determine the feasibility of the SIFT-MS as analytical technique. The linearity between both measurement techniques indicated that SIFT-MS can be used as a suitable alternative to determine the bioreactor performance. When feeding the TPPR only with hexane, elimination capacities (EC) of 139, 164 and 242gm−3h−1 are reached for an inlet load (IL) of 350gm−3h−1 at respectively 30, 60 and 120s empty bed residence time (EBRT). If a mixture of DMS, hexane and toluene is fed to the bioreactor at an EBRT of 60s EC of respectively 45, 45 and 75gm−3h−1 are reached for the different compound at an IL of 100gm−3h−1. This indicates that a TPPR can be applied to treat a mixture of hydrophobic and hydrophilic compounds. Excessive growth of biomass in a TPPR can lead to deteriorated aeration and a decrease in performance. By using pulse injections, the net retention time of the compounds could be determined online, which is related to the aeration and air distribution within the reactor. A low net retention time indicates bad aeration and air distribution, resulting in a low reactor performance. Therefore the net retention time can be used as a parameter indicating when biomass needs to be purged or when the aqueous medium needs to be refreshed.

Synthesis and toxicity evaluation of hydrophobic ionic liquids for volatile organic compounds biodegradation in a two-phase partitioning bioreactor

Synthesis of several hydrophobic ionic liquids (ILs), which might be selected as good candidates for degradation of hydrophobic volatile organic compounds in a two-phase partitioning bioreactor (TPPB), were carried out. Several bioassays were also realized, such as toxicity evaluation on activated sludge and zebrafish, cytotoxicity, fluoride release in aqueous phase and biodegradability in order to verify their possible effects in case of discharge in the aquatic environment and/or human contact during industrial manipulation. The synthesized compounds consist of alkylimidazoliums, functionalized imidazoliums, isoqinoliniums, triazoliums, sulfoniums, pyrrolidiniums and morpholiniums and various counter-ions such as: PF6−, NTf2− and NfO−. Toxicity evaluation on activated sludge of each compound (5% v/v of IL) was assessed by using a glucose uptake inhibition test. Toxicity against zebrafish and cytotoxicity were evaluated by the ImPACCell platform of Rennes (France). Fluoride release in water was estimated by regular measurements using ion chromatography equipment. IL biodegradability was determined by measuring BOD28 of aqueous samples (compound concentration,1mM). All ILs tested were not biodegradable; while some of them were toxic toward activated sludge. Isoquinolinium ILs were toxic to human cancerous cell lines. Nevertheless no toxicity was found against zebrafish Danio rerio. Only one IL released fluoride after long-time agitation.

Characterization of pH dependence in organic acid absorption with non-reactive and reactive polymers for application in two-phase partitioning bioreactors

Strategies for extracting organic acids from aqueous solutions using polymeric absorbents are demonstrated and discussed in the context of two-phase partitioning bioreactor (TPPB) design. Experimental data and material balances for the uptake of butyric acid and benzoic acid by a poly(ether-block-amide) copolymer (Pebax 2533) establish the inherent limitations of unreactive absorbents for organic acid bioprocesses that operate at near-neutral pH. Improvements to TPPB performance are achieved by lowering pH temporarily with CO2 to enhance acid absorption, and removing the solute-rich polymer before restoring pH to fermentative values by releasing the CO2 pressure. Butyric acid removal by Pebax 2533 improved from 3% to 40% upon acidifying a pH 6 solution with 60bar of CO2, while benzoic acid absorption increased from 1% to 80% using this pressure manipulation technique. A reactive extraction approach involving a newly-synthesized amine functionalized hydrogel is also described wherein acid/base reaction equilibrium governs the extent of solute uptake. Copolymerization of 2-(dimethylamino)ethyl acrylate (DMAEA) and trimethylolpropane triacrylate (TMPTA) yielded a thermoset material with sufficient basicity to remove 80% of both butyric and benzoic acid from aqueous solution using just 1wt% polymer relative to the aqueous phase mass.

Two phase partitioning bioreactor applied to produced water treatment

Produced waters are the largest waste associated with the production of oil and gas; they contain dissolved salts, oil (dissolved and scattered organic compounds), chemicals and additives involved in the oil well operations, suspended particles, sand and other compounds, making their treatment very complex. In this paper, we propose the use of a TPPB (two phase partitioning bioreactor) for the biological treatment of produced waters. We model the application of the TPPB on the stream after classical pre-treatment stages: the reactor behaviour is based on the controlled release of substrate by means of an organic solvent. This study aims at developing a mathematical model for a TPPB adopting oleic alcohol (Adol 85 NF) as a solvent: we test model reliability by means of a sensitivity analysis in order to evaluate the reactor efficiency for chemical oxygen demand (COD) removal in a produced water stream, aimed at water reuse.

Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection.

Absorption and biodegradation of toluene: Optimization of its initial concentration and the biodegradable non-aqueous phase liquid volume fraction

Di (2-EthylHexyl) Phthalate (DEHP) was selected as a biodegradable organic solvent to be implemented in a two-phase partitioning bioreactor (TPPB) dedicated to remove a model hydrophobic volatile organic compound (VOC), toluene. In a first step, the absorption capacity of toluene in the selected organic solvent was examined according to the partition coefficients H. In a second step, toluene biodegradation in DEHP by non-acclimated activated sludge was carried out for different volume fractions of DEHP in water and five different toluene concentrations (4.3, 43, 106, 212 and 430 mg l−1). Toluene showed high affinity for DEHP with H = 0.99 Pa m3 mole−1. Both toluene and DEHP were completely consumed for 4.3 mg l−1 (initial toluene concentration) and a volume ratio of 0.1% DEHP in water. For an initial toluene concentration of 106 mg l−1 and a volume ratio of 0.1%, total toluene consumption and 87% DEHP degradation yield were obtained after seven days of incubation.

Biocompatibility of low molecular weight polymers for two-phase partitioning bioreactors.

Two phase partitioning bioreactors (TPPBs) improve the efficiency of fermentative processes by limiting the exposure of microorganisms to toxic solutes by sequestering them into a non-aqueous phase (NAP). A potential limitation of this technology, when using immiscible organic solvents as the NAP, is the cytoxicity that these materials may exert on the microbes. An improved TPPB configuration is one in which polymeric NAPs are used to replace organic solvents in order to take advantage of their low cost, improved handling qualities, and biocompatibility. A recent study has shown that low molecular weight polymers may confer improved solute uptake relative to high molecular weight polymers (i.e., have higher partition coefficients), but it is unknown whether sufficiently low molecular weight polymers may inhibit cell growth. This study has investigated the biocompatibility of a range of low molecular weight polymers, and compared trends in biocompatibility to the well-established "critical log P" concept. This was achieved by determining the biocompatibility of polypropylene glycol polymers over a molecular weight (MW) range of 425-4,000 to Saccharomyces cerevisiae and Pseudomonas putida, two organisms which have been previously used in TPPB systems. The lower MW polymers were shown to have lower average log P values, and showed more cytotoxicity than polymers of the same structure but with higher molecular weight. Since polymers are generally polydisperse (i.e., polymer samples contain a distribution of MWs), removal of the lower MW fractions via water washing was found to result in improved polymer biocompatibility. These results suggest that the critical log P concept remains useful for describing the toxicity of polymeric substances of different MWs, although it is complicated by the presence of the low MW fractions in the polymers arising from polydispersity.

Regeneration strategies of polymers employed in ex-situ remediation of contaminated soil: Bioregeneration versus solvent extraction

In this study we evaluated the feasibility of two regeneration strategies of contaminated polymers employed for ex-situ soil remediation in a two-step process. Soil decontamination is achieved by sorption of the pollutants on the polymer beads, which are regenerated in a subsequent step. Tested soil was contaminated with a mixture of 4-chlorophenol and pentachlorophenol, and a commercial polymer, Hytrel, has been employed for extraction. Removal efficiencies of the polymer-soil extraction are in the range of 51–97% for a contact time≤24 h. Two polymer regeneration strategies, solvent extraction and biological regeneration (realized in a two-phase partitioning bioreactor), were tested and compared. Performance was assessed in terms of removal rates and efficiencies and an economic analysis based on the operating costs has been performed. Results demonstrated the feasibility of both regeneration strategies, but the bioregeneration was advantageous in that provided the biodegradation of the contaminants desorbed from the polymer. Practically complete removal for 4-chlorophenol and up to 85% biodegradation efficiency for pentachlorophenol were achieved. Instead, in the solvent extraction, a relevant production (184–831 L kgpol−1) of a highly polluted stream to be treated or disposed of is observed. The cost analysis of the two strategies showed that the bioregeneration is much more convenient with operating costs of ∼12 €/kgpol i.e. more than one order of magnitude lower in comparison to ∼233 €/kgpol of the solvent extraction.

Mass transfer considerations in solid-liquid two-phase partitioning bioreactors: a polymer selection guide

BACKGROUND Selection of polymers for two-phase partitioning bioreactors (TPPBs) has been focused primarily on predicting a polymer's affinity for the target molecule. Although the extent to which a polymer absorbs a solute is important, the rate of uptake/release must be sufficiently rapid such that a TPPB is not mass transfer limited. This work focused on developing a guide to identify combinations of polymer diffusivities and diffusional path lengths that will ensure a TPPB is not limited by substrate delivery. RESULTS TPPB systems limited by substrate delivery yielded linear growth, while biologically limited systems exhibited exponential growth. Release rates of phenol from various polymer phases increased as polymer diffusivity increased, or as diffusional path length (polymer bead size) decreased. A polymer selection guide was developed identifying combinations of polymer diffusivity and bead size that will ensure a TPPB is not mass transfer limited, for a desired maximum substrate consumption rate. CONCLUSION In selecting polymers for TPPB applications, solute affinity (extent of uptake) has been relatively well characterized using first principles methods, and the present work has now ‘completed the picture’ by providing a description of polymer transport properties (diffusivity and diffusional path length) to be able to generate a guide for selecting polymers. © 2015 Society of Chemical Industry

A novel mathematical approach for the understanding and optimization of two-phase partitioning bioreactors devoted to air pollution control

Two-phase partitioning bioreactors (TPPBs) support the removal of volatile organic compounds (VOCs) from contaminated gaseous emissions at unprecedented rates and concentrations. TPPBs are biological multiphase systems provided with a non-aqueous phase (NAP) with high affinity for the target VOC. Although modeling of TPPBs is a research field that has rapidly evolved, recent experimental findings such as the direct VOC uptake from liquid NAPs and the quantification of simultaneous partial mass transfer coefficients have not been incorporated yet in a comprehensive mathematical description. In this work, a mathematical description of TPPBs, including continuous aqueous phase renewal and potential VOC uptake directly from the NAP, was developed. Model simulations indicated that TPPB performance can be enhanced by improving the partial mass transfer coefficient between the gas and the NAP (by increasing the contact between the gas and the NAP). The model also showed that microorganisms with half-saturation constants <5gm−3 and ability to take up VOC directly from the NAP can boost significantly TPPB performance. The present modeling platform was tested against experimental data from literature for methane, hexane and dichloromethane and no parameter fitting was carried out.

Coupling extraction and enzyme catalysis for the removal of anthracene present in polluted soils

In this study, a novel system for removing anthracene from polluted soils using biodegradable vegetable oil was investigated. The process consisted of the extraction of anthracene from the soil (1004mg/kg) by pomace olive oil followed by its degradation in a surfactant-assisted two phase partitioning bioreactor (TPPB), operated with a laccase-mediator system. The main outcomes of this study showed high extraction efficiency for both fresh and regenerated pomace olive oil (higher than 84%) and almost complete removal of anthracene in the TPPB after 48h. Finally, the feasibility of reusing both the aqueous and organic phases of the TPPB in successive batches of anthracene degradation in the bioreactor was also demonstrated.

Mandelic acid chiral separation utilizing a two-phase partitioning bioreactor built by polysulfone microspheres and immobilized enzymes.

A novel two-phase partitioning bioreactor (TPPB) modified by polysulfone (PSF) microspheres and immobilized enzyme (novozym-435) was formed, and the resulting TPPB was applied into mandelic acid chiral separation. The PSF microspheres containing n-hexanol (named PSF/hexanol microspheres) was prepared by using the phase inversion method, which was used as the organic phase. Meanwhile, the immobilized enzyme novozym-435 was used as a biocatalyst. The water phase was composed of the phosphate buffer solution(PBS). (R, S)-Methyl mandelate was selected as the substrate to study enzymatic properties. Different reaction factors have been researched, such as pH, reaction time, temperature and the quantity of biocatalyst and PSF/hexanol microspheres added in. Finally, (S)-mandelic acid was obtained with an 80% optical purity after 24h in the two-phase partitioning bioreactor. The enantiomeric excess (eep) values were very low in the water phase, in which the highest eep value was only 46%. The eep of the two-phase partitioning bioreactor had been enhanced more obviously than that catalyzed in the water phase.

Assessment of methane biodegradation kinetics in two-phase partitioning bioreactors by pulse respirometry

Biological methane biodegradation is a promising treatment alternative when the methane produced in waste management facilities cannot be used for energy generation. Two-phase partitioning bioreactors (TPPBs), provided with a non-aqueous phase (NAP) with high affinity for the target pollutant, are particularly suitable for the treatment of poorly water-soluble compounds such as methane. Nevertheless, little is known about the influence of the presence of the NAP on the resulting biodegradation kinetics in TPPBs. In this study, an experimental framework based on the in situ pulse respirometry technique was developed to assess the impact of NAP addition on the methane biodegradation kinetics using Methylosinus sporium as a model methane-degrading microorganism. A comprehensive mass transfer characterization was performed in order to avoid mass transfer limiting scenarios and ensure a correct kinetic parameter characterization. The presence of the NAP mediated significant changes in the apparent kinetic parameters of M. sporium during methane biodegradation, with variations of 60, 120, and 150% in the maximum oxygen uptake rate, half-saturation constant and maximum specific growth rate, respectively, compared with the intrinsic kinetic parameters retrieved from a control without NAP. These significant changes in the kinetic parameters mediated by the NAP must be considered for the design, operation and modeling of TPPBs devoted to air pollution control.

The use of high pressure CO2‐facilitated pH swings to enhance in situ product recovery of butyric acid in a two‐phase partitioning bioreactor

Through the use of high partial pressures of CO2 (pCO2 ) to facilitate temporary pH reductions in two-phase partitioning bioreactors (TPPBs), improved pH dependent partitioning of butyric acid was observed which achieved in situ product recovery (ISPR), alleviating end-product inhibition (EPI) during the production of butyric acid by Clostridium tyrobutyricum (ATCC 25755). Through high pressure pCO2 studies, media buffering effects were shown to be substantially overcome at 60 bar pCO2 , resulting in effective extraction of the organic acid by the absorptive polymer Pebax® 2533, yielding a distribution coefficient (D) of 2.4 ± 0.1 after 1 h of contact at this pressure. Importantly, it was also found that C. tyrobutyricum cultures were able to withstand 60 bar pCO2 for 1 h with no decrease in growth ability when returned to atmospheric pressure in batch reactors after several extraction cycles. A fed-batch reactor with cyclic high pCO2 polymer extraction recovered 92 g of butyric acid to produce a total of 213 g compared to 121 g generated in a control reactor. This recovery reduced EPI in the TPPB, resulting in both higher productivity (0.65 vs. 0.33 g L(-1) h(-1) ) and yield (0.54 vs. 0.40). Fortuitously, it was also found that repeated high pCO2 -facilitated polymer extractions of butyric acid during batch growth of C. tyrobutyricum lessened the need for pH control, and reduced base requirements by approximately 50%. Thus, high pCO2 -mediated absorptive polymer extraction presents a novel method for improving process performance in butyric acid fermentation, and this technique could be applied to the bioproduction of other organic acids as well.

Modeling of crude oil biodegradation using two phase partitioning bioreactor

In this work, crude oil biodegradation has been optimized in a solid-liquid two phase partitioning bioreactor (TPPB) by applying a response surface methodology based d-optimal design. Three key factors including phase ratio, substrate concentration in solid organic phase, and sodium chloride concentration in aqueous phase were taken as independent variables, while the efficiency of the biodegradation of absorbed crude oil on polymer beads was considered to be the dependent variable. Commercial thermoplastic polyurethane (Desmopan®) was used as the solid phase in the TPPB. The designed experiments were carried out batch wise using a mixed acclimatized bacterial consortium. Optimum combinations of key factors with a statistically significant cubic model were used to maximize biodegradation in the TPPB. The validity of the model was successfully verified by the good agreement between the model-predicted and experimental results. When applying the optimum parameters, gas chromatography-mass spectrometry showed a significant reduction in n-alkanes and low molecular weight polycyclic aromatic hydrocarbons. This consequently highlights the practical applicability of TPPB in crude oil biodegradation.

Block copolymers as sequestering phases in two‐phase biotransformations: effect of constituent homopolymer properties on solute affinity

AbstractBACKGROUNDBlock copolymers can be effective extractants in solid–liquid two‐phase partitioning bioreactors (TPPBs) when selected on the basis of their partition coefficient toward target solutes, and their thermo‐mechanical properties. A series of Pebax® block copolymers, containing varying proportions of soft poly(tetramethylene oxide) and hard poly(amide‐12), was evaluated to determine the effect of hard segment proportion on solute affinity toward two biotransformation target molecules, carveol and carvone. Subsequently, representative homopolymers comprising the copolymers' soft segment were examined individually for the effects of molecular weight, crystallinity, and polymer end group polarity on affinity.RESULTSPartition coefficients decreased with greater proportions of copolymer hard segments and homopolymer crystallinity, both of which act as non‐absorptive domains, but which impart mechanical strength to the polymer. Partition coefficients increased with decreasing homopolymer molecular weight, which was ascribed to increased entropy of mixing. Hydroxyl vs. ether end group functionality had a variable effect on the partitioning of polar and non‐polar solutes, providing a basis for the rational design of selective oligomeric absorbents.CONCLUSIONBlock copolymers can provide an attractive, low‐cost option for polymeric sequestering phases in TPPBs, but commercial grades of these materials are not optimized for these applications. TPPB performance can be improved by selecting/fabricating polymers that minimize the molecular weight of the soft component, the proportion of hard segment, and by considering the effects of end group composition. © 2014 Society of Chemical Industry