Treatment of substituted phenol mixtures in single phase and two-phase solid–liquid partitioning bioreactors (original) (raw)
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Solid-Liquid Partitioning Bioreactors Applied to the Removal of Mixtures of Phenolic Compounds
In this paper we report the results of an investigation on the performance of conventional and two phase partitioning bioreactors (TPPBs) operating in sequencing batch mode applied to the biodegradation of a binary mixture of 2 substituted phenols, 2,4-dimethylphenol and 4-nitrophenol. The TPPB was operated with the DuPont polymer Hytrel 8206 as the partitioning phase, which was demonstrated to be effective in the uptake and release of a variety of phenolic compounds. Partition tests were performed on both compounds, and partition coefficients of 201 and 143 were obtained in distilled water for 2,4-dimethylphenol and 4-nitrophenol, respectively. Parallel kinetic tests were carried out in conventional and TPPB bioreactors under the same operating conditions. The TPPB results showed a reduction in the aqueous phase concentration for both substrates to sub-inhibitory levels in all the tests, and the effect was more evident for 2,4 dimethylphenol as expected by the partition coefficient...
Biotechnology Progress, 2004
Two-Phase Partitioning Bioreactors (TPPBs) have traditionally been used to partition toxic concentrations of xenobiotics from a cell-containing aqueous phase by means of an immiscible organic solvent and to deliver these substrates back to the cells on the basis of metabolic demand and the maintenance of thermodynamic equilibrium between the phases. A limitation of TPPBs, which use organic liquid solvents, is the possibility that the solvent can be bioavailable, and this has therefore limited organic liquid TPPBs to the use of pure strains of microbes. Solid polymer beads have recently been introduced as a replacement for liquid organic solvents, offering similar absorption properties but with the capability to be used with mixed microbial populations. The present work was aimed at identifying a polymer with a greater capacity for and more rapid uptake and release of phenol for use as the second phase in a mixed culture TPPB. Polarity and hydrogen bonding capabilities between polymer and phenol were considered in the screening and selection process of candidate polymers. Hytrel (a copolymer of poly(butylene terephthalate) and butylene ether glycol terephthalate) polymer beads, offered improved capacity (19 mg phenol/g polymer at a fixed initial phenol concentration of 2000 mg/L) and a greater diffusivity (1.54 × 10-7 cm 2 /s) when compared to the capacity and diffusivity of previously used EVA (ethylene vinyl acetate) beads (12.4 mg phenol/g polymer and 3.73 × 10-9 cm 2 /s, respectively). Hytrel polymer beads were then used in a TPPB for the investigation of various substrate feeding strategies (fed-batch, bead replacement, and concentrated spikes of phenol), with rapid and complete phenol degradation shown in all cases.
Biodegradation of a phenolic mixture in a solid–liquid two-phase partitioning bioreactor
Applied Microbiology and Biotechnology, 2006
A solid-liquid two-phase partitioning bioreactor (TPPB) in which the non-aqueous phase consisted of polymer (HYTREL) beads was used to degrade a model mixture of phenols [phenol, o-cresol, and 4-chlorophenol (4CP)] by a microbial consortium. In one set of experiments, high concentrations (850 mg l −1 of each of the three substrates) were reduced to sub-inhibitory levels within 45 min by the addition of the polymer beads, followed by inoculation and rapid (8 h) consumption of the total phenolics loading. In a second set of experiments, the beneficial effect of using polymer beads to launch a fermentation inhibited by high substrate concentrations was demonstrated by adding 1,300 and 2,000 mg l −1 total substrates (equal concentrations of each phenolic) to a preinoculated bioreactor. At these levels, no cell growth and no degradation were observed; however, after adding polymer beads to the systems, the ensuing reduced substrate concentrations permitted complete destruction of the target molecules, demonstrating the essential role played by the polymer sequestering phase when applied to systems facing inhibitory substrate concentrations. In addition to establishing alternative modes of TPPB operation, the present work has demonstrated the differential partitioning of phenols in a mixture between the aqueous and polymeric phases. The polymeric phase was also observed to absorb a degradation intermediate (arising from the incomplete biodegradation of 4CP), which opens the possibility of using solid-liquid TPPBs during biosynthetic transformation to sequester metabolic byproducts.
Environmental Science & Technology, 2009
The present study has demonstrated the enhanced performance of a two-phase bioreactor, operating with polymers as a partitioning phase, as an alternative to both single phase biotreatment and to the use of an immiscible organic solvent partitioning phase, to deliver a toxic substrate (4-nitrophenol, or 4NP) to a microbial consortium in batch and repeated batch mode. Three commercial polymers were tested, Hytrel, Tone, and Elvax, and were shown to have superior properties related to the use of a consortium, including complete biocompatibility with the biomass and nonbiodegradability. Repeated kinetic tests performed with short reaction times demonstrated the accumulation of 4NP within the polymers in the range of 6-8 mg/g polymer, which reduced polymer performance in subsequent batch operations. Hytrel gave the best performance with residuals of up to 4 mg /g polymer showing no reduction in subsequent use, while for the other polymers a 4NP value lower than 2 mg/g polymer was required to have acceptable performance during repeated polymer use. Polymer reuse without affecting the process efficiency was confirmed with regeneration tests. A conventional methanol extraction method, as well as biological regeneration of the polymers by prolonged contact with the biomass, were assessed for their ability to remove the residual 4NP. Parallel kinetic tests performed with new and regenerated polymers showed a complete overlap of the 4NP concentration profiles indicating that a simple biological regeneration method provides a means of completely restoring polymer performance for repeated batch operation.
Degradation of xenobiotics in a partitioning bioreactor in which the partitioning phase is a polymer
Biotechnology and Bioengineering, 2003
Two-phase partitioning bioreactors (TPPBs) are characterized by a cell-containing aqueous phase and a second immiscible phase that contains toxic and/or hydrophobic substrates that partition to the cells at subinhibitory levels in response to the metabolic demand of the organisms. To date, the delivery phase in TPPBs has been a hydrophobic solvent that traditionally needed to possess a variety of important properties including biocompatibility, nonbioavailability, low volatility, and low cost, among others. In the present work we have shown that the organic solvent phase can be replaced by inexpensive polymer beads that function in a similar fashion as organic solvents, delivering a toxic substrate to cells based on equilibrium considerations. Specifically, 3.4 mm diameter beads of poly(ethylene-co-vinyl acetate) (EVA) were used to reduce the aqueous concentration of phenol in a bioreactor from toxic levels (~2,000 mg/L) to subinhibitory levels (~750 mg/L), after which Pseudomonas putida ATCC 11172 was added to the system and allowed to consume the total phenol loading. Thus, the beads absorbed the toxic substrate and released it to the cells on demand. The EVA beads, which could be reused, were able to absorb 14 mg phenol/g EVA. This work has opened the possibility of using widely mixed cultures in TPPB systems without concern for degradation of the delivery material and without concern of contamination. B 2003 Wiley Periodicals. Biotechnol Bioeng 84: 399 -405, 2003
New Biotechnology, 2012
The applicability of a sequencing batch two phase partitioning bioreactor (TPPB) to the biodegradation of a highly toxic compound, 2,4-dichlorophenol (DCP) (EC 50 = 2.3-40 mg L À1) was investigated. A kinetic study of the individual process steps (DCP absorption into the polymer, desorption and biodegradation) was performed and, based on favourable absorption/desorption characteristics (DCP diffusivity of 6.6 Â 10 À8 cm 2 s À1), the commercial polymer Tone P787 (Dow Chemical), was utilized as the sequestering phase for TPPB operation. Batch kinetic biodegradation tests were performed in both singleand two-phase modes, and the Haldane equation kinetic parameters were estimated (k = 1.3 Â 10 À2 mgDCP mgVSS À1 h À1 , K I = 35 mgDCP L À1 and K s = 18 mgDCP L À1), confirming the highly toxic nature of DCP. Consistent with these findings, operation of the single-phase system showed that for an initial DCP concentration of 130 mg L À1 the biomass was completely inhibited and DCP was not degraded, while the two-phase system achieved near-complete DCP removal. In sequencing batch mode the TPPB had a removal efficiency of 91% within 500 min for a feed of 320 mg L À1 , which exceeds the highest concentration previously degraded. These results have confirmed the effectiveness of the use of small amounts (5%, v/v) of inexpensive commercial polymers as the partitioning phase in TPPB reactors for the treatment of a highly toxic substrate at influent loads that are prohibitive for conventional singlephase operation, and suggest that similar detoxification of wastewater influents is achievable for other target cytotoxic substrates.
Biodegradation, 2005
Two phase partitioning bioreactors (TPPBs) operate by partitioning toxic substrates to or from an aqueous, cell-containing phase by means of second immiscible phase. Uptake of toxic substrates by the second phase effectively reduces their concentration within the aqueous phase to sub-inhibitory levels, and transfer of molecules between the phases to maintain equilibrium results in the continual feeding of substrate based on the metabolic demand of the microorganisms. Conventionally, a single pure species of microorganism, and a pure organic solvent, have been used in TPPBs. The present work has demonstrated the benefits of using a mixed microbial population for the degradation of phenol in a TPPB that uses solid polymer beads (comprised of ethylene vinyl acetate, or EVA) as the second phase. Polymer modification via an increase in vinyl acetate concentration was also shown to increase phenol uptake. Microbial consortia were isolated from three biological sources and, based on an evaluation of their kinetic performance, a superior consortium was chosen that offered improved degradation when compared to a pure strain of Pseudomonas putida ATCC 11172. The new microbial consortium used within a TPPB was capable of degrading high concentrations of phenol (»2000 mg l)1), with decreased lag time (10 h) and increased specific rate of phenol degradation (0.71 g phenol g)1 cell h). Investigation of the four-member consortium showed that it consisted of two Pseudomonas sp., and two Acinetobacter sp., and tests conducted upon the individual isolates, as well as paired organisms, confirmed the synergistic benefit of their existence within the consortium. The enhanced effects of the use of a microbial consortium now offer improved degradation of phenol, and open the possibility of the degradation of multiple toxic substrates via a polymer-mediated TPPB system.
Biotechnology Letters, 2012
In this paper the performance of two phase liquid-solid systems applied to the removal of xenobiotics was investigated. 4-nitrophenol, a typical representative of substituted phenols, was chosen as the target compound. Three polymers, a polyether-ester copolymer Hytrel 8206, a poly-caprolactone polyester Tone P797 and a polyethylenevinyl acetate copolymer Elvax were utilized in batch kinetic tests. The best performance was obtained with Hytrel, and this polymer was also employed as the partitioning phase in a lab scale sequencing batch reactor. In all cases in the two phase systems, even if operated with a very low polymer content (~ 5%), the biomass was exposed to 4nitropheol concentrations that are significantly lower if compared to the one-phase aqueous system with consequent drastic reduction of the toxic effect of 4-nitrophenol, and of the reaction times. A process model was also set up and applied to analyze the performance of the system in different operating conditions.
Polymer Selection for Biphenyl Degradation in a Solid-Liquid Two-Phase Partitioning Bioreactor
Biotechnology Progress, 2007
The commercially available thermoplastic polymer Hytrel was selected as the delivery phase for the hydrophobic model compound biphenyl in a solid-liquid two-phase partitioning bioreactor (TPPB), and 2.9 g biphenyl could successfully be degraded in 1-L TPPBs by a pure culture of the biphenyl-degrading bacterium Burkholderia xenoVorans LB400 in 50 h and by a mixed microbial consortium isolated from contaminated soil in 45 h. TPPBs consist of an aqueous cell-containing phase and an immiscible second phase that partitions toxic and/or poorly soluble substrates (in this case biphenyl) on the basis of maintaining a thermodynamic equilibrium. This paper illustrates a rational strategy for selecting a suitable solid polymeric substance for the delivery of the poorly water-soluble model compound biphenyl. The partitioning of biphenyl between the selected polymers and water was analogous to partitioning of solutes between two immiscible liquid phases. The partitioning coefficients varied between 180 for Nylon 6.6 and 11,000 for Desmopan, where the later numerical value is comparable to biphenyl partitioning coefficients between water and organic solvents. Employing a solid delivery phase enabled the utilization of a surfactant-producing microbial mixed culture, which could not be cultivated in liquid-liquid TPPBs and thereby extended the range of biocatalysts that can be employed in TPPBs.
Water Science and Technology, 2010
In this paper, a comparison is provided between liquid-liquid and liquid-solid partitioning systems applied to the removal of high concentrations of 4-nitrophenol. The target compound is a typical representative of substituted phenols found in many industrial effluents while the biomass was a mixed culture operating as a conventional Sequencing Batch Reactor and acclimatized to 4-nitrophenol as the sole carbon source. Both two-phase systems showed enhanced performance relative to the conventional single phase bioreactor and may be suitable for industrial application. The best results were obtained with the polymer Hytrel™ which is characterized by higher partition capability in comparison to the immiscible liquid solvent (2-undecanone) and to the polymer Tone™. A model of the two systems was formulated and applied to evaluate the relative magnitudes of the reaction, mass transfer and diffusion characteristic times. Kinetic parameters for the Haldane equation, diffusivity and mass tr...