Single Aqueous Phase Research Articles

PEDOT-intercalated MnO2 layers as a high-performance cathode material for aqueous Zn-ion batteries

Manganese oxides are considered as a cathode material with great application potential for zinc ion batteries (ZIBs). However, low electron conductivity and slow ion diffusion rate are major limitations restricting their rate capacity and cycle stability. Herein, we creatively intercalated the conductive poly(3,4-ethylenedioxythiophene) into MnO2 layers (sample named PEDOT-MnO2) via a redox precipitation reaction occurring between KMnO4, MnSO4, and EDOT. We used a simpler and more environmentally friendly material preparation process than related studies. The reaction system was a single aqueous phase without organic solvents, and the reaction was carried out in a stirred solution at 0–4 °C for 6 h. The pre-intercalated PEDOT enlarges the spacing of the MnO2 layers and effectively improves the electrical conductivity of the material. In addition, the "structural pillar" effect of PEDOT acting between the layers stabilizes the crystal structure of MnO2. Thus, the optimized sample (PEDOT-MnO2-2) suggests a superior reversible capacity (344 mAh g−1 at 0.2 A g−1), a high-rate performance (121 mAh g−1 at 2 A g−1), and excellent stability (142 mAh g−1 even after 1500 cycles at 2.0 A g−1).

Significant Enhancement of 5-Hydroxymethylfural Productivity from D-Fructose with SG(SiO2) in Betaine:Glycerol-Water for Efficient Synthesis of Biobased 5-(Hydroxymethyl)furfurylamine.

5-Hydroxymethyl-2-furfurylamine (5-HMFA) as an important 5-HMF derivative has been widely utilized in the manufacture of diuretics, antihypertensive drugs, preservatives and curing agents. In this work, an efficient chemoenzymatic route was constructed for producing 5-(hydroxymethyl)furfurylamine (5-HMFA) from biobased D-fructose in deep eutectic solvent Betaine:Glycerol–water. The introduction of Betaine:Glycerol could greatly promote the dehydration of D-fructose to 5-HMF and inhibit the secondary decomposition reactions of 5-HMF, compared with a single aqueous phase. D-Fructose (200 mM) could be catalyzed to 5-HMF (183.4 mM) at 91.7% yield by SG(SiO2) (3 wt%) after 90 min in Betaine:Glycerol (20 wt%), and at 150 °C. E. coli AT exhibited excellent bio-transamination activity to aminate 5-HMF into 5-HMFA at 35 °C and pH 7.5. After 24 h, D-fructose-derived 5-HMF (165.4 mM) was converted to 5-HMFA (155.7 mM) in 94.1% yield with D-Ala (D-Ala-to-5-HMF molar ratio 15:1) in Betaine:Glycerol (20 wt%) without removal of SG(SiO2), achieving a productivity of 0.61 g 5-HMFA/(g substrate D-fructose). Chemoenzymatic valorization of D-fructose with SG(SiO2) and E. coli AT was established for sustainable production of 5-HMFA, which has potential application.

Effects of aqueous phase circulation and catalysts on hydrothermal liquefaction (HTL) of penicillin residue (PR): Characteristics of the aqueous phase, solid residue and bio oil

Hydrothermal liquefaction (HTL) is a promising thermochemical technology for the treatment of hazardous wastes such as penicillin residue (PR). For the treatment of aqueous waste produced by PR in the HTL process, aqueous phase circulation is an attractive solution, both environmentally and economically. The present study shows that aqueous phase circulation can promote the transfer of organic matter from the aqueous phase to bio–oil. The content of organic acids and alcohols in the aqueous phase decreased significantly, and the bio–oil yield and energy recovery efficiency also increased. Under non–catalytic conditions, the bio–oil yield increased from 26.09 wt% to 33.72 wt%. The use of Na2CO3 as a catalyst further improved the bio–oil yield. After a single aqueous phase circulation, the bio–oil yield increased to 34.63 wt%, and the energy recovery efficiency increased to 66.94%. Under catalytic hydrothermal conditions, the content of organic acids in the bio–oil was reduced using aqueous phase circulations, which improved the quality of the bio–oil. At the same time, the Na2CO3 catalyst promoted the hydrolysis of PR to form small molecule organic matter, inhibited the formation of coke, and reduced the content of carbon, hydrogen and oxygen in the solid residue. An increase of cycle times led to excessive accumulation of Na2CO3, which had a negative impact on the yield of bio–oil. Nitrogen–containing compounds in the bio–oil increased to a certain extent, which renders it necessary to consider denitrification treatments in the future. The work provides a useful reference for further research on the preparation of high quality bio–oil by PR hydrothermal liquefaction.

Membrane-electrode assembly electrolysis of CO2 to formate using indium nitride nanomaterials

A new mode of membrane-electrode assembly based electrolysis was adopted for efficient electrochemical reduction of carbon dioxide (CO2RR) to formate. InN-C nanomaterials were employed as the CO2RR electrocatalyst, which showed excellent catalytic activity and high selectivity to produce formate, because of nitridation to form more basic sites. In aqueous phase, the maximum Faradaic efficiency (FE) by InN-C for formate was 92.2 % at -0.9 V vs RHE, higher than that of In2O3-C catalyst. In MEA electrolysis, the maximum FE reached 92.5 % at the cell voltage of 2.96 V with formate partial current density of 60.1 mA cm−2. The increased reactivity was due to optimized gas-liquid biphase transport of CO2, which is quite limited in single aqueous phase.

A Robust Protocol for Extracting Aqueous Metabolites of High Lipid Sera

Background: With the increasing focus of metabolomic methods on obesityrelated diseases, it is important to consider how sample handling may need to be adapted for the high compositions of lipids that can occur in such subjects. Introduction: High-lipid (cloudy, milky appearances; a.k.a. lipemic) biofluids are common in very high BMI subjects. Organic extractions of biofluids are useful for removing protein backgrounds, inactivating capsid viruses, and yielding relatively stable samples with excellent spectroscopic characteristics. This work considered how acetonitrile extractions, which are widely used, perform on lipemic sera. Results: In this technical note, we report the observation and remediation of a liquid-liquid phase separation in acetonitrile extractions of many lipemic sera. This unexpected behavior can be challenging to identify, especially if working with small volumes. The liquid-liquid separation shows a high miscibility of proteins in both liquid phases that impairs NMR data quality. We also report a simple temperature-based adaption of the acetonitrile extraction procedure that consistently results in a single aqueous phase and eliminates unwanted constituents. Conclusion: A robust approach to achieving reproducible, high quality samples of aqueous metabolites from lipemic sera from very high BMI subjects should be of utility in expanding metabolomics applications to lipemic biofluids.

Light-Dependent and Aeration-Independent Gram-Scale Hydroxylation of Cyclohexane to Cyclohexanol by CYP450 Harboring Synechocystis sp. PCC 6803.

Oxygenase-containing cyanobacteria constitute promising whole-cell biocatalysts for oxyfunctionalization reactions. Photosynthetic water oxidation thereby delivers the required cosubstrates, that is activated reduction equivalents and O2 , sustainably. A recombinant Synechocystis sp. PCC 6803 strain showing unprecedentedly high photosynthesis-driven oxyfunctionalization activities is developed, and its technical applicability is evaluated. The cells functionally synthesize a heterologous cytochrome P450 monooxygenase enabling cyclohexane hydroxylation. The biocatalyst-specific reaction rate is found to be light-dependent, reaching 26.3 ± 0.6 U gCDW -1 (U = μmol min-1 and cell dry weight [CDW]) at a light intensity of 150 µmolphotons m-2 s-1 . In situ substrate supply via a two-liquid phase system increases the initial specific activity to 39.2 ± 0.7 U gCDW -1 and stabilizes the biotransformation by preventing cell toxification. This results in a tenfold increased specific product yield of 4.5 gcyclohexanol gCDW -1 as compared to the single aqueous phase system. Subsequently, the biotransformation is scaled from a shake flask to a 3 L stirred-tank photobioreactor setup. In situ O2 generation via photosynthetic water oxidation allows a nonaerated process operation, thus circumventing substrate evaporation as the most critical factor limiting the process performance and stability. This study for the first time exemplifies the technical applicability of cyanobacteria for aeration-independent light-driven oxyfunctionalization reactions involving highly toxic and volatile substrates.

Stabilization and scale-up of photosynthesis-driven ω-hydroxylation of nonanoic acid methyl ester by two-liquid phase whole-cell biocatalysis.

Photoautotrophic organisms are promising hosts for biocatalytic oxyfunctionalizations because they supply reduction equivalents as well as O2 via photosynthetic water oxidation. Thus far, research on photosynthesis-driven bioprocesses mainly focuses on strain development and the proof of principle in small-scale biocatalytic reaction setups. This study investigates the long-term applicability of the previously developed cyanobacterial strain Synechocystis sp. PCC 6803_BGT harboring the alkane monooxygenase system AlkBGT catalyzing terminal alkyl group oxyfunctionalization. For the regiospecific ω-hydroxylation of nonanoic acid methyl ester (NAME), this biocatalyst showed light intensity-independent hydroxylation activity and substantial hydrolysis of NAME to nonanoic acid. Substrate mass transfer limitation, substrate hydrolysis, as well as reactant toxicity were overcome via in situ substrate supply by means of a two-liquid phase system. The application of diisononyl phthalate as organic carrier solvent enabled 1.7-fold increased initial specific activities (5.6 ± 0.1 U/gCDW ) and 7.6-fold increased specific yields on biomass (3.8 ± 0.1 mmolH-NAME /gCDW ) as compared with single aqueous phase biotransformations. Finally, the whole-cell biotransformation system was successfully scaled from glass tubes to a stirred-tank photobioreactor. This is the first study reporting the application of the two-liquid phase concept for efficient phototrophic whole-cell biocatalysis.

Efficient Synthesis of Furfural from Biomass Using SnCl₄ as Catalyst in Ionic Liquid.

Furfural is a versatile platform molecule for the synthesis of various chemicals and fuels, and it can be produced by acid-catalyzed dehydration of xylose derived from renewable biomass resources. A series of metal salts and ionic liquids were investigated to obtain the best combination of catalyst and solvent for the conversion of xylose into furfural. A furfural yield of 71.1% was obtained at high xylose loading (20 wt%) from the single-phasic reaction system whereby SnCl4 was used as catalyst and ionic liquid 1-ethyl-3-methylimidazolium bromide (EMIMBr) was used as reaction medium. Moreover, the combined catalyst consisting of 5 mol% SnCl4 and 5 mol% MgCl2 also produced a high furfural yield (68.8%), which was comparable to the furfural yield obtained with 10 mol% SnCl4. The water–organic solvent biphasic systems could improve the furfural yield compared with the single aqueous phase. Although these organic solvents could form biphasic systems with ionic liquid EMIMBr, the furfural yield decreased remarkably compared with the single EMIMBr phase. Besides, the EMIMBr/SnCl4 system with appropriate water was also efficient to convert xylan and lignocellulosic biomass corn stalk into furfural, obtaining furfural yields as high as 57.3% and 54.5%, respectively.

Influence of Natural Solutes and Ionic Liquids on the Yield of Enzyme-Catalyzed Reactions: Measurements and Predictions

The maximum yield of enzyme-catalyzed reactions is often limited by thermodynamic equilibrium. The knowledge of influencing factors on limitations of reactions is essential for process optimization to increase yields and to reduce solvent and energy consumption. In this work the effect of solvents/cosolvents [e.g., ionic liquid (IL)] and natural solutes on thermodynamic yield limitations of two enzyme-catalyzed model reactions were investigated, namely, an alcohol dehydrogenase (ADH) reaction (acetophenone + 2-propanol ⇌ 1-phenylethanol + acetone) and an alanine aminotransferase reaction (l-alanine + 2-oxoglutarate ⇌ pyruvate + l-glutamate). Experimental results showed that the equilibrium position and the equilibrium product yield of both reactions in aqueous single-phase systems strongly depend on the type and molality of the present natural solute/IL that were present as additives in the reaction mixture. In addition, the ADH reaction was investigated in pure IL and in an IL/buffer two-phase system. Co...

Comparative effects of aqueous single-phase and oil-water two-phase mouthrinses containing bamboo salt, magnolia bark andCentella asiaticaextracts on reducing gingivitis: a randomized clinical trial

Objectives: The aim of this study was to assess the antiplaque and antigingivitis effectiveness of aque ous single-phase and oil-water two-phase mouthrinses, containing bamboo salt, magnolia bark, and Centella asiatica extracts, in Korean adults. Methods: In this double-blinded clinical trial, a total of thirty-four participants aged over 19 years were randomly allocated to three experimental groups: 1) control group; 2) aqueous single-phase mouthrinse (ASM) group, and; 3) oil-water two-phase mouthrinse (OTM) group. The experimental mouthrinses all contained sodium fluoride, and the ASM and OTM contained additional ingredients of bamboo salt, magnolia bark, and Centella asiatica extracts. For the OTM, 50% essential oil was added to create an oil-water two-phase mouthrinse. A two-week randomized crossover design with a two-week washout period was applied. Following a complete dental prophylaxis, participants were instructed to use the prescribed mouthrinse twice daily for two weeks as an adjunct to their usual mechanical oral hygiene procedures. Pre- and post-experiment clinical examinations were performed to measure the plaque index (PI) and bleeding on probing (BOP) for the full mouth. Paired t-test was applied to compare the intergroup differences for all clinical variables. Results: Compared to the control group, ASM showed a significantly reduced BOP (P<0.05). However, there was no statistically significant difference in the effects of the three mouthrinses on reducing the PI. Conclusions: The results of this study indicate that the use of an aqueous, single-phase mouthrinse containing bamboo salt, magnolia bark and Centella asiatica extracts could help alleviate gingivitis.

Enhancement of (S)-2,3-dichloro-1-propanol production by recombinant whole-cell biocatalyst in n-heptane–aqueous biphasic system

The enantioselective resolution of (R,S)-2,3-dichloro-1-propanol ((R,S)-DCP) to (S)-DCP by whole cells of a recombinant Escherichia coli expressing halohydrin dehalogenase (HHDH) activity was limited by product inhibition. To solve this problem to improve the productivity of (S)-DCP, an n-heptane–aqueous biphasic system was adopted in this work. The influential operational parameters including phase volumetric ratio, buffer pH and reaction temperature were optimized. Under the optimal reaction conditions, significant improvements of substrate concentration and biocatalyst productivity (375mM and 7.64mmol (S)-DCPg−1cell) were achieved in this n-heptane–aqueous biphasic system compared with aqueous single-phase system (150mM and 2.97mmolg−1cell). The scale-up biosynthesis of (S)-DCP was successfully performed in a 2-L stirred reactor, resulting in a 128.8mM (S)-DCP with enantiomeric excess of 99.1% and average productivity of 2.07g (S)-DCPL−1h−1, respectively.

Experimental study of trace element release during ultrahigh-pressure serpentinite dehydration

Subduction of serpentinite is envisaged to play a key role in volatile and element recycling at convergent plate margins, but there is currently little known about the composition of the fluid phase(s) released by devolatilisation of deeply subducted serpentinite. We have performed a series of ultrahigh pressure experiments to examine the phase relations and fluid compositions produced by reaction of a natural serpentinite under sub-arc conditions. We employ a novel technique of forming synthetic fluid inclusions in olivine at run conditions to preserve samples of experimental fluids for subsequent analysis. Our experiments confirm that the breakdown of antigorite and chlorite are the most important fluid-producing reactions from serpentinite at sub-arc depths. For our low CaO/Al2O3 peridotitic composition at 3.5 to 4.0 GPa we find that clinopyroxene reacts out below 750 °C and chlorite breaks down progressively between 700 and 800 °C to form garnet harzburgite.Raman analysis of synthetic fluid inclusions indicates that all experiments contained a single aqueous fluid phase, which – together with a lack of textural or mineralogical evidence for hydrous melting – indicates that the water-saturated solidus for our starting composition is above 900 °C at 4.0 GPa. Element concentrations in the fluid for three experiments were determined in situ via laser ablation ICP-MS of individual fluid inclusions. In general, the fluids are enriched in trace elements compared to the bulk starting material, but particularly so for Li, B, LILE, LREE, and U. Chlorite dehydration fluids have high Li/B, LREE/HREE and Ce/Y due to retention of some B in olivine, and retention of Y and HREE in garnet. Our results indicate that fluids produced by serpentinite dehydration at sub-arc depths may carry some of the slab-derived trace elements required for arc magmatism, and may fractionate key trace element ratios in the dehydrated residues, which in turn may ultimately contribute to the geochemical heterogeneity of mantle-derived magmas.

Biodegradation of microcrystalline cellulose in pH–pH recyclable aqueous two-phase systems with water-soluble immobilized cellulase

Product inhibition is a barrier for enzymatic conversion of cellulose into reducing sugar in single aqueous phase. In addition, the difficulty in the recovery of cellulase also leads to high cost for the enzymatic hydrolysis of cellulose. In this study, enzymatic degradation of cellulose was carried out in pH–pH recyclable aqueous two-phase systems (ATPS) composed by copolymers poly (AA-co-DMAEMA-co-BMA) (abbreviated PADB3.8) and poly (MAA-co-DMAEMA-co-BMA) (abbreviated PMDB). In the systems, cellulase was immobilized on pH-response copolymer PMDB by using 1-Ethyl-3-(3-dimethyllaminopropyl)-carbodiimide hydrochloride (EDC) as cross-linker. Optimized partition coefficient of product in the systems was 2.45, in the presence of 40mM (NH4)2SO4. Insoluble substrate and immobilized enzyme were biased to bottom phase, while the product was partitioned to top phase. Microcrystalline cellulose was hydrolyzed into reducing sugar, and the product entered into top phase. The yield of saccharification in ATPS could reach 70.57% at the initial substrate concentration of 0.5% (w/v), and the value was 9.3% higher than that in the single aqueous phase. Saccharification yield could reach 66.15% after immobilized cellulase was recycled five times in ATPS.

Whole‐cell‐based CYP153A6‐catalyzed (S)‐limonene hydroxylation efficiency depends on host background and profits from monoterpene uptake via AlkL

Living microbial cells are considered to be the catalyst of choice for selective terpene functionalization. However, such processes often suffer from side product formation and poor substrate mass transfer into cells. For the hydroxylation of (S)-limonene to (S)-perillyl alcohol by Pseudomonas putida KT2440 (pGEc47ΔB)(pCom8-PFR1500), containing the cytochrome P450 monooxygenase CYP153A6, the side products perillyl aldehyde and perillic acid constituted up to 26% of the total amount of oxidized terpenes. In this study, it is shown that the reaction rate is substrate-limited in the two-liquid phase system used and that host intrinsic dehydrogenases and not CYP153A6 are responsible for the formation of the undesired side products. In contrast to P. putida KT2440, E. coli W3110 was found to catalyze perillyl aldehyde reduction to the alcohol and no oxidation to the acid. Furthermore, E. coli W3110 harboring CYP153A6 showed high limonene hydroxylation activities (7.1 U g CDW-1). The outer membrane protein AlkL was found to enhance hydroxylation activities of E. coli twofold in aqueous single-phase and fivefold in two-liquid phase biotransformations. In the latter system, E. coli harboring CYP153A6 and AlkL produced up to 39.2 mmol (S)-perillyl alcohol L tot-1 within 26 h, whereas no perillic acid and minor amounts of perillyl aldehyde (8% of the total products) were formed. In conclusion, undesired perillyl alcohol oxidation was reduced by choosing E. coli's enzymatic background as a reaction environment and co-expression of the alkL gene in E. coli represents a promising strategy to enhance terpene bioconversion rates.

From a Water-Immiscible Monomer to Block Copolymer Nano-Objects via a One-Pot RAFT Aqueous Dispersion Polymerization Formulation

We describe the facile atom-efficient synthesis of diblock copolymer nano-objects via a one-pot RAFT aqueous dispersion polymerization protocol starting from a water-immiscible methacrylic monomer. More specifically, an aqueous emulsion of glycidyl methacrylate (GlyMA) is quantitatively converted into a 10% w/w aqueous solution of glycerol monomethacrylate (GMA) at 80 °C in air within 9 h in deionized water. 1H NMR spectroscopy studies indicate no evidence for either methacrylic ester hydrolysis or polymerization during this ring-opening reaction. Kinetic analysis indicates that a significant rate acceleration occurs as the reaction mixture switches from a two-phase emulsion to a single aqueous phase. This observation is fully consistent with the GlyMA–GMA–water ternary phase diagram determined at 80 °C. The 10% w/w aqueous solution of GMA can be polymerized using RAFT chemistry to produce a near-monodisperse PGMA macromolecular chain-transfer agent (macro-CTA), which indicates that relatively little dime...

Morphology and structure controlled synthesis of ruthenium nanoparticles in oleylamine

Mastery over the morphology/structure of nanoparticles enables control of their properties and enhancement of their usefulness for a given application. Herein, we report a systematic study on the synthesis of ruthenium nanoparticles in oleylamine, including the tuning of their morphology/shape by temperature or by seed-mediated growth. A phase-transfer based strategy for the fabrication of the Ru nanoparticles with hollow interiors has also been demonstrated in this work, which involves the phase transfer of the core-shell Ag-Ru nanoparticles prepared in oleylamine from organic solvent to aqueous phase and the subsequent removal of Ag cores from the core-shell nanoparticles by reacting with NaCl. This approach enables the synthesis of hollow structured Ru nanoparticles in a single aqueous phase, and avoids the use of expensive chemical reagents. Both of them are favorable for the large-scale synthesis of Ru nanoparticles with hollow interiors.

Conversion of Xylose to Furfural Using Lewis and Brønsted Acid Catalysts in Aqueous Media

The role of molecular structure on pentose dehydration to furfural has been examined using HCl as a Bronsted acid catalyst in a single phase aqueous media. It is shown that xylulose dehydration results in a much higher furfural yield than xylose dehydration under similar reaction conditions. Furthermore, a cascade of reactions for the efficient conversion of xylose to furfural in a single pot reactor is presented whereby a Lewis acid, CrCl3, is used to isomerize xylose to xylulose, and a Bronsted acid, HCl, is employed to dehydrate xylulose to furfural. Using the combination of Lewis and Bronsted acids, a furfural yield of ∼39% is achieved compared to ∼29% using HCl alone, at a moderate reaction temperature (∼418 K) in a single aqueous phase, with an associated decrease in the residence time by a factor of 5. With this combined catalyst functionalities, a much higher yield (76%) to furfural can be obtained in a biphasic system at low temperatures and short times. Aside from increasing performance, our res...

Biodegradation of cellulose in novel recyclable aqueous two-phase systems with water-soluble immobilized cellulase

Aqueous two-phase systems (ATPS) are an attractive technology in bioseparation engineering. However, one key problem is that phase-forming copolymer could not be recycled efficiently. This results in high cost and environmental pollution. In this study, we have developed recyclable aqueous two-phase systems composed by pH-response copolymer PMDB and thermo-response copolymer PNB and have carried out biodegradation of cellulose in the ATPS. The phase-forming copolymers could be recycled with over 95.0% recovery. In the systems, cellulase was immobilized on pH-response copolymer PMDB by using 1-ethyl-3-(3-dimethyllaminopropyl)-carbodiimide hydrochloride as cross-linker, and optimized partition coefficient of product was 3.68. Insoluble substrate and immobilized enzyme were biased in bottom phase, while product was partitioned in top phase. Microcrystalline cellulose was catalyzed into reducing sugar, then the product entering into the top phase. In the end, inhibition of product was removed, and the yield of reducing sugar in ATPS was increased 10.94% compared with the reaction in the single aqueous phase. The saccharification in ATPS could reach 40.16% when the reaction reached equilibrium.

Significantly improved asymmetric oxidation of sulfide with resting cells of Rhodococcus sp. in a biphasic system

Enantiopure sulfoxides can be prepared via the asymmetric oxidation of sulfides using sulfide monooxygenases. Five different organic–aqueous biphasic systems were investigated for their abilities to increase the bio-oxidation efficiency of a water-insoluble sulfide (phenyl methyl sulfide, PMS). Isooctane was found to be the most suitable organic phase solvent. In this isooctane–aqueous system, the oxidation reaction was not sensitive to pH, giving high yields over the entire range of the tested pH values (5.0–11.0). In contrast, cell concentration significantly affected the reaction rate. (S)-Phenyl methyl sulfoxide ((S)-PMSO) was formed at a higher concentration and a greater enantiomeric excess (18.3mM and >99.0% ee(S)) in this isooctane–aqueous biphasic system than in an aqueous single-phase system (2.17mM and 59.9% ee(S)). The asymmetric oxidation of 150mM PMS in the isooctane phase was successfully carried out in a mechanically stirred bioreactor (2.4L) and resulted in a 49.0% yield of (S)-PMSO with enantiomeric excess greater than 99.0%.

A strategic approach for the design and operation of two‐phase partitioning bioscrubbers for the treatment of volatile organic compounds

A strategic approach for the design of two-phase partitioning bioscrubbers (TPPBs) has been formulated using, as a basis, a re-evaluation of extensive literature data available for the degradation of benzene by Achromobacter xylosoxidans Y234 in TPPBs with n-hexadecane as the partitioning phase. Using a previously determined maintenance coefficient for benzene, we determined that an inlet benzene loading rate of 100 mg/h requires 5,928 mg cell mass at biological steady state and 243.0 mg O(2) /h. The total oxygen-transfer rates (TOTRs) into the TPPB increased by 83.5% with 33.3% of organic phase compared with a single aqueous phase and were significantly influenced by gas flow rate, whereas agitation has a minor affect. The fraction of organic phase used was suggested to be the primary parameter with which the TOTR into the TPPB may be altered. Although the presence of an organic solvent in the TPPB remarkably increased the TOTR, the total benzene transfer rate into the TPPB remained largely insensitive due to the intrinsic low Henry's law constant (or relatively high solubility) of benzene in water. Finally, we have integrated the elements of this analysis into a set of heuristic criteria that can serve as a guideline for the design of TPPB systems for future volatile organic compound treatment applications.