Practical application of aqueous two‐phase systems for the development of a prototype process for c‐phycocyanin recovery from Spirulina maxima

A novel process for the recovery of c‐phycocyanin from Spirulina maxima exploiting aqueous two‐phase systems (ATPS), ultrafiltration and precipitation was developed in order to reduce the number of unit operations and benefit from an increased yield of the protein product. The evaluation of system parameters such as PEG molecular mass, concentration of PEG as well as salt, system pH and volume ratio was carried out to determine under which conditions the c‐phycocyanin and contaminants concentrate to opposite phases. PEG1450–phosphate ATPS proved to be suitable for the recovery of c‐phycocyanin because the target protein concentrated in the top phase whilst the cell debris concentrated in the bottom phase. A two‐stage ATPS process with a phase volume ratio (V_r) equal to 0.3, PEG1450 7% (w/w), phosphate 20% (w/w) and system pH of 6.5 allowed c‐phycocyanin recovery with a purity of 2.4 (estimated as the relationship of the 620 nm to 280 nm absorbances). The use of ultrafiltration (with a 30 kDa membrane cut‐off) and precipitation (with ammonium sulfate) resulted in a recovery process that produced a protein purity of 3.8 ± 0.1 and an overall product yield of 29.5% (w/w). The results reported here demonstrated the practical implementation of ATPS for the design of a prototype recovery process as a first step for the commercial purification of c‐phycocyanin produced by Spirulina maxima. © 2001 Society of Chemical Industry     

Application of Aqueous Two‐Phase Systems for the Potential Extractive Fermentation of Cyanobacterial Products

The potential use of aqueous two‐phase systems (ATPS) to establish a viable protocol for the in situ recovery of cyanobacterial products was evaluated. The evaluation of system parameters such as poly (ethylene glycol) (PEG) molecular mass, concentration of PEG and salt was carried out to determine the conditions under which Synechocystis sp. PCC 6803 cell and cyanobacterial products, i.e., β‐carotene and lutein, become concentrated in opposite phases. PEG‐phosphate ATPS proved to be unsuitable for the recovery of cyanobacterial products due to the negative effect of the salt upon the cell growth. The use of ATPS PEG‐dextran (6.6 % w/w PEG 3350, 8.4 % w/w dextran 66900, TLL 17.3 % w/w, V_R 1.0, pH 7) and (4.22 % w/w PEG 8000, 9.77 % w/w dextran 66900, TLL 18 % w/w, V_R 1.0, pH 7) resulted in the growth of cyanobacteria (Synechocystis sp. PCC 6803) and the concentration of lutein in opposite phases. However, β‐carotene was seen to concentrate in the top phase together with the biomass. The results reported here demonstrate the potential application of ATPS to establish the conditions for an extractive fermentation prototype process for the recovery of cyanobacterial products.     

Improved recovery of B‐phycoerythrin produced by the red microalga Porphyridium cruentum

A simplified process for the primary recovery and purification of B‐phycoerythrin (BPE) from Porphyridium cruentum exploiting aqueous two‐phase systems (ATPS) and isoelectric precipitation was developed in order to reduce the number of unit operations and benefit from increased purity and yield of the protein product. Evaluation of the partitioning behaviour of BPE in polyethylene glycol (PEG)/sulphate, PEG/dextran and PEG/phosphate ATPS was carried out to determine under what conditions the BPE and contaminants concentrated into opposite phases. An additional stage of isoelectric precipitation at pH 4.0 after cell disruption resulted in an increase in purity of the target protein from the BPE crude extract and enhanced the performance of the subsequent ATPS. PEG1000/phosphate ATPS proved to be suitable after isoelectric precipitation for the recovery of highly purified (defined as absorbance ratio A_{545 nm}/A_{280 nm} > 4.0) BPE with a potential commercial value as high as US$ 50/mg. An ATPS extraction stage comprising 29.5% (w/w) PEG1000, 9.0% (w/w) phosphate, a volume ratio (V_r) equal to 1.0, a system pH of 7.0 and loaded with 40% (w/w) of the BPE extract generated by precipitation allowed BPE recovery with a purity of 4.1±0.2 and an overall product yield of 72% (w/w). The purity of BPE from the crude extract increased 5.9‐fold after isoelectric precipitation and ATPS. The results reported herein demonstrate the benefits of the practical application of isoelectric precipitation together with ATPS for the recovery and purification of BPE produced by P. cruentum as a first step in the development of a commercial purification process. Copyright © 2006 Society of Chemical Industry     

酶法合成头孢氨苄的反应-双水相萃取耦合过程

应用聚乙二醇(PEG)/硫酸镁双水相体系(ATPS)进行了酶法合成头孢氨苄的反应-双水相萃取的耦合过程研究.通过考察头孢氨苄、苯甘氨酸甲酯和7-氨基脱乙酰氧基头孢烷酸(7-ADCA)在ATPS中的分配行为建立了一个含20％(质量)PEG 400和12％(质量)硫酸镁的ATPS,在此体系中头孢氨苄的分配系数为6.7,苯甘氨酸甲酯的分配系数为1.5,7-ADCA的分配系数为1.2,且青霉素酰化酶的分配系数小于0.01.底物、产物以及催化剂的分配特性有利于构建双水相体系应用于酶法合成头孢氨苄的反应-双水相萃取的耦合过程.对此双水相体系中青霉素酰化酶的稳定性研究表明催化剂亦适合此体系的构建.进而将此体系应用于头孢氨苄酶法合成,产率为60％左右,相对水相体系20％左右的产率取得了较好的结果.     

Aqueous two‐phase systems for the recovery of a recombinant viral coat protein from Escherichia coli

In this study the use of an aqueous two‐phase system (ATPS) following the direct chemical extraction of a recombinant viral coat protein, from the cytoplasm of Escherichia coli, is evaluated. The driving force is the need to establish an economically‐viable process for the manufacture of a vaccine against human papilloma infection. The partition behaviour of recombinant L1 protein, the major structural protein of the virus, and DNA was investigated in a polyethylene glycol (PEG)–phosphate system. An evaluation of system parameters including PEG molecular mass and the concentrations of PEG and phosphate was conducted, to estimate conditions under which the L1 protein and DNA partition to opposite phases. ATPS extraction comprising a volume ratio of 1.00, PEG 1000 (18.0%(w/w)) and phosphate (15.0%(w/w)) provided the conditions for accumulation of DNA into the bottom phase and concentration of L1 protein into the opposite phase (ie partition coefficient of DNA; ln K_DNA < 0.0 and partition coefficient of L1; ln K_L1 > 2.5). The findings reported here demonstrate the potential of ATPS to recover recombinant protein released from E coli by direct chemical extraction. © 2002 Society of Chemical Industry     

Potential application of aqueous two‐phase systems for the fractionation of RNase A and α‐Lactalbumin from their PEGylated conjugates

BACKGROUND: PEGylation reactions often result in a heterogeneous population of conjugated species and unmodified proteins that presents a protein separations challenge. Aqueous two‐phase systems (ATPS) are an attractive alternative for the potential fractionation of native proteins from their PEGylated conjugates. The present study characterizes the partition behaviors of native RNase A and α‐Lac and their mono and di‐PEGylated conjugates on polyethylene glycol (PEG)—potassium phosphate ATPS. RESULTS: A potential strategy to separate unreacted native protein from its PEGylated species was established based upon the partition behavior of the species. The effect of PEG molecular weight (400–8000 g mol^?1), tie‐line length (15–45% w/w) and volume ratio (V_R; 0.33, 1.00 and 3.00) on native and PEGylated proteins partition behavior was studied. The use of ATPS constructed with high PEG molecular weight (8000 g mol^?1), tie‐line lengths of 25 and 35% w/w, and V_R values of 1.0 and 3.0 allowed the selective fractionation of native RNase A and α‐Lactalbumin, respectively, from their PEGylated conjugates on opposite phases. Such conditions resulted in an RNase A bottom phase recovery of 99%, while 98% and 88% of mono and di‐PEGylated conjugates, respectively were recovered at the top phase. For its part, α‐Lac had a bottom phase recovery of 92% while its mono and di‐PEGylated conjugates were recovered at the top phase with yields of 77% and 76%, respectively. CONCLUSIONS: The results reported here demonstrate the potential application of ATPS for the fractionation of PEGylated conjugates from their unreacted precursors. Copyright © 2010 Society of Chemical Industry     

Extraction of microbial transglutaminase from <Emphasis Type="Italic">Amycolatopsis</Emphasis> sp. fermentation broth using aqueous two-phase system

Partitioning of microbial transglutaminase (MTG) from Amycolatopsis sp. in the polyethylene glycol (PEG)/salt-based ATPS was investigated for the first time. The key parameters such as the molecular weight of PEG (PEG 600-6000), the type and concentration of phase-forming salt (ammonium sulfate or phosphates), the pH of system (pH 5.0-8.5), and the concentration of neutral salt (0-6% NaCl, w/w) were determined. The partition coefficient of the enzyme was not linear with PEG molecular weight; PEG1000 gave better yield than others. The concentration of PEG1000, ammonium sulfate and NaCl, and the system pH showed effects with different extents on specific activity (SA) and yield of the enzyme. In the ATPS of 26% w/w PEG 1000 and 19% w/w ammonium sulfate in the presence of 5% w/w NaCl and at pH 6.0, MTG was partitioned into the PEG-rich phase with a maximum yield of 86.51% and SA was increased to 0.83. The results of SDS-PAGE showed the MTG produced by the test strain differed from the enzymes reported before. Thus, this study proves that ATPS can be used as a preliminary step for partial purification of MTG from Amycolatopsis sp. fermentation broth.     

New aqueous two‐phase systems based on poly(ethylene oxide sulfide) (PEOS) and potassium phosphate for the potential recovery of proteins

A new aqueous two‐phase system (ATPS) based on a degradable polymer called poly(ethylene oxide sulfide) with a molecular weight of 33 000 g mol^?1 (identified as PEOS‐12) and potassium phosphate was exploited for the potential recovery of proteins. An initial characterisation of the ATPS was achieved by the construction of a phase diagram for the PEOS‐12/phosphate system. The protein partitioning behaviour of lysozyme and bovine serum albumin (BSA), selected as single model proteins, and B‐phycoerythrin (BPE) produced by Porphyridium cruentum in the new ATPS under increasing tie line length (TLL) conditions at constant phase volume ratio (V_r) and system pH was investigated. Both single proteins partitioned in the new ATPS, initially exhibiting bottom phase preference; however, lysozyme changed phase preference when TLL was increased. Fractionation of a complex model (production of BPE by P. cruentum) using PEOS‐12/phosphate ATPS was performed to evaluate the potential protein recovery from fermentation broth or cell homogenate. The proposed new ATPS proved to be suitable for the potential recovery of BPE from crude extract of P. cruentum. In general, a system comprising V_r = 1.0, 18% (w/w) PEOS‐12, 8% (w/w) phosphate and 30% (w/w) TLL at pH 7.0 provided conditions to concentrate BPE into the bottom phase (i.e. partitioning behaviour of BPE; lnK_BPE = ?1.8) with a protein recovery of 84%. The findings reported here demonstrate the potential application of the new ATPS for the recovery of proteins from complex biological suspensions. Copyright © 2006 Society of Chemical Industry     

Synthesis and Surface Active Properties of tri[(N‐alkyl‐N‐ethyl‐N‐Sodium carboxymethyl)‐2‐Ammonium bromide ethylene] Amines

Trimeric betaine surfactants tri[(N‐alkyl‐N‐ethyl‐N‐sodium carboxymethyl)‐2‐ammonium bromide ethylene] amines were prepared with raw materials containing tris(2‐aminoethyl) amine, alkyloyl chloride, lithium aluminium hydride, sodium chloroacetate, and bromoethane by alkylation, Hoffman degradation reaction, carboxymethylation and quaternary amination reaction. The chemical structures of the prepared compounds were confirmed by FTIR, ¹H NMR, MS and elemental analysis. With the increasing length of the carbon chain, the values of their critical micelle concentration initially decreased. Surface active properties of these compounds were superior to general carboxylate surfactants C₁₀H₂₁CHN⁺(CH₃)₂COONa. The minimum cross‐sectional area per surfactant molecule (A_min), standard Gibbs free energy adsorption (ΔG_ads) and standard Gibbs free energy micellization (ΔG_mic) are notably influenced by the chain length n, and the trimeric betaine surfactants have greater ability to adsorb at the air/water interface than form micelles in solution. The efficiency of adsorption at the water/air interface (pC₂₀) of these surfactants increased with the increasing length of the alkyl chain. Their foaming properties, wetting ability of a felt chip, and lime‐soap dispersing ability were also investigated.     

Preparation and properties of water‐soluble polyester surfactants. I. Preparation and surface activity of poly(ethylene glycol)‐dimethyl 5‐sulfo‐isophthalate sodium salt polyester surfactants

The reaction of poly(ethylene glycol) (PEG, number‐average molecular weight M_n = 400‐2000) and dimethyl 5‐sulfoisophthalate sodium salt (SIPM) synthesized a series of anionic polymeric surfactants having a range of molecular weights. ¹H‐NMR, FTIR, and elemental analysis were employed to characterize the structures of these compounds. Also, the influences of the PEG segment lengths of PEG/SIPM copolymers on the surface tension, foaming properties, wetting power, and dispersant properties were investigated. The experimental results indicated that the solution that contained the PEG/SIPM copolymer surfactants exhibited excellent surface‐active properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2727–2731, 2002     

Extractive bioconversion of xylan for production of xylobiose and xylotriose using a PEG6000/sodium citrate aqueous two-phase system

Aqueous two-phase system (ATPS) was applied for extraction bioconversion of xylan by xylanase from Trichoderma viride. Phase diagrams for poly (ethylene glycol) (PEG) and sodium citrate were determined at room temperature. The ATPS composed of 12.99% (w/w) PEG6000 and 12.09% (w/w) sodium citrate was favorable for partition of xylanase and used for extraction bioconversion of xylan. Batch hydrolysis demonstrated that higher concentrations of xylobiose and xylotriose were obtained in the PEG6000/sodium citrate ATPS compared to those in the aqueous system. These results present the potential feasibility of production of xylo-oligosaccharides by extraction bioconversion in ATPS.     

Corrosion inhibition by N‐(alkyloxycarbonylmethyl)‐N‐triethanol ammonium chloride with respect to the surface and thermodynamic properties

N‐[(octyloxycarbonylmethyl)‐ N‐triethanol ammonium chloride] (C₈ ), N ‐[(dodecyl‐oxycarbonylmethyl)‐ N‐triethanol ammonium chloride] (C₁₂ ) and N ‐[(hexadecyloxycarbonylmethyl)‐N ‐triethanol ammonium chloride] (C₁₆ ) were synthesized. Surface tension was measured in aqueous solution for different concentrations at 28, 38 and 48°C. Various surface properties of the synthesized surfactants were evaluated, particularly critical micelle concentration (CMC), efficiency (Π_CMC) as well as maximum surface excess (Γ_max) and minimum surface area (A_min). Micellization and adsorption in both liquid/air and liquid/solid interfaces thermodynamics were investigated. These products have pronounced surface activity and satisfactory corrosion inhibition of C‐steel in hydrochloric acid at 28, 38 and 48°C. © 1999 Society of Chemical Industry     

The optimization of aqueous two‐phase extraction of lysozyme from crude hen egg white using response surface methodology

BACKGROUND: Aqueous two‐phase extraction is a versatile method for separating biological particles and macromolecules. In the present wok, the feasibility of using PEG 4000/potassium citrate aqueous two‐phase system (ATPS) for recovering and purifying lysozyme was investigated. Response surface methodology was used to determine an optimized ATPS for purification of lysozyme from crude hen egg white. RESULTS: Mathematical models concerning the purification of lysozyme from chicken egg white in polyethylene glycol 4000 (PEG 4000)/potassium citrate ATPS are established using response surface methodology. Screening experiments using fractional factorial designs show that the pH of the system significantly affects the recovery and purification of lysozyme. An optimized ATPS was proved to be at pH 5.5 and 30 °C and contained 18% (w/w) PEG, 16% (w/w) potassium citrate, 3.75% (w/w) potassium chloride (KCl). Under those conditions, the specific activity, purification factor and activity yield for lysozyme were 31100 U mg^?1, 21.11 and 103%, respectively. CONCLUSION: The PEG 4000/potassium citrate ATPS has the potential to be applied to establish bioprocesses for the primary recovery and partial purification of lysozyme. © 2012 Society of Chemical Industry     

Processing of soybean (Glycine max) extracts in aqueous two‐phase systems as a first step for the potential recovery of recombinant proteins

BACKGROUND: The potential use of plants as production systems to establish bioprocesses has been established over the past decade. However, the lack of efficient initial concentration and separation procedures affect the generic acceptance of plants as economically viable systems. In this context the use of aqueous two‐phase systems (ATPS) can provide strategies to facilitate the adoption of plants as a base for bioprocesses. Among the crops, soybeans (Glycine max) represent an attractive alternative since potentially they can produce high levels of recombinant protein. In this paper the processing of fractionated soybean extracts using ATPS is evaluated as a first step to recover recombinant proteins expressed in plants, using β‐glucuronidase (GUS; E.C. 3.2.1.31) as a model protein. RESULTS: The evaluation of the effect of system parameters provided the conditions under which the contaminant proteins from fractionated soybean extracts and GUS concentrated in opposite phases. A PEG 600/phosphate system comprising 14.5% (w/w) polyethylene‐glycol (PEG), 17.5% (w/w) phosphate, a volume ratio (Vr) equal to 1.0, and a system pH of 7.0 resulted in the potential 83% recovery of GUS from the complex mixture and an increase in purity of 4.5‐fold after ATPS. CONCLUSIONS: The findings reported here demonstrate the potential of ATPS to process fractionated soybean extract as a first step to isolate and purify a recombinant protein expressed in soybeans. The proposed approach can simplify the way in which recombinant proteins expressed in plants can be recovered. Copyright © 2007 Society of Chemical Industry     

Characteristics of poly(AAc5‐co‐HPMA3‐cl‐EGDMA15) hydrogel‐immobilized lipase of Pseudomonas aeruginosa MTCC‐4713

Four series of noble networks were synthesized with acrylic acid (AAc) copolymerized with varying amount of 2‐hydroxy propyl methacrylate or dodecyl methacrylate (AAc/HPMA or AAc/DMA; 5:1 to 5:5, w/w) in the presence of ethylene glycol dimethacrylate (EGDMA; 1, 5, 10, 15, and 20%, w/w) as a crosslinker and ammonium per sulfate (APS) as an initiator. Each of the networks was used to immobilize a purified lipase from Pseudomonas aeruginosa MTCC‐4713. The lipase was purified by successive salting out with (NH₄)₂SO₄, dialysis, and DEAE anion exchange chromatography. Two of the matrices, E_15a, i.e. [poly (AAc₅‐co‐DMA₁‐cl‐EGDMA₁₅)] and I_15c, i.e. [poly (AAc₅‐co‐HPMA₃‐cl‐EGDMA₁₅)], that showed relatively higher binding efficiency for lipase were selected for further studies. I_15c‐hydrogel retained 58.3% of its initial activity after 10th cycle of repetitive hydrolysis of p‐NPP, and I_15c was thus catalytically more stable and efficient than the other matrix. The I_15c‐hydrogel‐immobilized enzyme showed maximum activity at 65°C and pH 9.5. The hydrolytic activity of free and I_15c‐hydrogel‐immobilized enzyme increased profoundly in the presence of 5 mM chloride salts of Hg²⁺, NH₄⁺, Al³⁺, K⁺, and Fe³⁺. The immobilized lipase was preferentially active on medium chain length p‐nitrophenyl acyl ester (C:8, p‐nitrophenyl caprylate). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4636–4644, 2006     

Recovery of value‐added globular proteins from tannery wastewaters using PEG – salt aqueous two‐phase systems

Leather processing involves discharge of high‐value soluble globular proteins in the wastewater. The recovery of value‐added products from the wastewaters is gaining more importance in the context of recovery of wealth from waste. The recovery of these globular proteins from tannery wastewater was selected as a practical model system to study the implementation of polyethylene glycol (PEG)‐sulfate aqueous two‐phase systems (ATPS). The partition coefficient of bovine serum albumin is comparable to that of soluble proteins from tannery wastewaters. The influence of concentration of polymer, salt, pH and temperature on the partitioning of soluble proteins from tannery wastewaters has been studied. The PEG6000 + sodium sulfate + water system provide better partitioning of these soluble proteins as compared to PEG6000 + ammonium sulfate system. The maximum protein recovery yield for PEG6000 + sodium sulfate + water system at 20 °C is 92.75%. The influence of temperature indicates the recovery of proteins from tannery wastewater to be better at lower temperature. The findings of these studies raise the potential application of ATPS processes for protein recovery from complex biological systems. Copyright © 2006 Society of Chemical Industry     

Constructing Gemini‐Like Surfactants with Single‐Chain Surfactant and Dicarboxylic Acid Sodium Salts

Construction of gemini‐like surfactants using the cationic single‐chain surfactant cetyltrimethylammonium bromide C₁₆H₃₃N(CH₃)₃Br₂ (CTAB) and the anionic dicarboxylic acid sodium salt NaOOC(CH₂)_n‐2COONa (C_nNa₂, n = 4, 6, 8, 10, 12) by way of non‐covalent interactions has been investigated by surface tension measurements, hydrogen‐1 nuclear magnetic resonance (¹H NMR) spectroscopy and isothermal titration microcalorimetry (ITC). The critical micelle concentrations (cmc) of the CTAB/C_nNa₂ mixtures are obviously lower than that of CTAB and strongly depend on the mixing ratio. Moreover, the cmc values of the CTAB/C_nNa₂ mixtures decrease gradually with an increasing methylene chain length of C_nNa₂, indicating hydrophobic interaction between the hydrocarbon chains of CTAB and C_nNa₂ facilitates micellization of the mixtures. In particular, the ITC curves and ¹H NMR spectra indicate that the binding ratio of CTAB to C_nNa₂, except C₄Na₂, is around 2:1, i.e., (CTAB)₂C_nNa₂. Additionally, CTAB/C_nNa₂ mixtures are soluble in a whole molar ratio and concentration ranges have been studied, even at the electrical neutralization point. Therefore, these results reveal that highly soluble gemini‐like surfactants are conveniently constructed with oppositely‐charged cationic single‐chain surfactants and dicarboxylic acid sodiums. In an attempt at improving the performance of surfactants this work provides guidance for choosing additives that form gemini‐like surfactants via an uncomplicated synthesis.     

Rheological Properties of Wormlike Micelles Formed in Aqueous Systems of 3‐Alkoxy‐2‐hydroxypropyl Trimethyl Ammonium Bromides in the Presence of Sodium Octanoate

The rheological properties of aqueous systems composed of each of the four homologous cationic surfactants (3‐alkoxy‐2‐hydroxypropyl trimethyl ammonium bromides, C_nHTAB, n = 12, 14, 16 and 18) in the presence of an anionic surfactant, sodium octanoate (SO), have been studied by using steady state and frequency sweep rheological measurements. The effects of surfactant concentration, hydrophobic chain length and temperature were investigated. In C₁₄HTAB solution, the viscosity shows shear thinning in the concentration range of C_C14HTAB >320 mmol/kg. Addition of SO promotes the micellar growth and results in the generation of wormlike micelles. Zero‐shear viscosity (η₀) of the binary surfactant system exhibits a maximum point in the investigated concentration range, suggesting the interaction between C₁₄HTAB and SO molecules is strongest at the optimal ratio of C₁₄HTAB with SO. The decrease in viscosity was attributed to be the transition from entangled wormlike micelles to branching micelles after the maximum point, cryo‐TEM images revealed the changes in the structure of the wormlike micelles.     

Effect of Polyoxyethylene Chain Length on the Physicochemical Properties of N,N‐Dimethyl‐N‐dodecyl Polyoxyethylene Amine Oxide Hybrid Surfactants (C12EOnAO,with n = 1–4)

In order to determine the structure‐performance relationship of nonionic‐zwitterionic hybrid surfactants, N,N‐dimethyl‐N‐dodecyl polyoxyethylene (n) amine oxides (C₁₂EO_nAO) with different polyoxyethylene lengths (EO_n, n = 1–4) were synthesized. For homologous C₁₂EO_nAO, it was observed that the critical micelle concentration (CMC), the maximum surface excess (Γ_m), CMC/C₂₀, and the critical micelle aggregation number (N_m,c) decreased on going from 1 to 4 in EO_n. However, there were concomitant increases in surface tension at the CMC (γ_CMC), minimum molecular cross‐sectional area (A_min), adsorption efficiency (pC₂₀), and the polarity ([I₁/I₃]_m) based on the locus of solubilization for pyrene. The values of log CMC and N_m,c decreased linearly with EO_n lengthening from 1 to 4, although the impact of each EO unit on the CMC of C₁₂EO_nAO (n = 1–4) was much smaller than that typically seen for methylene units in the hydrophobic main chains of traditional surfactants. Compared to the structurally related conventional surfactant N,N‐dimethyl‐N‐dodecyl amine oxide (C₁₂AO), C₁₂EO_nAO (n = 1–4) have smaller CMC, A_min, and CMC/C₂₀, but larger pC₂₀, Γ_m, and N_m,c with a higher [I₁/I₃]_m. This may be attributed to the moderately amphiphilic EO_n (n = 1–4) between the hydrophobic C₁₂ tail and the hydrophilic AO head group.     

Organic media selection for the extraction of β‐hydroxyisobutyric acid produced by microbial biotransformation

The aim of this work is to evaluate both the toxic effect of different organic media on the stereospecific oxidation of 2‐methyl‐1,3‐propanediol to R‐(−)‐β‐hydroxyisobutyric (HIBA) in two‐phase systems and the extraction ability and selectivity of these non‐water miscible phases. Apart from traditional solvents, specific organic acid‐complexing carriers like TOPO, TOA and Aliquat 336 dissolved in different diluents have been studied. Special interest has been focused on the effect of the concentration of the organic phase extractants and the pH of the aqueous phase on the extraction system. TOPO dissolved in isooctane enabled higher K_p values at lower concentrations to be attained and resulted in lower toxicity, but its extractive capacity is strongly dependent on the pH. Our results suggest that using a compromise pH value between optimum for bioconversion and extraction, TOPO dissolved in isooctane can be successfully used as an extractive phase for HIBA production in a two‐phase system. © 2000 Society of Chemical Industry