Cloud Point System Research Articles

In situ extraction of polar product of whole cell microbial transformation with polyethylene glycol‐induced cloud point system

A novel polyethylene glycol-induced cloud point system (PEG-CPS) was developed for in situ extraction of moderate polar product by setting a microbial transformation of benzaldehyde into L-phenylacetylcarbinol (L-PAC) with Saccharomyces cerevisiae (baker's yeast) as a model reaction. The biocompatibility of the microorganism in PEG-CPS was comparatively studied with a series of water-organic solvent two-phase partitioning systems. The tolerance of microorganism to the toxic substrate benzaldehyde was increased and the moderate polar product L-PAC was extracted into the surfactant-rich phase in the PEG-CPS. The novel PEG-CPS fills the gap of in situ extraction of polar product in microbial transformation left by water-organic solvent two-phase partitioning system. At the same time, the application of PEG-CPS in a microbial transformation also avoids expensive solvent when compared with that of aqueous two-phase system or CPS.

Cloud point extraction for cobalt preconcentration with on-line phase separation in a knotted reactor followed by ETAAS determination in drinking waters

A novel method for cobalt preconcentration by cloud point extraction with on-line phase separation in a PTFE knotted reactor and further determination by electrothermal atomic absorption spectrometry (ETAAS) is proposed. The cloud point system was formed in the presence of non-ionic micelles of polyethyleneglycolmono- p-nonylphenylether (PONPE 7.5) and it was retained on the inner walls of a knotted reactor (KR). The surfactant rich-phase was removed from the knotted reactor with 75 μL of methanol acidified with 0.8 mol L −1 nitric acid, directly into the dosing hole of the L’Vov graphite tube. An enrichment factor of 15 was obtained with a preconcentration time of 60 s, with respect to the direct determination of cobalt by ETAAS in aqueous solutions. The value of the detection limit for the preconcentration of 5 mL of sample solution was 10 ng L −1. The precision, expressed as the relative standard deviation (R.S.D.), for 10 replicate determinations at 0.5 μg L −1 Co level was 4.5%. Verification of the accuracy was carried out by analysis of a standard reference material (NIST SRM 1640e “Trace elements in natural water”). The method was successfully applied to the determination of cobalt in drinking water samples.

Whole cell microbial transformation in cloud point system

Cloud point system, consisting of nonionic surfactant in an aqueous solution, has been developed as a novel medium for whole cell microbial transformation. The basic properties of cloud point system including phase separation and solubilization are introduced. The application of cloud point system for extractive microbial transformation is different from that of water-organic solvent two-phase partitioning system or aqueous two-phase system are discussed, which mainly focus on the biocompatibility of microorganism in a cloud point system and a downstream process of microbial transformation in cloud point system with oil-water-surfactant microemulsion liquid-liquid extraction for surfactant recovery and product separation. Finally, examples of whole cell microbial transformation in cloud point systems, especially in situ extraction of moderate polar substrate/product, are also presented.

A downstream process with microemulsion extraction for microbial transformation in cloud point system

A downstream process strategy for a whole microbial transformation to produce l-phenylacetylcarbinol (PAC) in a nonionic surfactant Triton X mediated cloud point system was developed. By application of a Winsor I microemulsion, the product and the nonionic surfactant in the microbial transformation broth was separated successfully. Then the nonionic surfactant was recovered with a Winsor II microemulsion. In a single stage Winsor I microemulsion extraction process, the product recovery ratio 76.9% and the nonionic surfactant recovery ratio 66.5% were achieved. A discrete countercurrent extraction operation was also carried out to improve the separation efficiency. Finally, character of the recovery nonionic surfactant was also examined.

Production of l-phenylacetylcarbinol by microbial transformation in polyethylene glycol-induced cloud point system

Microbial transformation of benzaldehyde into L: -phenylacetylcarbinol by whole cell Saccharomyces cerevisiae has been carried out in a novel polyethylene glycol (PEG)-induced cloud point system. The system is composed of 80 g PEG 20,000, 75 ml Triton X-100, 20 g peptone, 10 g yeast extract, 25 g glucose, 1 g MgSO(4).7H(2)O, 0.05 g CaCl(2).2H(2)O, 35 g Na(2)HPO(4).12H(2)O, and 10.7 g citric acid per liter of tap water. The microbial transformation is conducted at 0.6 ml of acetaldehyde (35% volume content), 0.9 ml of benzaldehyde, and 7 g of wet cell per 100 ml of the PEG-induced cloud point system. Under the conditions, a relatively longer-term bioactivity of whole cell microorganism in the PEG-induced cloud point system has been achieved. A fed-batch microbial transformation process with a discrete addition of glucose and substrate gets a high final product concentration of about 8 g/l.

Improvement the tolerance of baker's yeast to toxic substrate/product with cloud point system during the whole cell microbial transformation

The industrial process of a whole-cell microbial transformation is usually hindered by the toxicity or inhibition of a high substrate/product concentration. Especially in a biocatalytic redox process, the cofactor regeneration with the viable cells is a key of the whole cell microbial transformation. In present work, growing culture of Saccharomyces cerevisiae (baker's yeast) in a nonionic surfactant mediated cloud point system was carried out. Then the tolerances of baker's yeast cells against a high substrate/product concentration and a long term of biocatalytic reduction of acetophenone to produce 1-phenylethanol as a model were examined in the cloud point system. The long term of cofactor regeneration at a high substrate concentration in the cloud point system make the cloud point system potential for further development as a novel two-phase partitioning system for production of chiral compounds by microbial transformation.

The potential of cloud point system as a novel two-phase partitioning system for biotransformation

Although the extractive biotransformation in two-phase partitioning systems have been studied extensively, such as the water-organic solvent two-phase system, the aqueous two-phase system, the reverse micelle system, and the room temperature ionic liquid, etc., this has not yet resulted in a widespread industrial application. Based on the discussion of the main obstacles, an exploitation of a cloud point system, which has already been applied in a separation field known as a cloud point extraction, as a novel two-phase partitioning system for biotransformation, is reviewed by analysis of some topical examples. At the end of the review, the process control and downstream processing in the application of the novel two-phase partitioning system for biotransformation are also briefly discussed.

Enzymatic hydrolysis of penicillin G to 6-aminopenicillanic acid in cloud point system with discrete countercurrent experiment

A set of flasks was utilized to simulate a discrete countercurrent bioreactor. An enzymatic hydrolysis of penicillin G to 6-aminopenicillanic acid with immobilized penicillin acylase in a cloud point system was carried out with the discrete countercurrent operational mode. Byproduct phenylacetic acid is effectively transported with the auxiliary phase (coacervate phase), while product 6-aminopenicillanic acid and reactant penicillin G are effectively transported with the aqueous phase, where the enzymatic hydrolysis of penicillin G takes place. The experimentally results show that the product concentration and product yield are improved from the batch operational mode of about 38 mM and 50% to the corresponding countercurrent operational mode of above 50 mM and 65%, respectively. However, experimentally examination of the effect of operational parameters, such as feed point location, volume ratio of auxiliary phase to aqueous phase and initial reactant concentration, indicates that the achievement of a high product concentration and a high product yield at the same time is difficult by a simple utilization of the continuous countercurrent operational mode. This can be contributed to the facts that the enzymatic hydrolysis favors at a relatively higher pH, but the extraction of PAA only takes place at a relatively lower pH.

Thermodynamic Equilibrium Control of the Enzymatic Hydrolysis of Penicillin G in a Cloud Point System without pH Control

A thermodynamic equilibrium model of the enzymatic hydrolysis of penicillin G to produce 6-aminopenicillanic acid in a cloud point system, a novel biphasic system for extractive biocatalysis, was developed. An extractive reaction coefficient was proposed to set up the relationship between the effect of the cloud point system to the enzymatic hydrolysis of penicillin G and the operation parameters, such as pH, phase volume ratio, and partitioning coefficients of reactants or products. On the basis of the model analysis, an experimental procedure of a discrete semibatch process was developed and a high product 6-aminopenicillanic acid concentration was achieved without pH control. This envisages an industrial application of the eco-friendly semibatch process with a recycle of the coacervate phase of the cloud point system.

An Eco-Friendly and Sustainable Process for Enzymatic Hydrolysis of Penicillin G in Cloud Point System

Enzymatic hydrolysis of penicillin G by immobilized penicillin acylase in a nonionic surfactant mediated cloud point system was presented. The effect of the operation parameters on equilibrium pH of this enzymatic hydrolysis process without pH control was examined. A relatively high equilibrium pH in cloud point system without pH control can be obtained. The feasibility of recycling utilization of the nonionic surfactant, a novel green solvent, was also investigated experimentally. Enzymatic hydrolysis of penicillin G in a discrete semi-batch mode, which simulates a semi-continuous process, envisages a completely eco-friendly, sustainable and efficient process for production of 6-aminopenicillanic acid.

Direct extraction of phenylacetic acid from immobilised enzymatic hydrolysis of penicillin G with cloud point extraction

AbstractThe enzymatic hydrolysis of potassium salt of penicillin G (Pen G) into phenylacetic acid (PAA) and potassium salt of 6‐aminopenicillanic acid (APA) is inhibited not only by the substrate and the product APA but also by the by‐product PAA. The partitioning behaviour of PAA in a cloud point system, a novel two‐phase partitioning system, was determined. Direct extraction of PAA in the process of immobilised penicillin acylase hydrolysis of Pen G without pH control was achieved. Pen G was hydrolysed almost completely and the product APA concentration in the cloud point system was much higher than in the control, suggesting that the cloud point system may be applied as a novel extractive bioreactor for the enzymatic hydrolysis of Pen G. Copyright © 2006 Society of Chemical Industry

Biotransformation of phytosterol to produce androsta-diene-dione by resting cells of Mycobacterium in cloud point system

A resting cell biotransformation of phytosterol to androsta-diene-dione (ADD) in cloud point system was carried out. Through optimizations of the resting cell biotransformation conditions, the benefits of biotransformation of hydrophobic compounds in cloud point system were achieved and the ADD concentration reached up to 12,000 mg/l. The advantages of biotransformation using resting cells versus using growing cells, are as follows. The cells can be repeatedly utilized. High cell concentration can be used. Biotransformation can be run under non-sterile condition. Those properties advocate that the protocol can be utilized in large-scale production.

Cloud point system as a tool to improve the efficiency of biotransformation

When an aqueous nonionic surfactant micelle solution is at a temperature above its cloud point (CP) or in presence of certain additives, phase separation occurs to from a surfactant diluted phase and a coacervate phase. This system is known as cloud point system. The paper focused on a cloud point system consisting of nonionic surfactant Triton X-100 and Triton X-114, which used as a novel two-phase partitioning bioreactor for biotransformation. The biocompatibility of Mycobacterium sp. cells in the system was investigated and a biotransformation of cholesterol into androsta-1, 4-diene-3, 17-dione (ADD) and androst-4-ene-3, 17-dione (AD) by resting cells in this system was carried out. The cells catalyze the biotransformation and further degradation of products. By determination of the substrate concentration, surfactant concentration and cell concentration on the specific ADD accumulation activity, the cloud point system can be used as a tool to improve the efficiency of biotransformation. It extracted products from cells to the coacervate phase, which could protect the product from degradation and eliminate product inhibition on the microorganism. By controlling delivery, the uneven partition of substrate in the two-phase system made the substrate concentration in the dilute phase to maintain a moderate level, which improved the mass transfer of substrate and eliminate substrate inhibition on the microorganism.

Microbial transformation of hydrophobic compound in cloud point system

Microbial transformations of hydrophobic compounds are often constrained by practical difficulties, such as substrate solubility and product inhibition. A novel approach, microbial transformation in cloud point system (CPS), was developed. The system could provide microbial cells with aqueous environment and could dissolve substrate and products in surfactant phase. A microbial transformation of cholesterol to androst-1,4-diene-3,17-dione (ADD) and androst-4-ene-3,17-dione (4-AD) has been carried out in the system consisting of nonionic surfactants Triton X-100 and Triton X-114, which is more effective than the microbial transformation in conventional media. The biocompatibility and bioavailability in the cloud point system were investigated by determination of solubilization of surfactant phase and observation of dilute phase and coacervate phase under microscopy. The system parameters of microbial transformation were optimized. It indicated that CPS has the potential capability to be utilized as an effective microbial transformation medium.

Model of bioconversion of cholesterol in cloud point system

Bioconversion of cholesterol to androst-1,4-diene-3,17-dione (ADD) and androst-4-ene-3,17-dione (4-AD) in cloud point system (CPS) was studied. A mathematical model was presented based on the mass transfer rate and microbial growth rate. The calculations for cell concentration, substrate concentration, and product concentration as functions of time were made. Sensitive analysis of model was made. Some parameters, such as substrate concentration, mass transfer coefficient, and maximum product inhibition concentration, indicated that the maximum product concentration is the most significant parameter in batch process. The prediction was validated by adjusting substrate concentration, stirring speed, and surfactant concentration. It showed the batch process of cholesterol bioconversion in CPS was controlled by inhibition of product. Adjusting surfactant concentration can diminish inhibition of product and increase final product concentration. The results also indicated that CPS can increase the substrate concentration of aqueous phase in batch process.

Cloud-point extraction and preconcentration of cyanobacterial toxins (microcystins) from natural waters using a cationic surfactant.

A new cloud-point extraction and preconcentration method using a cationic surfactant, Aliquat-336 (tricaprylylmethylammonium chloride), has been developed for the determination of cyanobacterial toxins, microcystins, in natural waters. Sodium sulfate was used to induce phase separation at 25 degrees C. The phase behavior of Aliquat-336 with respect to concentration of Na2SO4 was studied. The cloud-point system revealed a very high phase volume ratio compared to other established systems of nonionic, anionic, and cationic surfactants. At pH 6-7, it showed an outstanding selectivity in analyte extraction for anionic species. Only MC-LR and MC-YR, which are known to be predominantly anionic, were extracted (with averaged recoveries of 113.9 +/- 9% and 87.1 +/- 7%, respectively). MC-RR, which is likely to be amphoteric at the above pH range, was not detectable in the extract. Coupled to HPLC/UV separation and detection, the cloud-point extraction method (with 2.5 mM Aliquat-336 and 75 mM Na2SO4 at 25 degrees C) offered detection limits of 150 +/- 7 and 470 +/- 72 pg/mL for MC-LR and MC-YR, respectively, in 25 mL of deionized water. Repeatability of the method was 7.6% for MC-LR and 7.3% for MC-YR. The cloud-point extraction process can be completed within 10-15 min with no cleanup steps required. Applicability of the new method to the determination of microcystins in real samples was demonstrated using natural surface waters collected from a local river and a local duck pond spiked with realistic concentrations of microcystins. Effects of salinity and organic matter (TOC) content in the water sample on the extraction efficiency were also studied.

Noncritical Behavior Near the Cloud Point in Perfluorinated Ionic Micellar Solutions

The solution properties of a noncritical cloud point system, namely, sodium perfluorooctanoate/H[sub 2]O/tetrapropylammonium bromide, were investigated by dynamic and static light scattering. Critical-type behavior is observed when the temperature approaches the minimum cloud point (T[sub d]) from the one-phase region: However, for other sodium perfluorooctanoate solutions, but of lower concentration than that corresponding to the minimum cloud-point temperature, the apparent hydrodynamic radius may decrease as the temperature approaches the cloud point. It is thus shown that a cloud-point system may not always exhibit critical-type behavior as many authors believe in the literature. 30 refs., 6 figs.