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Xiandeng Hou - One of the best experts on this subject based on the ideXlab platform.
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selective determination of trace amounts of silver in complicated matrices by displacement Cloud Point extraction coupled with thermospray flame furnace atomic absorption spectrometry
Journal of Analytical Atomic Spectrometry, 2008Co-Authors: Ying Gao, Guanglei Cheng, Wenshu Yang, Xiandeng HouAbstract:A novel displacement-Cloud Point extraction approach was developed for the selective determination of trace silver in complicated matrices by thermospray flame furnace atomic absorption spectrometry. This method involves two steps of Cloud Point extraction, i.e., firstly, copper ion reacts with diethyldithiocarbamate (DDTC) to form Cu-DDTC before it is extracted; secondly, after removing the aqueous phase, a sample or standard solution containing silver ion is added and another Cloud Point extraction procedure is carried out. Because the stability of Ag-DDTC is larger than that of Cu-DDTC, Ag+ can displace Cu2+ from the pre-extracted Cu-DDTC and thus the preconcentration and separation of Ag+ from complicated sample matrix is achieved. Potential interference from co-existing transition metal ions with lower DDTC complex stability was largely eliminated as they cannot displace Cu2+ from Cu-DDTC complex. Up to 5000 μg mL−1Ni(II), 2000 μg mL−1 Cd(II), 1000 μg mL−1Fe(III), 2000 μg mL−1Co(II), 5000 μg mL−1Zn(II) and 5000 μg mL−1Mn(II) caused no significant interference with the determination of silver of 5 μg L−1. Compared with conventional Cloud Point extraction, the tolerance limit for the co-existing transition metal ions was increased by at least two orders of magnitude. Under the optimal chemical and instrumental conditions, the limit of detection was 0.2 μg L−1 for silver with a sample volume of 10 mL, and a sensitivity enhancement factor of 21 was achieved. The proposed method was successfully applied to interference-free determination of trace silver in soil, marine sediment and ore samples with high contents of co-existing heavy metals.
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Cloud Point extraction thermospray flame quartz furnace atomic absorption spectrometry for determination of ultratrace cadmium in water and urine
Spectrochimica Acta Part B: Atomic Spectroscopy, 2006Co-Authors: Yunchang Zhang, Xiandeng HouAbstract:Abstract A simple, low cost and highly sensitive method based on Cloud Point extraction (CPE) for separation/preconcentration and thermospray flame quartz furnace atomic absorption spectrometry was proposed for the determination of ultratrace cadmium in water and urine samples. The analytical procedure involved the formation of analyte-entrapped surfactant micelles by mixing the analyte solution with an ammonium pyrrolidinedithiocarbamate (APDC) solution and a Triton X-114 solution. When the temperature of the system was higher than the Cloud Point of Triton X-114, the complex of cadmium-PDC entered the surfactant-rich phase and thus separation of the analyte from the matrix was achieved. Under optimal chemical and instrumental conditions, the limit of detection was 0.04 μg/L for cadmium with a sample volume of 10 mL. The analytical results of cadmium in water and urine samples agreed well with those by ICP-MS.
Hanshi Qi - One of the best experts on this subject based on the ideXlab platform.
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Extractive fermentation in Cloud Point system for lipase production by Serratia marcescens ECU1010
Applied Microbiology and Biotechnology, 2010Co-Authors: Tao Pan, Zhenqiang Wu, Jian-he Xu, Zhilong Wang, Hanshi QiAbstract:Extractive microbial fermentation for production of lipase by Serratia marcescens ECU1010 has been carried out in Cloud Point system. The Cloud Point system is composed of mixture nonionic surfactants with a ratio of Triton X-114 to Triton X-45 4:1 in aqueous solution. The lipase prefers to partition into the surfactant rich phase (coacervate phase) whereas the cells and other hydrophilic proteins retain in the dilute phase of Cloud Point system. Thus, a concentration factor 4.2-fold and a purification factor 1.3-fold of the lipase have been achieved in the extractive fermentation process. This is the first report about extractive fermentation of proteins in Cloud Point system.
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novel polyethylene glycol induced Cloud Point system for extraction and back extraction of organic compounds
Separation and Purification Technology, 2009Co-Authors: Rui Liang, Zhilong Wang, Jian-he Xu, Wei Li, Hanshi QiAbstract:Abstract A novel polyethylene glycol (PEG) induced Cloud Point system (PEG-CPS) with high hydrophile–lipophile balance (HLB) value nonionic surfactant and high molecular weight PEG had been developed for extraction of organic compounds. The main advantage of this novel system is that the back extraction process of stripping of nonvolatile organic compounds from the nonionic surfactant aqueous solution can be carried out with Winsor I microemulsion extraction. Thus a separation of organic compounds from the nonionic surfactants in aqueous solution become possible, which is potential for Cloud Point extraction (CPE) or extractive microbial transformation in Cloud Point system from economical and environmental consideration. With Triton X-100 as a model hydrophilic nonionic surfactant, the phase diagram of PEG-CPS was determined. High boiling Point organic compounds, such as phenol, p -nitrophenol and 1-naphthol phenol, were extracted with PEG-CPS. Then the organic compounds in the surfactant rich phase of PEG-CPS were back-extracted with microemulsion.
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production of l phenylacetylcarbinol by microbial transformation in polyethylene glycol induced Cloud Point system
Applied Microbiology and Biotechnology, 2008Co-Authors: Wenzhi Zhang, Zhilong Wang, Wei Li, Baohua Zhuang, Hanshi QiAbstract: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 MgSO4·7H2O, 0.05 g CaCl2·2H2O, 35 g Na2HPO4·12H2O, 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.
Zhilong Wang - One of the best experts on this subject based on the ideXlab platform.
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extractive microbial fermentation in Cloud Point system
Enzyme and Microbial Technology, 2010Co-Authors: Zhilong Wang, Zewen DaiAbstract:Extractive microbial fermentation of organic compounds in liquid-liquid two-phase systems is a potential strategy to overcome the limitations of microbial fermentation in an aqueous solution, such as low substrate solubility, substrate/product inhibition and product further degradation. A conventional aqueous-organic solvent two-phase system is inaccessible to extractive fermentation of a relatively high polar bioproduct as the confliction between the biocompatibility and the extraction ability of the corresponding organic solvent. An exploitation of Cloud Point system as a novel medium engineering method for extractive microbial fermentation is reviewed in present work. The relationship between phase separation of nonionic surfactant aqueous solution forming Cloud Point system and its corresponding biocompatibility to microorganisms, and the relationship between solubilization and bioavailability of organic compounds in a Cloud Point system are discussed. Paradigms of extractive microbial fermentation in Cloud Point system are highlighted with some cases in our lab. The downstream processing for nonionic surfactant recovery and product separation with microemulsion extraction is also presented.
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Extractive fermentation in Cloud Point system for lipase production by Serratia marcescens ECU1010
Applied Microbiology and Biotechnology, 2010Co-Authors: Tao Pan, Zhenqiang Wu, Jian-he Xu, Zhilong Wang, Hanshi QiAbstract:Extractive microbial fermentation for production of lipase by Serratia marcescens ECU1010 has been carried out in Cloud Point system. The Cloud Point system is composed of mixture nonionic surfactants with a ratio of Triton X-114 to Triton X-45 4:1 in aqueous solution. The lipase prefers to partition into the surfactant rich phase (coacervate phase) whereas the cells and other hydrophilic proteins retain in the dilute phase of Cloud Point system. Thus, a concentration factor 4.2-fold and a purification factor 1.3-fold of the lipase have been achieved in the extractive fermentation process. This is the first report about extractive fermentation of proteins in Cloud Point system.
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novel polyethylene glycol induced Cloud Point system for extraction and back extraction of organic compounds
Separation and Purification Technology, 2009Co-Authors: Rui Liang, Zhilong Wang, Jian-he Xu, Wei Li, Hanshi QiAbstract:Abstract A novel polyethylene glycol (PEG) induced Cloud Point system (PEG-CPS) with high hydrophile–lipophile balance (HLB) value nonionic surfactant and high molecular weight PEG had been developed for extraction of organic compounds. The main advantage of this novel system is that the back extraction process of stripping of nonvolatile organic compounds from the nonionic surfactant aqueous solution can be carried out with Winsor I microemulsion extraction. Thus a separation of organic compounds from the nonionic surfactants in aqueous solution become possible, which is potential for Cloud Point extraction (CPE) or extractive microbial transformation in Cloud Point system from economical and environmental consideration. With Triton X-100 as a model hydrophilic nonionic surfactant, the phase diagram of PEG-CPS was determined. High boiling Point organic compounds, such as phenol, p -nitrophenol and 1-naphthol phenol, were extracted with PEG-CPS. Then the organic compounds in the surfactant rich phase of PEG-CPS were back-extracted with microemulsion.
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production of l phenylacetylcarbinol by microbial transformation in polyethylene glycol induced Cloud Point system
Applied Microbiology and Biotechnology, 2008Co-Authors: Wenzhi Zhang, Zhilong Wang, Wei Li, Baohua Zhuang, Hanshi QiAbstract: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 MgSO4·7H2O, 0.05 g CaCl2·2H2O, 35 g Na2HPO4·12H2O, 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.
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improvement the tolerance of baker s yeast to toxic substrate product with Cloud Point system during the whole cell microbial transformation
Enzyme and Microbial Technology, 2007Co-Authors: Zhilong Wang, Wenzhi Zhang, Li Wang, Baohua ZhuangAbstract:Abstract 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.
Malcolm A Kelland - One of the best experts on this subject based on the ideXlab platform.
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does the Cloud Point temperature of a polymer correlate with its kinetic hydrate inhibitor performance
Energy & Fuels, 2019Co-Authors: Erik Gisle Dirdal, Malcolm A KellandAbstract:Most polymers used in commercial kinetic hydrate inhibitor (KHI) formulations show thermoresponsive behavior in aqueous solution. This means that they exhibit a Cloud Point (or lower critical solution temperature) which is often low and not far above the equilibrium temperature for gas hydrate formation. For example, poly(N-vinyl caprolactam) has a Cloud Point of about 30–40 °C and poly(N-isopropylmethacrylamide) has a Cloud Point of about 35–45 °C depending on the molecular weight and method of polymerization. This report is divided into two parts. First, we review previous KHI studies and show that low Cloud Point is a useful factor, but not the most critical factor, to be considered within a specific class of polymers in designing a high-performance KHI. This statement is supported in the second part of this report, which is an experimental KHI study. In this study, we present results of KHI tests for a natural gas/deionized water structure II gas hydrate-forming system using low Cloud Point polymers w...
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Does the Cloud Point Temperature of a Polymer Correlate with Its Kinetic Hydrate Inhibitor Performance
Energy & Fuels, 2019Co-Authors: Erik Gisle Dirdal, Malcolm A KellandAbstract:Most polymers used in commercial kinetic hydrate inhibitor (KHI) formulations show thermoresponsive behavior in aqueous solution. This means that they exhibit a Cloud Point (or lower critical solut...
Wenzhi Zhang - One of the best experts on this subject based on the ideXlab platform.
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production of l phenylacetylcarbinol by microbial transformation in polyethylene glycol induced Cloud Point system
Applied Microbiology and Biotechnology, 2008Co-Authors: Wenzhi Zhang, Zhilong Wang, Wei Li, Baohua Zhuang, Hanshi QiAbstract: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 MgSO4·7H2O, 0.05 g CaCl2·2H2O, 35 g Na2HPO4·12H2O, 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.
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improvement the tolerance of baker s yeast to toxic substrate product with Cloud Point system during the whole cell microbial transformation
Enzyme and Microbial Technology, 2007Co-Authors: Zhilong Wang, Wenzhi Zhang, Li Wang, Baohua ZhuangAbstract:Abstract 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.