Wen Teoh | University Of Malaya (original) (raw)

Papers by Wen Teoh

Research paper thumbnail of Recent Advances in Application of Inorganic Salt Pretreatment for Transforming Lignocellulosic Biomass into Reducing Sugars

Journal of Agricultural and Food Chemistry, 2015

Currently, the transformation of lignocellulosic biomass into value-added products such as reduci... more Currently, the transformation of lignocellulosic biomass into value-added products such as reducing sugars is garnering attention worldwide. However, efficient hydrolysis is usually hindered by the recalcitrant structure of the biomass. Many pretreatment technologies have been developed to overcome the recalcitrance of lignocellulose such that the components can be reutilized more effectively to enhance sugar recovery. Among all of the utilized pretreatment methods, inorganic salt pretreatment represents a more novel method and offers comparable sugar recovery with a potential for reducing costs. The use of inorganic salt also shows improved performance when it is integrated with other pretreatment technologies. Hence, this review is aimed to provide a detailed overview of the current situation for lignocellulosic biomass and its physicochemical characteristics. Furthermore, this review discusses some recent studies using inorganic salt for pretreating biomass and the mechanisms involved during the process. Finally, some prospects and challenges using inorganic salt are highlighted in this review.

Research paper thumbnail of Micronization and encapsulation of 5-fluorouracil using dense gas technology

Supercritical fluid processing has been shown to be successful in the micronization and encapsula... more Supercritical fluid processing has been shown to be successful in the micronization and encapsulation of several pharmaceutical compounds, overcoming limitations associated with conventional techniques. Of recent interest is the controlled-release drug delivery of 5-fluorouracil (5FU) for the treatment of cancer. Polymeric materials such as poly-(L-lactic acid) (PLLA) and Eudragit® RS100 have been found to be promising drug carriers, as they are biocompatible, and provide a greater level of controlled release, as the pharmaceutical compound is released in vivo via diffusion through the polymer matrix. 5-Fluorouracil (5FU) belongs to the class of pyrimidine analogs and is the most effective found to treat advanced colorectal cancer, being used as the first line of treatment for decades (Longley et al., 2003). It has also been used to treat stomach, breast, head and neck cancers. While current commercial formulations of 5FU are mostly intravenous and topical formulations, oral formula...

Research paper thumbnail of Saturation Pressure Estimation of Low Volatile Organic Compounds in Supercritical Fluids

Research paper thumbnail of Ternary Solubilities of Anthracene in Pressurized Binary Water/Ethanol Mixtures at Temperatures Ranging From 393 K to 473 K

Solubility measurements were conducted for (1-x) water – x ethanol mixtures at mole fractions, x ... more Solubility measurements were conducted for (1-x) water – x ethanol mixtures at mole fractions, x = 0, 0.02, 0.03 and 0.04 of ethanol in pressurized water/ethanol system at 50 bar between 393 K and 473 K. A static equilibrium method was utilized to measure the solubilities of anthracene. Experimental data shows that the addition of a small amount of a volatile co-solvent to an aqueus mixture enhances the solubility of a hydrophobic compound. It was found that the addition of ethanol is much more effective in enhancing the solubility of anthracene at the higher temperatures. At every concentration of ethanol studied, a plot of the log of solubility of anthracene versus temperature yields a near linear plot. Thermodynamic functions of transfer from water to water/ethanol mixtures were also derived from solubility data. The free energy of transfer for anthracene was found to decrease with the increase of x; validating that anthracene is less hydrophobic as the concentration of ethanol i...

Research paper thumbnail of Particle Engineering by Dense Gas Technologies Applied to Pharmaceuticals

Food and Pharmaceutical Applications, 2012

Research paper thumbnail of Solubility prediction of low volatile solutes in supercritical carbon dioxide in the absence of saturation pressure data

The Journal of Supercritical Fluids, 2007

Saturation pressure parameter is one of the most important properties in thermodynamic studies. B... more Saturation pressure parameter is one of the most important properties in thermodynamic studies. Besides experimental measurements, many correlations and equations have been developed to determine saturation pressure for range of components. However, most of them require critical properties of the components, which are unavailable for most of heavy and low volatile components. In this paper, a technique was suggested to estimate the saturation pressure of low volatile components dissolved in supercritical carbon dioxide. The Dilute Solution Theory (DST) model was applied to two compound groups, namely the arenes (aromatic compounds) and the vegetable oils, by fitting two common adjustable parameters for each group. The saturation pressure for each compound was calculated using a newly developed equation. It was found that the estimated saturation pressures at each temperature studied were in good agreement with the values calculated by Antoine equation or by data extrapolation from literature.

Research paper thumbnail of Dense Phase Carbon Dioxide: Food and Pharmaceutical Applications

ABSTRACT The application of dense phase carbon dioxide for the pasteurization of liquid foods has... more ABSTRACT The application of dense phase carbon dioxide for the pasteurization of liquid foods has fostered research in the study of the phase behavior of systems in which CO2 is in contact with liquid foods of different compositions in different processing conditions of pressure and temperature. CO2 solubility in liquid phase is the key parameter for proper design of these processes. In this chapter, a review of the systems designed to experimentally measure CO2 solubility and the resulting experimental data are reported starting from the results of CO2 solubility in water and continuing with more complex aqueous solutions.

Research paper thumbnail of Solubility of organometallic complexes in supercritical carbon dioxide: a review

The solubility of organometallic complexes and their solubility trends in supercritical carbon di... more The solubility of organometallic complexes and their solubility trends in supercritical carbon dioxide were reviewed. A number of thermodynamic models currently used to predict the solute-fluid behavior of organometallic complexes in supercritical carbon dioxide, and the advantages and limitations to these thermodynamic models, were also discussed.

Research paper thumbnail of Solubility and Solubility Modelling of Polycyclic Aromatic Hydrocarbons in Subcritical Ethanol and Water Mixtures

The solubility of anthracene and p-terphenyl in subcritical ethanol and water mixtures were measu... more The solubility of anthracene and p-terphenyl in subcritical ethanol and water mixtures were measured using a static analytical equilibrium method between 393 and 473 K, and at 50 and 150 bar. Temperature and ethanol composition in the subcritical solvent mixtures were found to have significant effects on the solubility of polycyclic aromatic hydrocarbons (PAHs). The effect of pressure on solubility is negligible when the range of pressure considered is relatively small. An empirical model was proposed in the present study to correlate the solubility of PAHs to temperature and ethanol mole fraction. UNIQUAC, O-UNIFAC and M-UNIFAC models were compared, with the UNIQUAC model found to be in good agreement with experimental data.

Research paper thumbnail of Solubility and solubility modelling of polycyclic aromatic hydrocarbons in subcritical water

A static analytical equilibrium method was used to measure the binary and ternary solubilities of... more A static analytical equilibrium method was used to measure the binary and ternary solubilities of anthracene and p-terphenyl in subcritical water between 393 K and 473 K, and at 50 bar and 150 bar. Temperature was found to have the most significant effect on the solubility of polycyclic aromatic hydrocarbons (PAHs) in subcritical water. The effect of pressure, and the combined effect of temperature and pressure on solubility were found to be insignificant, particularly when the range of pressure considered is relatively small. The solubilities of PAHs were found to be governed primarily by sublimation pressure, and only secondarily by the dielectric constant of water. The Peng-Robinson equation of state was used to correlate the aqueous solubilities of PAHs at subcritical conditions, with good agreement between experimental and calculated values obtained for binary systems. HIGHLIGHTS  Solubilities of PAHs in subcritical water increased exponentially with temperature.  Temperature and solutes sublimation pressure govern solid solute solubility.  The effect of the dielectric constant on solubility is secondary.  The effects of pressure and density on solubility are insignificant.  Peng-Robinson equation of state provides good correlation with experimental data.

Research paper thumbnail of Recent Advances in Application of Inorganic Salt Pretreatment for Transforming Lignocellulosic Biomass into Reducing Sugars

Journal of Agricultural and Food Chemistry, 2015

Currently, the transformation of lignocellulosic biomass into value-added products such as reduci... more Currently, the transformation of lignocellulosic biomass into value-added products such as reducing sugars is garnering attention worldwide. However, efficient hydrolysis is usually hindered by the recalcitrant structure of the biomass. Many pretreatment technologies have been developed to overcome the recalcitrance of lignocellulose such that the components can be reutilized more effectively to enhance sugar recovery. Among all of the utilized pretreatment methods, inorganic salt pretreatment represents a more novel method and offers comparable sugar recovery with a potential for reducing costs. The use of inorganic salt also shows improved performance when it is integrated with other pretreatment technologies. Hence, this review is aimed to provide a detailed overview of the current situation for lignocellulosic biomass and its physicochemical characteristics. Furthermore, this review discusses some recent studies using inorganic salt for pretreating biomass and the mechanisms involved during the process. Finally, some prospects and challenges using inorganic salt are highlighted in this review.

Research paper thumbnail of Micronization and encapsulation of 5-fluorouracil using dense gas technology

Supercritical fluid processing has been shown to be successful in the micronization and encapsula... more Supercritical fluid processing has been shown to be successful in the micronization and encapsulation of several pharmaceutical compounds, overcoming limitations associated with conventional techniques. Of recent interest is the controlled-release drug delivery of 5-fluorouracil (5FU) for the treatment of cancer. Polymeric materials such as poly-(L-lactic acid) (PLLA) and Eudragit® RS100 have been found to be promising drug carriers, as they are biocompatible, and provide a greater level of controlled release, as the pharmaceutical compound is released in vivo via diffusion through the polymer matrix. 5-Fluorouracil (5FU) belongs to the class of pyrimidine analogs and is the most effective found to treat advanced colorectal cancer, being used as the first line of treatment for decades (Longley et al., 2003). It has also been used to treat stomach, breast, head and neck cancers. While current commercial formulations of 5FU are mostly intravenous and topical formulations, oral formula...

Research paper thumbnail of Saturation Pressure Estimation of Low Volatile Organic Compounds in Supercritical Fluids

Research paper thumbnail of Ternary Solubilities of Anthracene in Pressurized Binary Water/Ethanol Mixtures at Temperatures Ranging From 393 K to 473 K

Solubility measurements were conducted for (1-x) water – x ethanol mixtures at mole fractions, x ... more Solubility measurements were conducted for (1-x) water – x ethanol mixtures at mole fractions, x = 0, 0.02, 0.03 and 0.04 of ethanol in pressurized water/ethanol system at 50 bar between 393 K and 473 K. A static equilibrium method was utilized to measure the solubilities of anthracene. Experimental data shows that the addition of a small amount of a volatile co-solvent to an aqueus mixture enhances the solubility of a hydrophobic compound. It was found that the addition of ethanol is much more effective in enhancing the solubility of anthracene at the higher temperatures. At every concentration of ethanol studied, a plot of the log of solubility of anthracene versus temperature yields a near linear plot. Thermodynamic functions of transfer from water to water/ethanol mixtures were also derived from solubility data. The free energy of transfer for anthracene was found to decrease with the increase of x; validating that anthracene is less hydrophobic as the concentration of ethanol i...

Research paper thumbnail of Particle Engineering by Dense Gas Technologies Applied to Pharmaceuticals

Food and Pharmaceutical Applications, 2012

Research paper thumbnail of Solubility prediction of low volatile solutes in supercritical carbon dioxide in the absence of saturation pressure data

The Journal of Supercritical Fluids, 2007

Saturation pressure parameter is one of the most important properties in thermodynamic studies. B... more Saturation pressure parameter is one of the most important properties in thermodynamic studies. Besides experimental measurements, many correlations and equations have been developed to determine saturation pressure for range of components. However, most of them require critical properties of the components, which are unavailable for most of heavy and low volatile components. In this paper, a technique was suggested to estimate the saturation pressure of low volatile components dissolved in supercritical carbon dioxide. The Dilute Solution Theory (DST) model was applied to two compound groups, namely the arenes (aromatic compounds) and the vegetable oils, by fitting two common adjustable parameters for each group. The saturation pressure for each compound was calculated using a newly developed equation. It was found that the estimated saturation pressures at each temperature studied were in good agreement with the values calculated by Antoine equation or by data extrapolation from literature.

Research paper thumbnail of Dense Phase Carbon Dioxide: Food and Pharmaceutical Applications

ABSTRACT The application of dense phase carbon dioxide for the pasteurization of liquid foods has... more ABSTRACT The application of dense phase carbon dioxide for the pasteurization of liquid foods has fostered research in the study of the phase behavior of systems in which CO2 is in contact with liquid foods of different compositions in different processing conditions of pressure and temperature. CO2 solubility in liquid phase is the key parameter for proper design of these processes. In this chapter, a review of the systems designed to experimentally measure CO2 solubility and the resulting experimental data are reported starting from the results of CO2 solubility in water and continuing with more complex aqueous solutions.

Research paper thumbnail of Solubility of organometallic complexes in supercritical carbon dioxide: a review

The solubility of organometallic complexes and their solubility trends in supercritical carbon di... more The solubility of organometallic complexes and their solubility trends in supercritical carbon dioxide were reviewed. A number of thermodynamic models currently used to predict the solute-fluid behavior of organometallic complexes in supercritical carbon dioxide, and the advantages and limitations to these thermodynamic models, were also discussed.

Research paper thumbnail of Solubility and Solubility Modelling of Polycyclic Aromatic Hydrocarbons in Subcritical Ethanol and Water Mixtures

The solubility of anthracene and p-terphenyl in subcritical ethanol and water mixtures were measu... more The solubility of anthracene and p-terphenyl in subcritical ethanol and water mixtures were measured using a static analytical equilibrium method between 393 and 473 K, and at 50 and 150 bar. Temperature and ethanol composition in the subcritical solvent mixtures were found to have significant effects on the solubility of polycyclic aromatic hydrocarbons (PAHs). The effect of pressure on solubility is negligible when the range of pressure considered is relatively small. An empirical model was proposed in the present study to correlate the solubility of PAHs to temperature and ethanol mole fraction. UNIQUAC, O-UNIFAC and M-UNIFAC models were compared, with the UNIQUAC model found to be in good agreement with experimental data.

Research paper thumbnail of Solubility and solubility modelling of polycyclic aromatic hydrocarbons in subcritical water

A static analytical equilibrium method was used to measure the binary and ternary solubilities of... more A static analytical equilibrium method was used to measure the binary and ternary solubilities of anthracene and p-terphenyl in subcritical water between 393 K and 473 K, and at 50 bar and 150 bar. Temperature was found to have the most significant effect on the solubility of polycyclic aromatic hydrocarbons (PAHs) in subcritical water. The effect of pressure, and the combined effect of temperature and pressure on solubility were found to be insignificant, particularly when the range of pressure considered is relatively small. The solubilities of PAHs were found to be governed primarily by sublimation pressure, and only secondarily by the dielectric constant of water. The Peng-Robinson equation of state was used to correlate the aqueous solubilities of PAHs at subcritical conditions, with good agreement between experimental and calculated values obtained for binary systems. HIGHLIGHTS  Solubilities of PAHs in subcritical water increased exponentially with temperature.  Temperature and solutes sublimation pressure govern solid solute solubility.  The effect of the dielectric constant on solubility is secondary.  The effects of pressure and density on solubility are insignificant.  Peng-Robinson equation of state provides good correlation with experimental data.