Solubility in Ionic Liquids

Increasing Sugar Solubility in Ionic Liquids

• 03. 2010 – 02. 2011, Supported by the Ministry of Knowledge Economy, Korea through the Cleaner Production Technology Development Project.

Room-temperature ionic liquids (ILs) are a class of organic salts with low melting point. ILs have been spotlighted as “green solvents” due to their non-volatile characters, no measurable vapor pressure, and negligible flammability. For these reasons, ILs have been widely used as a potential replacement for traditional organic solvents in bio-industry, such as enzyme engineering. However, even though ILs are known to enhance the activity and selectivity of many enzymes, most ILs have low solubility of the hydrophilic substrate including glucose, sucrose, which can be used as enzyme substrates for the commercial products in the food industry.

In order to overcome the solubility limit of sugar molecule in ILs (i.e. glucose and sucrose), my previous research group of Inha University in South Korea developed the experimental approach, so-called water-mediate method. This method enabled to increase glucose concentration up to 10 - 19 times in ILs as compared to conventional dissolution methods in ILs. However, the mechanism responsible for the increased solubility using water-mediated method was not clear and remained to be understood. When I had worked at North Carolina State University as a visiting scholar for a year (2010 – 2011), I used computational modeling techniques to shed a light on the underlying mechanisms. My simulation results demonstrated that the water molecules act as a solubility enhancer which disrupts glucose – glucose interactions and enhances glucose – solvent (water and anion) interaction, resulting in higher glucose solubility. Also, I found that hydrogen bonding network between glucose, water, and anion in ILs molecules is a key driving force in the dissolution process of glucose in water-mediated ILs. I strongly believe that the observations from this simulation can be used as a guide in designing ILs with high solubility of sugars, therefore can be of help in maximizing productions of food additives using sugar as substrates. Furthermore, this research became a foundation of designing my further research regarding CALB enzyme in Research Field 2. For this work, I have published one journal paper in 2012 (see [1] in Journal Paper below).

Journal Paper

[1] Ho Shin Kim, Rakhee Pani, Sung Ho Ha, Yoon-Mo Koo, and Yaroslava G. Yingling. "The role of hydrogen bonding in water-mediated glucose solubility in ionic liquids." Journal of Molecular Liquids 166 (2012): 25-30