Notes Bull. Korean Chem. Soc. 2010, Vol. 31, No. 2 511 DOI 10.5012/bkcs.2010.31.02.511 Acidity Tunable Ionic Liquids as Catalysts for Conversion of Agar into Mixed Sugars Churl Kim, † Hyun Jin Ryu, Sang Hyoun Kim, Jeong-Jun Yoon, Hoon Sik Kim, †,* and Yong Jin Kim * Green Process R&D Department, Green Chemistry and Manufacturing System Division, Korea Institute of Industrial Technology, Cheonan, Chungnam 331-825, Korea. * E-mail: yjkim@kitech.re.kr † Department of Chemistry and Research Institute of Basic Science, Kyung Hee University, Seoul 130-701, Korea Received December 14, 2009, Accepted January 5, 2010 Key Words: Ionic liquid, Saccharification, Red algae, Galactose, 5-Hydroxymethylfurfural As oil prices spike to a new level, the importance of alter- native resources and fuels becoming more apparent and the use of bioethanol as an alternative steadily increases around the world. 1,2 Accordingly, there have been significantly increas- ing endeavors on the technology development that facilitate the transformation of biorenewables into transportation fuels. To meet this end, many technologies have employed sugar- and corn-based biomass for the industrial production of bioethanol, especially in Brazil and U. S., respectively. While they contri- buted a lot to the commercialization process, the viability of the so-called 1 st generation biofuels is somewhat questionable because of their conflict with food supply. Another key factor influencing biofuel efficacy is whether native ecosystems can be maintained or not. No matter how effective biomass is for producing ethanol, its benefits quickly decrease if all the tropical forests are being razed to make energy crops, leading to another type of a large amount of greenhouse gas (GHG) emission path- way. 3 To solve this crisis, a new type of biomass should be developed and their biofuels should be produced locally in sus- tainable systems. From this viewpoint, seaweeds (macro algae) can be an excellent alternative raw material as a new marine biomass for biofuel production. Among them, Gelidium amansii is one most abundantly available red seaweed (Rodophyta) spe- cies along the shallow coastal area of many countries. It mainly consists of polysaccharide complexes of fiber and agar whose basic monomer is glucose and galactose residue, respectively. Generally, there are five major bottom lines for a bioethanol process to be economically viable: the feedstock must be plenti- ful, inexpensive, in high energy conversion rate, in low demand for food industry, and finally, has to be cultivated in sustainable systems. Accordingly, red seaweed shows very fast growing rate (4 - 6 harvest cycles per year) with high CO2 fixation ability which is 5 - 7 times higher than that of a land plant. Furthermore, they can be mass-cultivated using sea water and free sunlight without any need of nitrogen-based fertilizer which has been a significant source of GHG that also destroys stratospheric ozone. 4 Red seaweed shows very high carbohydrate content up to 75% (w/w) based on dried sample and does not cause food supply problems at all. In addition, they do not contain any lignin that has to be eliminated prior to hydrolysis step, which has been a major obstacle to increase production cost in ligno- cellulosic process. Furthermore, the red seaweed has an ability to absorb nitrogen and phosphorous thereby purifying sea water which leads to oceans’ sustainability. Recently, an effort has been made for the utilization of the fiber extracted from Gelidium amansii, to the making of high quality pulp & paper. 5 Therefore, the agar will be an inevitable byproduct during the process of manufacturing red algae-based paper in future. In general, lignocellulosic bioethanol process involves a pretreatment step for delignification to remove lignin contents, which results in somewhat complicated and cost-pro- voking unit process. In contrast, the pretreatment step for obtain- ing agar from red seaweed is very simple. The agar and fiber residue can be separated from the original substrate, Gelidium amansii with boiling water. Utilization of marine biomass strate- gy therefore reduces the number of required unit process drama- tically, leading to cutting down the production cost significantly. Room temperature ionic liquids have been widely applied for task-specific purposes, especially their economical and promis- ing role as active catalysts in organic synthesis. 6 Despite many efforts that have been devoted to ionic liquids-derived chemical processes, there have been no studies on their catalytic biocon- version process using red seaweed galactan (agar) as a substrate to produce fermentable sugars. In case of agar, the 5-hydroxy- methylfurfural (5-HMF) is mainly generated from the deg- radation of 3,6-anhydrogalactose (AG) due to its acid-labile character. 7 Using a strong inorganic acid such as H2SO4 in the saccharification step accelerates the formation of 5-HMF, result- ing in pivotal hamper in terms of ethanol fermentation efficacy. Incorporation of ionic liquids with conventional inorganic acid systems may enable to reduce acidity from moderate to weak depending on their type of cation, shedding light on minimizing the generation of 5-HMF. In this context, various bisulfate-containing acidic ionic liquids as hydrolytic catalysts for the saccharification of agar extracted from Gelidium amansii have been investigated and compared with conventional sulfuric acid system from the view- point of sugar yields and 5-HMF formation. Determination of chemical composition is of great impor- tance since the yields of sugars are calculated based on the compositional analytical data. Normally, acid hydrolysis is a common procedure for determining lignocellulosic biomass, which consists of two-steps: First, hydrolysis with 72% (w/v) H2SO4 at 30 o C for 2 h, followed by the dilution into 4% of the reaction mixture and then second hydrolysis at 121 o C for 1 h. The same methodology was applied to the analysis of Glu and Gal, but 1% (w/v) H 2 SO 4 was employed for AG at the first hydrolytic step due to its easy degradation mode. The agar ex-