ORIGINAL PAPER An Efficient Binary Solvent Mixture for Monoacylglycerol Synthesis by Enzymatic Glycerolysis Nanjing Zhong Æ Lin Li Æ Xuebing Xu Æ Lingzhi Cheong Æ Bing Li Æ Songqing Hu Æ Xihong Zhao Received: 18 January 2009 / Revised: 5 May 2009 / Accepted: 17 May 2009 / Published online: 7 June 2009 Ó AOCS 2009 Abstract The present study was aimed at selecting an efficient binary solvent mixture for monoacylglycerol (MAG) synthesis by enzymatic glycerolysis of soybean oil. Solvent combinations of tert-butanol/isopropanol (v/v) at different ratios were studied. Of the investigated cases, tert-butanol:isopropanol at ratio 80:20 was the most suit- able organic medium. The optimum conditions for MAG synthesis under the selected mixture were: water 10 wt% based on glycerol, Lipozyme TL IM 15 wt% based on oil and glycerol, weight ratio of solvent to oil 4:1, and molar ratio of glycerol to oil 3.5:1. Under these conditions with a 4-h reaction, the yield of MAG was 72.0% where the tri- acylglycerol (TAG) content was reduced to only 1.0% (based on acylglycerols). Fatty acid ester (FAE) formation from the solvents was very low in the final product (1.3% based on reaction mixture). The selected binary solvent mixture has good physical properties with low melting point (-26.5 °C), which can avoid the risk of crystalliza- tion in practical operations. Keywords Glycerolysis  Monoacylglycerol  Lipozyme TL IM  Binary solvent medium  Soybean oil Introduction Monoacylglycerols (MAG) are recognized as safe food- grade additives by the American Food and Drug Admin- istration and the EU. MAG, or their mixtures with diacylglycerols (DAG), account for approximately 75% of worldwide emulsifier production, which has been estimated at about 200,000–250,000 metric tons per year. MAG are widely used as emulsifiers in the food, pharmaceutical and cosmetic industries. They are also used as synthetic inter- mediates and as chiral building blocks in synthetic organic chemistry [1–5]. Conventionally, commercial MAG are widely manu- factured by chemical glycerolysis of oils and fats at high temperatures of 200–250 °C, using inorganic alkaline such as NaOH or Ca(OH) 2 as catalysts [3, 4, 6]. The process presents some drawbacks such as dark color, burnt taste, and high energy consumption. In particular, it is not suit- able for heat-sensitive MAG production [1, 3, 4]. MAG can be produced through direct esterification of glycerol with fatty acids (FA). Macrae et al. [7] reported a reaction product containing [ 95 mol% MAG by using potato lipid acyl hydrolase to synthesize MAG from glycerol and FA. Since then, the use of enzymes as catalysts has received considerable attention for several years because of the much lower temperature required [2–6, 8]. However, at low temperatures, glycerol and the oil are immiscible, hence enzymatic glycerolysis of tricaylglyce- rols (TAG) typically yields only 30–50% of MAG [3, 5]. To enhance the reaction efficiency, various strategies have been reported [9–11]. A two-step temperature program- ming method was found to be helpful for higher MAG yield in which the reaction mixture was first incubated at 42 °C for 8–16 h followed by reducing the reaction tem- perature to 5 °C for up to 4 days. The protocol is limited as N. Zhong  L. Li  B. Li (&)  S. Hu  X. Zhao College of Light Industry and Food Sciences, South China University of Technology, 510640 Guangzhou, People’s Republic of China e-mail: lcbingli@scut.edu.cn N. Zhong e-mail: adong473@163.com X. Xu  L. Cheong Department of Molecular Biology, Aarhus University, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark 123 J Am Oil Chem Soc (2009) 86:783–789 DOI 10.1007/s11746-009-1402-7