Lipase‐Catalyzed Synthesis of Saccharide–Fatty Acid Esters Using Suspensions of Saccharide Crystals in Solvent‐Free Media

Abstract

Saccharide-fatty acid esters, important biobased and biodegradable emulsifiers in foods, cosmetics, and pharmaceuticals, were produced with high yields and productivity via immobilized Rhizomucor miehei lipasecatalyzed esterification in solvent-free systems at 65°C. Preliminary experiments demonstrated high rates of reaction occurred in the presence of acetone near or above its boiling point, due to the formation of 10-200 lm suspensions of saccharide particles. Subsequently, a two-step process was developed to produce a solvent-free supersaturated solution of 1.5-2.0 wt% saccharide that remained stable for C10-12 h. The solvent-free suspensions were used in a bioreactor system at 65°C, consisting of a reservoir open to the atmosphere that contained molecular sieves, a peristaltic pump, and a packed bed bioreactor, operated under continuous recirculation. At 10 h intervals, suspensions were re-formed by treating the substrate/ product mixture with additional acyl acceptor and applying strong agitation. Using this system and approach, a product mixture containing 88% fructose oleate was formed, of which 92% was monoester, within 6 days. This equates to a productivity of 0.2 mmol h -1 g -1 , which is similar to values reported for synthesis in the presence of solvent.

Solvent-Free Lipase-Catalyzed Synthesis of Technical-Grade Sugar Esters and Evaluation of Their Physicochemical and Bioactive Properties

“…The productivity for ester production for the reactions depicted in Figure 1A-D were 0.035 mmol¨h´1¨g lipase´1 and 0.025 mmol¨h´1¨g lipase´1 for fructose and sucrose oleate, respectively. The former productivity is one order of magnitude higher than that obtained during the final stage of reaction (~82% to~88% ester) in our previous publications, 0.0014-0.0017 mmol¨h´1¨g lipase´1 [15,16], and comparable to the productivity of lipase-catalyzed synthesis of sucrose palmitate in the presence of a 2-methyl-2-butanol/dimethylsulfoxide mixture [23]. The presence of CaSO 4 reduced the water concentration from 0.49% to 0.09% for fructose oleate and from 0.51% to 0.12% for sucrose oleate ( Figure 1B).…”

“…Deionized water was used throughout and all materials were used without further purification. Crude grades of sugar esters-sucrose oleate, consisting of 80.5 wt % ester (of which 92.5% is monoester and 7.5% diester), and 19.5 wt % oleic acid, and sucrose oleate, containing 83.4 wt % ester (91.2% monoester, 8.8% diester) and 16.6 wt % oleic acid-were synthesized under solvent-free conditions, using a bioreactor system, operated under continuous recirculation, with a PBBR containing RML [15]. Microorganisms and the Ehrlich ascites tumor cell line were purchased from American Type Culture Collection (Manassas, VA, USA).…”

“…Prior to measure the saccharide content using HPLC, 40 mg-sized aliquots of reaction mixture were mixed with n-hexane and water (500 µL of each), based on our pervious method [15] at 35˝C for 2 h using a thermomixer (model 022670158, Eppendorf AG, Hamburg, Germany). An analytical Prevail Carbohydrate ES column (4.6 mmˆ250 mm, pore diameter 5 µm) from Grace was used to measure the saccharide content at 25˝C with an isocratic solvent system containing acetonitrile/deionized water (80/20 v/v) at flow rate of 1 mL¨min´1.…”

“…The production of sugar esters further improves the maximum concentration and stability of the suspended saccharide particles [15][16][17][18][19]. We utilized the solvent-free suspension-based medium in a closed-loop bioreactor system operated under continuous recirculation at 53˝C to prepare sugar esters on a 30 gram scale.…”

Production of Oleic Acid Ethyl Ester Catalyzed by Crude Rice Bran (Oryza sativa) Lipase in a Modified Fed-batch System: A Problem and its Solution

“…The final ester conversion (95.7%) was 1.04 times higher and obtained 2 h earlier than that of using the previous fed-batch system [6]. Moreover, this reaction system also produced a higher final ester conversion than any other esterification reactions using any other fed-batch systems [24,25,26,27].…”