Effects of Particle Size of Sucrose Suspensions and Pre-incubation of Enzymes on Lipase-Catalyzed Synthesis of Sucrose Oleic Acid Esters

The effects of high-speed homogenization, high-intensity ultrasound, and their combination were evaluated for the reduction of the particle size of sucrose crystals to enhance solvent-free lipase-catalyzed synthesis of sucrose oleate at 65 degrees C. The combination of homogenization and ultrasound greatly decreased the particle size of suspended sucrose crystals in mixtures of oleic acid/sucrose oleate (86 wt% monoester and 14 wt% diester at a ratio of 90/10 w/w) from 88 to 18 mu m. The suspension-based medium was charged to a stirred tank bioreactor that also contained immobilized lipase from Rhizomucor miehei or Candida antarctica (Lipozyme (R) IM and Novozym (R) 435, respectively; Novozymes, Franklinton, NC, USA), that was pre-incubated in oleic acid for several different temperatures (23-60 degrees C), durations (4-24 h), and stir rates (50-400 rpm, radius of 3 cm), prior to use. The optimal performance was achieved using C. antarctica lipase (83.3 wt% ester, consisting of 46 wt% monoester) in the presence of molecular sieves (18 wt%). The low water concentration (similar to 0.12 wt%) did not affect the activity of C. antarctica lipase.