Synthesis of ethyl oleate by esterification in a solvent-free system using lipase immobilized on PDMS-modified nonwoven viscose fabrics

A lipase from the yeast Yarrowia lipolytica was immobilized on a PDMS-modified nonwoven viscose fabric and used in the synthesis of ethyl oleate. The efficiency of immobilization improved to 75.2% when the concentrated lipase slurry (180 mg mL(-1)) was used as the source of lipase. When compared with the original immobilized lipase, the lipase immobilized on the PDMS-modified fabric exhibited more stable catalytic activity over 35 batches; exhibited a 20-fold lower affinity for oleic acid, a 42-fold less ethanol-induced inhibition; could be reused in 10 iterative 5L batch stirred tank reactor processes. When compared to that of free lipase, the pH stability range of immobilized lipase was narrower (pH 6-7 vs pH 5-8); the optimum reaction temperature was higher (40 degrees C vs 37 degrees C); and the thermally more stable (70% vs 5% of activity was retained after pre-incubation for 4h at 45 degrees C). The variation in the activity exhibited in an organic solvent could be correlated to the log P. Catalytic efficiency was similar to 13-fold lower upon excessive lipase immobilization. XPS/ATR-FTIR confirmed the introduction of PDMS onto lipase-immobilized viscose. The simple enzyme immobilization method could potentially be useful for the production of ethyl oleate at an industrial scale. (C) 2015 Elsevier Ltd. All rights reserved.