A significant decrease of the yield of steryl esters production via the esterification of sterols and free fatty acids (FFA) present in vegetable oil deodorizer distillates was observed when consecutive batch reactions (24 hr each) were carried out using the same enzyme and under optimal operating conditions. The objective of this work is to identify the causes of such phenomena, in order to avoid or minimize it, allowing for reuse of the Candida rugosa lipase catalyst in consecutive batch reactions. The effect of water activity and glycerol produced by hydrolysis of acylglycerides, on the stability of the enzyme was studied. Results show that these effects were not the main reason for the decrease of yield in consecutive batch reactions. The presence of oxidation products proved to play an important role in the enzyme inactivation. Because of the high concentration of antioxidants (phenolic compounds, squalene, and tocopherols) naturally present in deodorizer distillates, the inactivation of the enzyme was minimized; nevertheless, it could not be avoided. A partial reuse of the enzyme is technically a possible solution, by adding fresh enzyme in the beginning of each batch reaction. Four consecutive batch reactions (24 hr each) were successfully carried out under optimal conditions, keeping a constant yield of steryl esters (SE) production (>85%).
- ENZYMATIC TRANSESTERIFICATION