Solvent effect on the enzymatic production of biodiesel from waste animal fat

Waste animal fat is a promising feedstock to replace vegetable oil in commercial biodiesel process, however the high content of free fatty acid in waste fat makes it unfeasible to be processed with commercial base-catalytic process. Enzymatic process in supercritical fluid is a promising way to convert waste fat into biodiesel since enzyme can catalyze both esterification of free fatty acid and transesterification of triglyceride while supercritical fluid overcome mass-transfer limitation. However, the glycerol by-product needs to be separated because it might reduce the enzyme activity. Organic solvent can be used to extract the glycerol from the enzyme with destructive effect to the enzyme. Thus, the destructive effect of organic solvent on the ability of modified C.antarctica lipase B to produce biodiesel from the waste fat was investigated. And the reversibility of enzyme was tested by various ways, drowning by organic solvents, and reuse after non-solvent experiment. The activity of enzyme was considerably affected by organic solvents. The solvent-drowning test showed that the yields were similar or higher that non-solvent case. This implies that the solvent itself did not cause the permanent change in enzyme structure to decrease activity. The decrease in yield was observed in the reuse test, which is regarded to be caused by the incomplete removal of products from the first run. (C) 2018 Elsevier Ltd. All rights reserved.