Conversion of degummed soybean oil to biodiesel fuel with immobilized Candida antarctica lipase

Crude soybean oil did not undergo methanolysis with immobilized Candida antarctica lipase but degummed oil did. Therefore, the substance that was removed in the degumming step was estimated to inhibit the methanolysis of soybean triacylglycerols (TAGs). The main components of soybean gum are phospholipids (PLs), and soybean PLs actually inhibited the methanolysis reaction. In addition, PLs were detected in chloroform/methanol (MeOH) extracts from the immobilized lipase preparation that had been used in the methanolysis of crude soybean oil. These results showed that PLs were at least one of the inhibitory substances in methanolysis of TAGs. The inhibition may due to the interference of the interaction of the lipase molecule with substrates by PLs bound on immobilized preparation. These findings indicated that degummed oil has to be used as a substrate for enzymatic methanolysis. Indeed, three-step methanolysis successfully converted 93.8% degummed soybean oil to its corresponding methyl esters, and the lipase could be reused for 25 cycles without any loss of the activity.