Effect of phospholipids on free lipase-mediated methanolysis for biodiesel production

• Free lipase from A. niger was used for enzyme-mediated biodiesel production.
• Free lipase can effectively catalyze the conversion of oil containing phospholipids.
• Free lipase exhibited better reuse stability in the presence of phospholipids.
• The phospholipids were broken down by lipase in the process.
• The final methyl ester phase met the phosphorous demand of biodiesel standard.

Free lipase-mediated alcoholysis offers an effective alternative approach to biodiesel production due to its merits of faster reaction rate and lower preparation cost. Further promoting the application of free lipase in catalyzing the transesterification of crude renewable oils is of significance since the cost of oil feedstock accounts for a major part in biodiesel production. Crude renewable oils typically contain a certain amount of phospholipids and it has been found that the phospholipids have inhibitory effect on lipase's catalytic performance during immobilized lipase-catalyzed biodiesel production. However, the influence of phospholipids on free lipase-mediated alcoholysis in oil/water biphasic system has not been reported. In this work, free lipase from Aspergillus niger was employed as the catalyst for biodiesel production and the effect of phospholipids on free lipase's catalytic performance was explored for the first time. It was found that both the reaction rate and the final FAME content increased and the free lipase exhibited better reuse stability in the presence of phospholipids. Further study on the distribution of phosphorous showed that within 2% phospholipids contained in the oil feedstock, only less than 4 ppm phosphorous remained in the final methyl esters, which well met the phosphorous demand of biodiesel standard. The above results demonstrated that free lipase-mediated alcoholysis was promising for biodiesel production especially with low quality crude vegetable oils as the feedstock.

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