Enzymatic transesterification of waste vegetable oil to produce biodiesel

• Lipase transesterification of refined and waste vegetable oils was studied.
• Ethanol was added in three steps in order to prevent inhibitory effects.
• The effect of two cooking treatments on reaction performances was analysed.
• The influence of different initial biocatalyst/oil ratios on final conversion was observed
• Biocatalyst was recovered, washed and reused in six reaction cycles in sequence.

An experimental study on enzymatic transesterification was performed to produce biodiesel from waste vegetable oils.Lipase from Pseudomonas cepacia was covalently immobilized on a epoxy–acrylic resin support. The immobilized enzyme exhibited high catalytic specific surface and allowed an easy recovery, regeneration and reutilisation of biocatalyst.Waste vegetable oils – such as frying oils, considered not competitive with food applications and wastes to be treated – were used as a source of glycerides. Ethanol was used as a short chain alcohol and was added in three steps with the aim to reduce its inhibitory effect on lipase activity.The effect of biocatalyst/substrate feed mass ratios and the waste oil quality have been investigated in order to estimate the process performances. Biocatalyst recovery and reuse have been also studied with the aim to verify the stability of the biocatalyst for its application in industrial scale.