Optimization of biocatalytic biodiesel production from pomace oil using response surface methodology

Microbial lipase from T. lanuginosus was immobilized onto polyglutaraldehyde-activated olive pomace powder. The support was used to produce biodiesel with pomace oil and methanol. Response Surface Methodology (RSM) in combination with Central Composite Design (CCD) was used to optimize the biodiesel production parameters. Reaction temperature, molar ratio of methanol to oil, biocatalyst content and reaction time were chosen as the variables and the response selected was the yield of pomace oil methyl ester in present work. A quadratic polynomial equation was obtained for pomace oil methyl ester yield by multiple regression analysis. The optimal conditions for the transesterification have been found to be: reaction temperature of 40 °C, alcohol/oil molar ratio of 5.3:1, biocatalyst content of 5.8% w/w and reaction time of 24 h. The predicted pomace oil methyl ester yield was 92.87% under the optimal conditions. Verification experiment (91.81%) confirmed the validity of the predicted model. Biodiesel yield reached 93.73% by adding water (1% w/w) in reaction medium under the optimal conditions. Immobilized lipase was used to determine operational stability and it indicated that immobilized lipase was stable retaining more than 80% residual activity after being used repeatedly for 10 consecutive batches of pomace oil transesterification.

► Olive pomace powder was used as low-cost support for biodiesel production.
► T. lanuginosus was immobilized onto polyglutaraldehyde-activated olive pomace powder.
► RSM in combination with Central Composite Design was used to optimize the parameters.
► Relationships between parameters and responses were further analyzed systematically.