Comparative analysis of immobilized biocatalyst: study of process variables in trans-esterification reaction.

This study deals with an experimental investigation into the trans-esterification behavior of two biocatalysts produced by different immobilization techniques of the same lipase from Pseudomonas cepacia. Biocatalysts catalyzed trans-esterification of commercial frying oil. It was verified that no enzyme leaching occurs and stepwise addition of ethanol is needed to improve the process performance. When stoichiometric ethanol has been added completely at the beginning of the reaction, percent mass fraction of esters reached 33% after 9 h and 52% after 30 h. Instead, when ethanol has been added in steps, ester production gradually increased at any time. Moreover, different amounts of biocatalyst were added to the reaction system and it was found that it is not necessary to add more than 3% of biocatalyst with respect to the oil mass to avoid inhibition. The immobilization method influences the reaction progress and the intermediate-glyceride profiles were analyzed. Results showed that the two biocatalysts have the same affinity towards triglycerides, but the covalently immobilized lipase (epobond P. cepacia) has a lower affinity towards diglycerides and monoglycerides and, in general, a lower activity than the absorbed lipase (lipo P. cepacia).

Enzymatic transesterification of waste vegetable oil to produce biodiesel.

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.