Immobilization of Lipases on Corn Cob Granulate - New Key Technology for Biodiesel Production
The project directly aims to use lipases as heterogeneous catalysts for esterification and transesterification of fatty acids and triglycerides. Lipases are of high importance as biocatalysts. However, for cheap bulk products like biodiesel they are too expensive for single use. Therefore the immobilization of the enzymes seems to be the best solution. Yet, commercially available immobilized lipases are even high priced too. The vegetable by-product corn cob granulate offers a reasonable alternative. Corn cob granulate shows excellent adsorption characteristics. This suggests that the use of lipases immobilized on corn cob granulated material as biocatalysts for the production of biodiesel and other esters with higher alcohols is possible. Classical methods for the production of fatty acid methyl esters use alkaline catalysts. They need to be neutralized at the end of the reaction forming salts which have to be disposed. By the use of biocatalysts reduction of waste can be achieved.
21 crude lipases were screened for their activity in the transesterification reaction of rapeseed oil in solution and suspension. The three most promising lipases were chosen for evaluation of immobilization techniques. The method, which proved to be the most appropriate, is based on adsorption. The transesterification experiments were done in laboratory scale. The influence of parameters like reaction time and reaction temperature, oil-methanol ratio and the amount of immobilized lipase were tested. After this a concept for the continuous process with a self constructed laboratory apparatus was developed. Removement of by product glycerol of the reaction mixture is required. The last working step included the process assessment, evaluation criterions were examined from ecological and economical point of view. The comparative ecological assessment for the existing biodiesel process and the application of lipases, which are immobilized on corn cob granulate, was done by the Sustainable Process Index. For any new technological development it is important not only to meet engineering feasibility, but also to evaluate the economical aspects. The price of the lipases and their life time are the most crucial parameters in the economical viability of the new process. The new developed process of biodiesel production shows to be economically competitive to the classical methods. Overall the enzymatic biodiesel production has been confirmed as a key technology, because it is universally useable for a large number of raw materials and alcohols and thus contributes to a lasting use of natural resources.
Univ.-Prof. Dr. Martin Mittelbach
Institut für Chemie, Karl Franzens Universität Graz
Tel.: +43 (0)316 380-5353
Fax: +43 (0)316 380695353