Combined use of two lipases for cheaper biodiesel synthesis

Abstract

In the last two decades the demands o.f fossil fuels have dramatically increased, and expert calculations suggest that there is a serious uncertainty to be exhausted in the near future. Moreover, there are environmental problems associated with burning fossil, like greenhouse gasses, that need to be addressed using different and renewable energy sources instead of fossil fuels. Biodiesel is considered a potential substitute o.f conventio.nal petro-diesel. The alkyl esters of long chain fatty acids (biodiesel) are obtained via transesterification with low molecular weight alcohols of renewable feedstock oils, such as vegetable oils and animal fats. . Current industrial productio.n o.f biodiesel is made with homogenous catalysts and non-edible or waste oils. Commonly used homogenous catalysts are strong bases or acids. They are cheaper than biocatalysts. Basic catalysts are faster than acid catalysts, but they are no.t appropriate for conversion o.f oils with high free fatty acid contents, such as cheap oil feedstocks and waste cooking oils. By contrast, enzymatic catalysts are more selective, have less energetic requirements and do not produce by-products. Saponification problems associated with basic catalysed transesterification of oils are avoided in the biocatalysed process. Immobilized lipases simultaneously catalyse the alcoholysis of all the forms of fatty acids (free and combined with glycerol) (Tan et al., 2010). The absence of soaps formation during the enzyme catalysed production of biodiesel, makes easy, simple and less expensive the biodiesel and glycerol separatio n and recovery. Transesterification and alcoholysis reactions of acylglycerols are also commonly employed for synthesis of partial and structured glycerides or other fatty acid esters with cosmetics and pharmaceutical applications. The enzymatic regio-, chemo- and enantioselectivities of enzymes are key tool for optimal development of new high value products derived from o.il feedstocks (o.mega-3 rich products, milk fat substitutes, etc). Commercial biocatalysts are very expensive compared with chemical catalysts. Researchers are doing important efforts to increase their life time under operational conditions, using technology of genetic engineering and immobilization too.ls. At present, Novozyme 435 and Lipozyme TL 1M are two commercial immobilized lipases that catalyse the synthesis of biodiesel more efficiently (Hernández-Marín & Otero, 2008). These two biocatalysts exhibit different regioselectivities, namely non selective and sn-l,3 regioselectivity, respectively. We also previously demonstrated that these two catalysts have different requirements and distinct behaviour in the synthesis of biodiesel from different oil feedstock. In this work, we have investigated the use of these two commercial lipases in two combined reactors in serie. The purpose of the study was to reduce the impact of the price of the bio.catalyst in the biodiesel product without significant reduction of reaction speed and conversion.