|Hsu, An Fei|
Submitted to: Biotech and Applied Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 20, 2001
Publication Date: March 20, 2002
Citation: HSU, A.C., JONES, K.C., FOGLIA, T.A., MARMER, W.N. IMMOBILIZED LIPASE-CATALYZED PRODUCTION OF ALKYL ESTERS OF RESTAURANT GREASE AS BIODIESEL. BIOTECHNOLOGY APPLIED BIOCHEMISTRY. 2002. V. 36. p. 181-186. Interpretive Summary: Simple alkyl ester derivatives of fats and oils (typically methyl and ethyl esters), when used as diesel engine fuels, are commonly referred to as biodiesel. Although biodiesel has been promoted as a biodegradable and renewable fuel that improves diesel engine emissions, a major impediment to its widespread adoption is its higher cost compared to petro-diesel. Since ethe price of the feedstock represents about 70% of the cost of biodiesel, there is interest in using lower cost feedstocks to produce biodiesel. Recycled restaurant greases command a lower price compared to commodity fats and oils. The use of these materials as feedstocks, however, presents technical difficulties when using conventional methods of preparing biodiesel, which employ inorganic catalysts. Here, we describe an enzymatic approach to the production of biodiesel from recycled greases using immobilized lipases. Compared to current methods, the immobilized enzymes, which can be reused, give higher yields of biodiesel and present fewer processing difficulties. This technology, therefore, has the potential of improving the economics for producing biodiesel from recycled greases.
Technical Abstract: Simple alkyl ester derivatives of restaurant grease were prepared using immobilized lipases as biocatalysts. The lipases studied included Thermomyces lanuganosa and Candida antarctica supported on granulated silica (gran-T.l. and gran. C.a., respectively), Candida antarctica supported on a macroporous acrylic resin (SP435), and pseudomonas cepacia immobilized within a phyllosilicate sol-gel matrix (IM PS-30). All alcoholysis reactions were carried out in solvent-free media employing a one-step addition of the alcohol to the reaction system. Of the lipases studied, IM PS-30 was found to be the most effective in catalyzing the methanolysis and ethanolysis of grease. The processes catalyzed by gran- T.L.and gran-C.a. gave poor conversions to esters, and the SP435-catalyzed reactions gave intermediate yields of ethyl and methyl esters. Water activity (aw) was an important factor in the methanolysis reactions; reaction media with aw < 0.5 resulted in the highest conversions to methyl esters. Molecular sieves also improved methyl ester yields by as much as 20% in transesterification reactions catalyzed by IM PS-30. The immobilized lipases also were evaluated for their ability to produce alkyl esters of grease with several additional normal and branched-chain alcohols.