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Biotechnology and Applied Biochemistry (2002) 36, (181–186) (Printed in Great Britain)

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Immobilized lipase-catalysed production of alkyl esters of restaurant grease as biodiesel

An-Fei Hsu¹, Kerby Jones, Thomas A. Foglia and William N. Marmer

Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038, U.S.A.

Key words: ethyl ester, granulated lipase, methyl ester, phyllosilicate sol-gel immobilized lipase, transesterification.

Abbreviations used: IM PS-30, phyllosilicate sol-gel-immobilized lipase from Pseudomonas cepacia; gran-T.l., granulated silica-supported lipase from Thermomyces lanuginosa; gran-C.a., granulated silica-supported lipase from Candida antarctica; TMOS, tetramethyl orthosilicate; a_w, water activity.

¹To whom correspondence should be addressed(e-mail ahsu@arserrc.gov).

Simple alkyl ester derivatives of restaurant grease were prepared using immobilized lipases as biocatalysts. The lipases studied included those of Thermomyces lanuginosa and Candida antarctica supported on granulated silica (gran-T.l. and gran-C.a., respectively), C. 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 catalysing the methanolysis and ethanolysis of grease. The processes catalysed by gran-T.l. and gran-C.a. lipases gave poor conversions to esters, and the SP435-catalysed reactions gave intermediate yields of ethyl and methyl esters. Water activity (a_w) was an important factor in the methanolysis reactions; reaction media with a_w < 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 catalysed 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.

Received 31 January 2002/13 June 2002; accepted 17 July 2002

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