Sunday, April 29, 2007
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Synthesis of fatty acid alkyl esters using a commercial immobilized lipase

Érika C.G. Aguieiras1, Pollyanna T.C. Dias1, Mônica A. P. Silva2, and Marta A.P. Langone3. (1) Química Analítica, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, PHLC, IQ, sl 427, Maracanã, Rio de Janeiro, Brazil, (2) Engenharia Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Tecnologia, Escola de Química, sl 211, Rio de Janeiro, Brazil, (3) Química Analítica, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, PHLC, IQ, sl 427, Maracanã, Rio de Janeiro, Brazil

Carboxylic esters derived from long chain fatty acids are biodegradable and find several industrial applications such as, lubricants and surfactants for hydraulic and drilling fluids, as well as in the cosmetic industry. The use of lipases for production of esters of fatty acids offers significant advantages as compared to the conventional acid catalyzed chemical method:  flexibility regarding the substrate, high selectivity, mild process conditions, easy separation of product, and enzyme reutilization. In the present work, the enzymatic synthesis of monoalkyl esters of the oleic acid and palmitic acid (hexadecanoic acid) was studied, using ethanol and butanol in presence of a commercial immobilized lipase (Lipozyme RM IM) in a solvent-free medium. The effects of the alcohol/acid molar ratio, temperature, enzyme concentration and presence of molecular sieves on the initial rate and reaction yield were investigated. For ethanol (81%) and butanol (93%), the largest yield was obtained when the alcohol was in excess (molar ratio alcohol/acid = 5) for reactions with oleic acid.  The largest yield for palmitic esters, ethanol (63%) and butanol (93%), was obtained with molar ratio equal to 2 and 5, respectively. Reutilization of the immobilized enzyme did not work for the synthesis of ethyl hexadecanoate under the optimum conditions mentioned previously. The activity of the enzyme fell drastically after the first batch. However, the stability of commercially available Lipozyme RM IM for the butyl oleate synthesis in solvent free system was high, with yields higher than 90% after 10 cycles.

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