Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2004
Publication Date: September 1, 2004
Citation: Hsu, A., Jones, K.C., Foglia, T.A., Marmer, W.N. 2004. Continuous production of ethyl esters of grease using an immobilized lipase. Journal of the American Oil Chemists' Society. 81(8):749-752. Interpretive Summary: The simple mono-alkyl esters of vegetable oils and fats (typically methyl and ethyl esters) when used as diesel engine fuels are commonly referred to as biodiesel. Due to the high cost of biodiesel production, there is a growing attention to making biodiesel from less expensive agricultural feedstocks. This in turn demands new methods of production, one of which is a biocatalytic approach, the use of an immobilized enzyme. Use of a biocatalyst must be adaptable to a continuous process for biodiesel production. In this paper, we describe the production of biodiesel in a bioreactor using immobilized lipase enzymes under optimized conditions of temperature, solvent, and amount of enzyme used. The technology has potential application in the commercial production of biodiesel from such feedstocks as spent restaurant grease and ethanol.
Technical Abstract: The continuous production of ethyl esters of grease using a phyllosilicate sol-gel immobilized lipase from Pseudomonas cepacia (IM PS-30) as catalyst was investigated. Enzymatic transesterification was carried out in a recirculating packed column reactor using IM PS-30 as the stationary phase and ethanol and restaurant grease as the substrates without solvent. The bioreactor was operated at various temperatures (40-60 deg. C), flow rates (5-50 mL/min), and times (8-48 h) to optimize ester production. Under the optimum operating conditions (flow rate, 30 mL/min; temperature, 50 deg. C, mole ratio of substrates, 4:1, ethanol:grease; reaction time 48 h) the ester yields were >96%. The IM PS-30 could be reused in the reactor for continuous ester production. The conversion of grease to ester was monitored by high performance liquid chromatography and gas chromatography while glycerol content in the product was determined by gas chromatography. Either water washing or silica column chromatography purified the ethyl esters so that the glycerol content was not detectable.