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The continous production of ethyl esters of grease using a phyllosilicate sol-gel immobilized lipase from Burkholderias cepacia (IM BS-30) as catalyst was investigated. Enzymatic transesterification was carried out in a recirculating packed-column reactor using IM BS-30 as the stationary phase and ethanol and restaurant grease as the substrates without solvent. The bioreactor was operated at various temperatures (40–60°C), flow rates (5–50 mL/min), and times (8–48 h) to optimize ester production. Under the optimal operating conditions (flow rate, 30 mL/min; temperature, 50°C; mole ratio of substrates, 4∶1 ethanol/grease; reaction time, 48 h), the ester yields were >96%. The IM BS-30 could be reused in the reactor for continous ester production. The conversion of grease to ester was monitored by HPLC and GC, whereas free and total glycerol content in the product was determined by GC. Either water-washing or silica column chromatography reduced the free and total glycerol content of the ethyl ester preparation to acceptable levels. |
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