Monday, May 5, 2008
12-14

Assessment the morphological, biochemical and kinetic properties for Candida rugosa lipase immobilized on hydrous niobium oxide to be used in the biodiesel synthesis

M. Miranda1, D. Urioeste1, Maria L. C.P. Silva1, Gisella M. Zanin2, and Heizir F. de Castro1. (1) Engineering School of Lorena, University of São Paulo, P. O. Box 116, Lorena - SP, 12602-810, Brazil, (2) Chemical Engineering Department, State University of Maringa, Av. Colombo, 5790, BL E-46, Maringa - PR, 87020-900, Brazil

Lipase from Candida rugosa (CRL) was successfully immobilized on niobium oxide. The matrix could effectively attached the enzyme, with high retention of activity and prevent its leakage. Following immobilization, CRL exhibited improved storage stability and performed better at higher incubation temperatures. The enzyme retained most of its catalytic efficiency after successive operational cycles. The immobilized derivative (IE) was fully characterized with respect to their morphological properties: particle size, surface specific area and pore size distribution (B.E.T.) and yield of grafting (TG). Structural integrity and conformational changes, such as surface cavities in the support, were observed by SEM. A comparative study between free and immobilized lipases was provided in terms of pH, temperature and thermal stability. The catalytic performance of the IE was also evaluated for the synthesis of biodiesel employing babassu oil and short chain alcohols (ethanol, propanol and butanol). The alcohol carbon chain showed a strong influence on the transesterification performance. As the length of the alcohol carbonic chain increased higher yield and productivity were detected. The highest yield (85%) and productivity (7.5g.L-1.h-1) were attained for butanol and the lowest values (36% and 1.2 g.L-1.h-1) for propanol. No ester formation was detected for the system ethanol/oil and this was attributed to the high polarity of the ethanol (log P <0), which leads to an unfavored partition of water between enzyme and support, thus stripping essential water from enzyme molecules and reducing the activity. The application of this IE was found to be unsuitable for the ethanolysis of babassu oil.

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