Sunday, April 29, 2007

Immobilization of Candida antarctica lipase B by adsorption on green coconut fiber

Ana Iraidy Santa Brigida, Álvaro Daniel Teles Pinheiro, Andrea Lopes de Oliveira Ferreira, and Luciana R. B. Goncalves. Chemical Engineering, Universidade Federal do Ceará, Campus do Pici, Bloco 709, Fortaleza, Brazil

The use of immobilized enzymes offers some advantages over suspended enzymes, such as reutilization, avoiding lost and reducing the cost of recuperation. However, cost of support and immobilization reagents may be an economical drawback. In this context, many researches have sought for inexpensive support matrixes to enzyme immobilization. Meanwhile, in Brazil, an effort is being made to find alternative uses to green coconut husk, an agroindustrial waste. Therefore, the present study investigates the feasibility of using green coconut fiber for the immobilization of Candida antarctica lipase B by adsorption. The effect of different variables on adsorption process have been studied, such as: lipase loading, contact time, pH of the coupling media, kinetic parameters and pH of the support surface. A stable immobilized enzyme was obtained by contacting coconut fiber washed with water (surface pH = 5) with an enzyme solution containing 40 U/mL in sodium phosphate buffer (pH 7.0) for 2h at room temperature. The thermal stabilization factor at 60ºC was 92.15. After four cycles of hydrolysis, the immobilized enzyme kept 40% of the initial activity. Michaelis-Menten Kinetic parameters were the same for both immobilized and soluble enzymes (Km = 120.62 ± 15.42 mM and Vmáx = 0.3029 ± 0.021 mM/min). Due to influence of the pH of coupling media on enzyme adsorption, electrostatic forces are the driving force of the immobilization process.