Monday, May 5, 2008
7-55

Lipase production of  Aspergillus parasiticus by solid state fermentation

Laila C. Cortás, Melissa L. E. Gutarra, Valéria F. Soares, and Denise M.G. Freire. Departamento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

The solid-state fermentation (SSF) appears as an interesting low-cost alternative for the production of enzymes. Additionally, low-cost, abundant materials of vegetal origin, such as agroindustrial wastes (soy cake, wheat bran, sugar cane bagasse, etc.) can be employed as raw materials. The present investigation reports the production, and characterization of lipase of an Aspergillus parasiticus strain.  Initially, the kinetic study experiments were carried out using babassu cake as basal solid medium moisturized with water (70%,w/v) without supplementation or with 3.3%(w/w) sugar cane molasses showing higher activities on babassu cake without supplementation in 72h of fermentation at 30°C. The influence of inoculum concentration, temperature and moisture on enzyme production was evaluated employing statistical experimental design, and an empirical model was adjusted to the experimental data. The last two variables were found to be the most significant in the process. It was shown that higher lipase activities could be achieved at lower temperatures and moisture. The maximum lipase activity was obtained at the temperature of 28°C and moisture of 65% (w/v). The substrate specificity of the crude lipase was determined using several p-nitrophenyl as substrate. Higher Vmax and lower Km were obtained with p-nitrophenyl butyrate indicating that this enzyme presents high affinity for short-chain esters. The immobilized lipase in hydrophobic support (acurel) also catalyzes the synthesis of ethyl oleate. Thus the lipase production by SSF using an abundant and low cost agroindustrial residue as culture medium, showed high biotechnological potential.

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