Monday, November 9, 2009
P21

Strategies for the Efficient Cr(VI) Removal by Environmental Pichia Strains with Preadapted Inocula

Pablo M. Fernandez1, Maria M. Martorell1, Faustino Sineriz2, Julia I. Fariña1, and Lucia Castellanos2. (1) Fungal Biotechnology, PROIMI-CONICET, Av Belgrano y Pje Caseros, Tucumán, Argentina, (2) Fermentation Department, PROIMI and FBQF, Universidad Nacional de Tucuman, Belgrano y Caseros, Tucumán, Argentina

Cr(VI) bioremediation is specially interesting because of the high toxicity of this metal which is involved in a number of industrial applications and causes environmental pollution. Chromium resistant yeast strains (Pichia jadinii M9 and Pichia anomala M10) isolated from the effluent of a textile factory and selected by their ability for Cr(VI) removal, were precultured in liquid medium amended with 1 mM Cr(VI). Preadapted inocula were used to inoculate a 1 L-working volume bioreactors, in order to determine Cr(VI) removal at different Cr concentrations. A modified YNB medium supplemented with sucrose (50 g/L) and ammonium sulfate (0.6 g/L), with an initial pH value of 5.0 was used. Temperature, pH, agitation and air flow rate were automatically monitored. Biomass dry weight, residual sugars, ammonium and Cr(VI) were measured following conventional protocols. With both yeasts, at 1 mM initial Cr(VI) concentration, growth and metal removal were improved at the higher incubation temperature tested (30ºC), and by moderate aeration and stirring conditions (0.5 vvm/250 rpm). Preadapted inocula were shown to promote higher Cr(VI) removal rates. Cr(VI) disappearance was retarded as initial Cr(VI) concentration increased. At 0.5 mM, P. jadinii M9 and P. anomala M10 required 12 and 8 h for full metal removal, respectively; whilst at 1 mM removal was achieved after 24 h of cultivation, and at 2 mM, 96 and 72 h were necessary. Optimization of the fermentation parameters proposed would be relevant to perform a successful Cr-removal for bioremediation purposes.

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