Monday, May 5, 2008
9-29

A comparison between shaker and bioreactor performance on the kinetic parameters determination for the xanthan gum production

Sandra Faria1, Patricia Angelica Vieira1, Miriam Maria Resende1, Francisca Pessoa de França2, and Vicelma Luiz Cardoso1. (1) Faculty of Chemical Engineering, Uberlândia Federal University, P.O. Box 593, CEP 38400-902, Uberlândia, Brazil, (2) School of Chemical, Rio de Janeiro Federal University, P.O. Box 68502, CEP 21945-970, Rio de Janeiro, Brazil

This work has the purpose of studying the microbial growth and xanthan gum production in fermentations using the specific a strain of Xanthomonas campestris pv. campestris NRRL B-1459, and diluted sugar cane broth. The production medium contained sucrose (15.0, 25.0 or 35.0 g.L-1), yeast extract (3.0 g.L-1), NH4NO3 (0.86 g.L-1), Na2HPO4 (2.2 g.L-1) and KH2PO4 (2.2 g.L-1) were fermented in bioreactor and rotary incubator shaker. In shaker, the fermentations were carried out for 60 h at a constant agitation rate (150 rpm) and temperature (25 ± 1oC) with the initial pH adjusted to 7.0. In bioreactor, the fermentations were done for 24h at 28 ± 1oC, pH 7.2, 800 rpm and 0.5 vvm. The unstructured kinetic model of Weiss and Ollis (1980) was used to determinate the yields (YP/S), the maximum growth specific rate (μmáx.) and the saturation cellular concentration (X*). The parameters values of the model (μmáx., X*, m, λ, α and β) were obtained by non-linear regression technique using a multiresponse algorithm and the integration of the set of differential equations forming the model was carried out using a fourth-order Runge-Kutta algorithm. While μmáx assumed values of 0.142, 0.133 and 0.199 h-1 and the yields obtained were of 0.352, 0.333 and 0.263 g.g-1 in the rotary incubator shaker for sucrose concentrations of 15.0, 25.0 and 35.0 g.L-1, respectively, those in bioreactor were 0.436, 0.458 and 0.488 h-1 (μmáx) and 0.280, 0.580 and 0.430 g.g-1 (YP/S). The results presented show good correlation with the predictions supplied by the model.

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