Special Abstracts / Journal of Biotechnology 150S (2010) S1–S576 S395 in sufficient amount for the commercial exploitation. Therefore, in order to promote the emergence of this industry, it is impor- tant to establish recovery methods for polysaccharides production with commercial interest. Actually the main studies for the produc- tion of sulphated polysaccharide fractions are carried out using low concentration of HCl with reaction periods times of about 1-3 hours. The aim of the present work was to evaluate the sulphated polysaccharides (fucoidan) recovery from brown seaweeds by microwave-assisted extraction under different operational condi- tions. Brown seaweeds species Fucus vesiculosus and Ascophyllus nodosum from North Portugal were studied. The extraction reac- tions were performed according to experimental designs varying the time (1 to 11 min), pressure (30 to 50 psi) and alga/water rela- tion (1/25 to 5/25 g/ml). All the experiments were carried out in a microwave digestion oven MDS-2000 (CEM Corporation). Total sugars content, monosaccharide composition and sulphated con- tent were quantified. Significant differences (p < 0.05) were found varying the pres- sure and time levels, while the alga/water relation did not influence the extraction values in the range of values studied. The, high- est recovery index was achieved when using 50 psi during 11 min. The maximum yield of sulphated polymer extracted under these conditions was similar to values reported in the literature. Monosaccharide composition analyses showed mainly the pres- ence of fucose and galactose. In conclusion, microwave-assisted extraction under short reac- tion times is an effective method in improving polymer dissolution of sulphated polysaccharides from brown seaweeds. doi:10.1016/j.jbiotec.2010.09.508 [P-I.143] Development of an empirical correlation for Newtonian and non-Newtonian fluids in a stirred tank reactor, to predict oxygen mass transfer rates S. Raposo, F. Azevedo, M.E. Lima-Costa ∗ University of Algarce-CIMA, Portugal Keywords: Oxygen transfer; Empirical correlation; Non-Newtonian fluids; Stirred tank reactor Most of animal and plant cell cultures present a non-Newtonian behaviour that has a deep effect on the technological performance of bioreactors, affecting the pattern of mixing, the power input required and on the mass and energy transfer as well. In aerobic cultures, the oxygen mass transfer is still a bottleneck, particu- larly at industrial scale-up, where the high-cell-density biomass and production of metabolites provoke the increase on the vis- cosity culture, lowering the production yield and eventually losing economical process viability. The objective of this work was to contribute for the prediction of oxygen transfer rate in no-Newtonians fluids, given its relevance in cell cultures and the fact that the available empirical equations have no universal applicability. The comparison with Newtonians fluids will be also carried on. The volumetric oxygen mass transfer coefficient (k L a) was deter- mined by the static method in a stirred tank reactor (3 and 7-l) at distinct operating conditions (agitation and aeration), with differ- ent impellers, Rushton turbine and marine propeller, in Newtonian and non-Newtonian fluids. It was also measured the K L a, in a stirred tank reactor (STR), with the combination of those impellers. The combination of marine impeller in the bottom position and Rush- ton turbine on top position in the tank, assured the highest k L a value of 33,8 h -1 , being apparent optimal mass transfer rate in the tested operational STR conditions. Several empirical correlations were tested (Cooper et al., 1944; Ryu and Humphrey, 1972; Ryu & Humphrey modified; Garcia- Ochoa and Gomez, 1998) and the empirical constants influenced by the increasing agitation speed, aeration flows and apparent vis- cosities were determined. The empirical correlation that fits better the range of k L a values, determined in STR 7-L for Newtonian and non-Newtonian fluids, was the equation proposed by Garcia-Ochoa and Gomez (1998) when was used the porous sparger and the Rush- ton turbine. The empirical correlation is strongly dependent on the impeller geometry. References Cooper, C.M., Fernstrom, G.A., Miller, S.A., 1944. Performance of Agitated Gas-Liquid Contactors. Industrial and Engineering Chemistry. 36, 504–509. Garcia-Ochoa, F., Gomez, E., 1998. Mass transfer coefficient in stirred tank reactors for xanthan gum solutions. Biochemical Engineering Journal. 1, 1–10. Ryu, D.Y., Humphrey, A.E., 1972. A Reassessment of Oxygen Transfer Rates in Antibi- otics Fermentations. J. Ferm. Technol. 50, 424–431. doi:10.1016/j.jbiotec.2010.09.509 [P-I.144] A Kinetics Studies of the Production Rhamnolipids by Pseu- domonas aeruginosa LAMI from Glycerin J.R. Sousa 1,∗ , J.A.C. Correa 2 , J.J.L. Martins 2 , V.M.M. Melo 2 , A.J.G. Cruz 1 , L.R.B. Gonc ¸ alves 2 1 Universidade Federal de São Carlos, Brazil 2 Universidade Federal do Ceará, Brazil Keywords: Rhamnolipids; Kinetics; Glycerin Introduction: The kinetics of biosurfactant production exhibits many variations between the several possible systems to be employed, and few generalizations can be made (Desai and Banat, 1997). Therefore, the objective of this work was to evaluated mathematical models for the rhamnolipid, biomass and glycerol concentration to different C/N ratios Methods: P. aeruginosa LAMI was isolated from crude oil contam- inated soil. Experiments were performed in 250 mL erlenmeyers containing 50-mL of culture media: glycerine 5% (w/v), 0.062 M KH 2 PO 4 , 0.2 g/L Mg 2 SO 4 and pH 7.0. NaNO 3 concentrations were 1,0; 1,45 and 4,0 g/L, C/N ratios of 86, 59 and 21, respectively. 2% (v/v) of cells suspension were inoculated and the erlenmeyers were incubated at 37 ◦ C at 150 rpm for 72 hours. Rhamnolipid concentra- tion was determined according orcinol method (Pham et al., 2004). Biomass and Glycerol concentration were determined according to Rocha et al. (2007). Proposed models (Rodrigues et al., 2006) were fitted to experimental data using Microsoft Excel 2007 (solver) by nonlinear regression Results: Figures 1 to 3 show the obtained results during the fermentation using Pseudomonas aeruginosa LAMI. The estimated mathematical model parameters are in Table 1 Fig. 1. Time behaviours of (A) specific rates and (B) biomass, rhamnolipids and glycerol concentrations during the cultivation of P. aeruginosa LAMI (C/N = 21).