title: Effectiveness factor in biological external convection: study in high viscosity systems.
abstract: A study regarding the influence of mixing on the efficiency of alginate and xanthan synthesis was carried out. The effectiveness of these two systems in terms of a dimensionless reaction convection number (N(RC)), which is a function of the power input per unit volume, was analysed and compared with low viscosity systems. The results revealed that a decrease in the power input caused a reduction in the growth rate as well as in production rate. It was observed that the effectiveness factor (eta) both for alginate production and xanthan synthesis resulted weakly dependent on the biomass content. A good correlation between effectiveness and N(RC) was obtained for the two tested models. N(RC) number could be appropriately employed in correlating the effectiveness factor for processes with viscosities from 0.001 to more than 1 kg m(-1) s(-1). Due to the parallelism with the conventional internal diffusion approach (Thiele modulus), the advantages for applying N(RC), in particular to correlate the efficiency in systems limited both for external convection and internal diffusional resistance, are shown.
authors.affiliation: Department of Bioengineering, Institute of Biotechnology, National University of México, Apdo. Post. 510-3, Cuernavaca, 62250 Morelos, Mexico.
authors.forename: C
authors.initials: C
authors.lastname: Peña
authors.forename: E
authors.initials: E
authors.lastname: Galindo
authors.forename: M
authors.initials: M
authors.lastname: Díaz
mesh_terms: D000464:Alginates / Q000378:metabolism*; D016948:Azotobacter vinelandii / Q000254:growth & development / Q000378:metabolism; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D001709:Biotechnology / Q000379:methods; D018929:Cell Culture Techniques / Q000379:methods; D018481:Convection; D004058:Diffusion; D005285:Fermentation; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D007218:Industrial Microbiology / Q000379:methods*; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000378:metabolism; D012212:Rheology; D013696:Temperature; D014783:Viscosity; D016959:Xanthomonas campestris / Q000254:growth & development / Q000378:metabolism
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D011135:Polysaccharides, Bacterial; D020723:Glucuronic Acid; C002563:xanthan gum