Comparison of oxygen mass transfer coefficient in simple and extractive fermentation systems

Author(s)

Viana Marques, Daniela de Araujo ^[1] ; Torres, Beatriz Rivas ^[2] ; Figueiredo Porto, Ana Lucia ^[3] ; Pessoa-Junior, Adalberto ^[1] ; Converti, Attilio ^[2]

Affiliation

^[1] Univ Sao Paulo, Dept Pharmaceut Technol & Biochem, BR-05508000 Sao Paulo - Brazil

^[2] Univ Genoa, Dept Chem & Proc Engn, I-16145 Genoa - Italy

^[3] Univ Fed Rural Pernambuco, Dept Anim Morphol & Physiol, BR-52171900 Dois Irmaos, PE - Brazil

• Document type: Journal article
• Source: Biochemical Engineering Journal; v. 47, n. 1-3, p. 122-126, DEC 1 2009.
• Web of Science Citations: 11

Abstract

Aeration and agitation are important variables to ensure effective oxygen transfer rate during aerobic bioprocesses: therefore, the knowledge of the volumetric mass transfer coefficient (k(L)a) is required. In view of selecting the optimum oxygen requirements for extractive fermentation in aqueous two-phase system (ATPS), the k(L)a values in a typical ATPS medium were compared in this work with those in distilled water and in a simple fermentation medium. in the absence of biomass. Aeration and agitation were selected as the independent variables using a 2(2) full factorial design. Both variables showed statistically significant effects on k(L)a, and the highest values of this parameter in both media for simple fermentation (241 s(-1)) and extractive fermentation with ATPS (70.3 s(-1)) were observed at the highest levels of aeration (5 vvm) and agitation (1200 rpm). The k(L)a values were then used to establish mathematical correlations of this response as a function of the process variables. The exponents of the power number (N(3)D(2)) and superficial gas velocity (V(s)) determined in distilled water (alpha = 0.39 and beta = 0.47, respectively) were in reasonable agreement with the ones reported in the literature for several aqueous systems and close to those determined for a simple fermentation medium (alpha=0.38 and beta=0.41). On the other hand, as expected by the increased viscosity in the presence of polyethylene glycol, their values were remarkably higher in a typical medium for extractive fermentation (alpha=0.50 and beta=1.0). A reasonable agreement was found between the experimental data of k(L)a for the three selected systems and the values predicted by the theoretical models, under a wide range of operational conditions. (C) 2009 Elsevier B.V. All rights reserved. (AU)