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Comparative analysis of mixing distribution in aerobic stirred bioreactor for simulated yeasts and fungus broths

  • Original Paper
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Journal of Industrial Microbiology & Biotechnology

Abstract

The study on mixing distribution for an aerobic stirred bioreactor and simulated (solutions of carboxymethylcellulose sodium salt), yeasts (S. cerevisiae) and fungus (P. chrysogenum pellets and free mycelia) broths indicated the significant variation of mixing time on the bioreactor height. The experiments suggested the possibility to reach a uniform mixing in whole bulk of the real broths for a certain value of rotation speed or biomass concentration domain. For S. cerevisiae broths the optimum rotation speed increased to 500 rpm with the biomass accumulation from 40 to 150 g/l d.w. Irrespective of their morphology, for fungus cultures the existence of optimum rotation speed (500 rpm) has been recorded only for biomass concentration below 24 g/l d.w. The influence of aeration rate depends on the apparent viscosity/biomass concentration and on the impellers and sparger positions. By increasing the apparent viscosity for simulated broths, or biomass amount for real broths, the shape of the curves describing the mixing time variation is significantly changed for all the considered positions. The intensification of the aeration induced the increase of mixing time, which reached a maximum value, decreasing then, due to the flooding phenomena. This variation became more pronounced at higher viscosities for simulated broths, at higher yeasts concentration, and at lower pellets or filamentous fungus concentration, respectively. By means of the experimental data and using MATLAB software, some mathematical correlations for mixing time have been proposed for each broth and considered position inside the bioreactor. These equations offer a good agreement with the experiment, the maximum deviation being ±7.3% for S. cerevisiae broths.

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Abbreviations

C X :

biomass concentration (g/l d.w.)

d :

stirrer diameter (mm)

N :

impeller rotation speed (s−1)

t m :

mixing time (s)

v S :

superficial air velocity (m/s)

pH∞ :

pH value corresponding to perfect mixing

ΔpH:

pH limits accepted for mixing time determination

α, β, γ, δ:

parameters of empirical correlations (1) and (2)

ηa :

apparent viscosity (Pa.s)

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Authors and Affiliations

  1. Faculty of Industrial Chemistry, Department of Biochemical Engineering, Technical University “Gh. Asachi” of Iasi, D. Mangeron Avenue 71, 700050, Iasi, Romania

    Dan Cascaval

  2. Faculty of Medical Bioengineering, Department of Biotechnology, University of Medicine and Pharmacy, University Street 16, 700115, Iasi, Romania

    Anca-Irina Galaction & Marius Turnea

Authors
  1. Dan Cascaval
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  2. Anca-Irina Galaction
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  3. Marius Turnea
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Correspondence to Dan Cascaval.

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Cascaval, D., Galaction, AI. & Turnea, M. Comparative analysis of mixing distribution in aerobic stirred bioreactor for simulated yeasts and fungus broths. J Ind Microbiol Biotechnol 34, 35–47 (2007). https://doi.org/10.1007/s10295-006-0159-3

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  • DOI: https://doi.org/10.1007/s10295-006-0159-3

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