Journal of Industrial Microbiology and Biotechnology

, Volume 33, Issue 6, pp 408–416

Effect of n-dodecane on Crypthecodinium cohnii fermentations and DHA production

  • Teresa Lopes da Silva
  • Ana Mendes
  • Rui L. Mendes
  • Vítor Calado
  • Sebastião S. Alves
  • Jorge M. T. Vasconcelos
  • Alberto Reis
Original Paper

DOI: 10.1007/s10295-006-0081-8

Cite this article as:
Silva, T.L.., Mendes, A., Mendes, R.L. et al. J IND MICROBIOL BIOTECHNOL (2006) 33: 408. doi:10.1007/s10295-006-0081-8

Abstract

The potential use of n-dodecane as an oxygen vector for enhancement of Crypthecodinium cohnii growth and docosahexaenoic acid (DHA) production was studied. The volumetric fraction of oxygen vector influenced the gas–liquid volumetric mass transfer coefficient kLa positively. The kLa increased almost linearly with the increase of volumetric fraction of n-dodecane up to 1%. The stirring rate showed a higher influence on the kLa than the aeration rate. The effects of this hydrocarbon on C. cohnii growth and DHA production were then investigated. A control batch fermentation without n-dodecane addition (CF) and a batch fermentation where n-dodecane 1% (v/v) was added (DF) were carried out simultaneously under the same experimental conditions. It was found that, before 86.7 h of fermentation, the biomass concentration, the specific growth rate, the DHA, and total fatty acids (TFA) production were higher in the CF. After this fermentation time, the biomass concentration, the DHA and TFA production were higher in the DF. The highest DHA content of biomass (6.14%), DHA percentage of TFA (51%), and DHA production volumetric rate rDHA (9.75 mg l−1 h−1) were obtained at the end of the fermentation with n-dodecane (135.2 h). The dissolved oxygen tension (DOT) was always higher in the DF, indicating a better oxygen transfer due to the oxygen vector presence. However, since the other C. cohnii unsaturated fatty acids percentages did not increase with the oxygen availability increase due to the n-dodecane presence, a desaturase oxygen-dependent mechanism involved in the C. cohnii DHA biosynthesis was not considered to explain the DHA production increase. A selective extraction through the n-dodecane was suggested.

Keywords

Crypthecodiniumcohniin-DodecanekLaDHA production and CSTR

Abbreviations

CF

Control batch fermentation without n-dodecane

CSTR

Continuous stirred tank reactor

DF

Batch fermentation with n-dodecane 1% (v/v)

DHA

Docosahexaenoic acid (22:6ω3)

DOT

Dissolved oxygen tension

DPM

Dynamic pressure method

kLa

Gas–liquid volumetric mass transfer coefficient (h−1)

PUFA

Polyunsaturated fatty acids

TAG

Triacylglycerols

TFA

Total fatty acids

rDHA

DHA production volumetric rate (g l−1 h−1)

rpm

Rotations per minute

rTFA

TFA production volumetric rate (g l−1 h−1)

vvm

Volume of gas per volume of aerated liquid per minute

Copyright information

© Society for Industrial Microbiology 2006

Authors and Affiliations

  • Teresa Lopes da Silva
    • 1
  • Ana Mendes
    • 1
  • Rui L. Mendes
    • 2
  • Vítor Calado
    • 1
  • Sebastião S. Alves
    • 3
  • Jorge M. T. Vasconcelos
    • 3
  • Alberto Reis
    • 1
  1. 1.Instituto Nacional de Engenharia, Tecnologia e Inovação, Departamento de BiotecnologiaUnidade de Bioengenharia e BioprocessosLisboaPortugal
  2. 2.Instituto Nacional de Engenharia, Tecnologia e Inovação, Departamento de Energias RenováveisUnidade de BiomassaLisboaPortugal
  3. 3.Instituto Superior Técnico, Departamento de Engenharia Química e BiológicaCentro de Engenharia Biológica e QuímicaLisboaPortugal