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Tissue culture of Australian brown seaweeds and an assessment of their tocopherol content

Lawlor, Heather Jane (1989) Tissue culture of Australian brown seaweeds and an assessment of their tocopherol content. PhD thesis, Murdoch University.

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The problems of harvesting phaeophycean algae make it desirable to investigate the possibility of tissue cultures as an alternative source of algal secondary metabolites. Ecklonia radiata was used as a model to develop a procedure for axenic tissue culture of phaeophycean macroalgae, and the method was then applied to species of Cystophora and Sargassum.

In E. radiata, growth from the explant occurred in 2 main forms. Pale yellow or unpigmented cells which grew from the cut surface of the explant could not be excised and grown separately. These cells grew for a limited period in dark culture and their development was inhibited by light. Deeply pigmented cells developed initially from centres within the stipe explants, but later grew freely on the surface of the medium. They grew indefinitely in the light and showed minimal growth in the dark. Both types of cells grew either as filaments or callus. In species of Cystophora, unpigmented growth was most common, but pigmented filaments and callus were initiated from explants of C. siliquosa and C. retorta. Only unpigmented callus was seen in Sargassum sp. Tissue cultures of E. radiata regenerated sporophytelike thalli from both unpigmented and pigmented cells, but this occurred rarely.

Heterotrophic growth of the cultures was not achieved despite the addition to the medium of a wide range of organic carbon compounds, vitamins and growth regulators. Best growth of E. radiata tissue cultures was on media modified from Provasoli's enriched seawater (1968) or Murashige and Skoog medium (1962), based on seawater (75%), with nitrate, filter sterilised vitamins, and 2,4-D (10 βM). The concentration of agar or nitrate in the medium, or the addition of seaweed extract, changed the morphology of the cultures.

The tocopherol content of E. radiata, Acrocarpia sp., Caulocystis sp. and 11 species of Cvstophora was investigated. High pressure liquid chromatography was used for the analysis of tocopherol isomers. In the Fucaceae (Cvstophora, Acrocarpia and Caulocystis) there was a high total tocopherol content (e.g., 1130 βg tocopherol g-1 dry weight in C. retroflexa), and high ratio of non- γtocopherols relative to γ-tocopherol (e.g., 30 βg r-, 453 βg β- plus γ-, and 463 βg δ-tocopherol g-1 dry weight in Acrocarpus sp.). The levels exceed those of the leaves of higher plants and other macroalgae, and are only surpassed by the content of seeds from some higher plants, and by certain microalgae.

Analysis of C. siliquosa pigmented tissue cultures showed that tocopherols were also produced in vitro. The total tocopherol content in these cultures was similar to that described in the literature for safflower cell cultures.

The results demonstrate that macroalgae are an important source of vitamin E. They also indicate the potential of cell culture of phaeophycean macroalgae for the selection and multiplication of cell lines with commercial value. Before the full potential of cell culture can be realised, the problem of the requirements for indefinite rapid heterotrophic growth of undifferentiated cultures must be solved.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): McComb, Jen and Borowitzka, Michael
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