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Growth and lipid production of Phaeodactylum tricornutum bohlin in a tubular-photobioreactor

Chrismadha, Tjandra (1993) Growth and lipid production of Phaeodactylum tricornutum bohlin in a tubular-photobioreactor. Masters by Research thesis, Murdoch University.

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The current demand on microalgae as a source of high nutritive food/feed and of various fine chemicals has led to a requirement of algal culture system with highly defined conditions to enhance the productivity and produce quality products. Tubular-photobioreactors are such a system. In this study a helical tubular-photobioreactor is used to study the diatom Phaeodactylum tricomutum Bohlin; an alga with a high eicosapentanoic acid [EPA; 20:5 (n-3) fatty acid] content.

The alga was grown successfully in the tubular-photobioreactor with adequate mixing with a centrifugal pump, which did not damage the algal cells. In the reactor the algae are carbon limited, and C02 should be added to enhance the algal growth rate. Other factors, such as nutrients, temperature and irradiance have much smaller effect on the algal growth rate than C02 addition.

The composition of Phaeodactylum tricomutum grown in the tubularphotobioreactor is 30 - 60 % protein, 13 - 42 % carbohydrate and 17 - 46% lipid. The major fatty acids are 14:0, 16:0, 16:1 and 20:5, and EPA make up 12 - 41 % of the total fatty acids.

Various growth factors, including growth phase, nutrients, irradiance and temperature and 5 % C02 addition, markedly affect the algal organic composition and fatty acid composition. An increase in the lipid and EPA content was achieved with N-limitation, and as the N-hmitation did not significantly affect the algal growth rate and biomass output rate, the lipid and EPA productivity were enhanced. When growth condition do not significantly affect the algal lipid and EPA content, the lipid and EPA productivity are positively correlated with the growth rate and culture cell density, and the lipid and EPA productivity are enhanced at optimum conditions that support a high growth rate, such as optimum nutrient conditions, high irradiance and 5 % C02 aeration.

This study suggest that there are two possible ways to enhance lipid and EPA production from Phaeodactylum tricomutum in the tubularphotobioreactor. Firstly by inducing culture conditions, such as N-limitation, that stimulate the lipid and EPA production without decreasing the algal growth rate and biomass concentration, and by providing the culture with optimum conditions to stimulate high growth rates, while the lipid and EPA content remained relatively constant, such as obtained with 5 % C02 aeration.

Item Type: Thesis (Masters by Research)
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): Borowitzka, Michael
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