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Effects of different light spectra on the growth, composition, and productivity of microalgae from 4 different taxa with different pigment profiles

Saefurahman, G. (2015) Effects of different light spectra on the growth, composition, and productivity of microalgae from 4 different taxa with different pigment profiles. Masters by Research thesis, Murdoch University.

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Microalgae are renewable sources for the production of high-value products, biofuels and environmental applications. Microalgae are photosynthetic plant-like organisms with a diversity of light-harvesting pigments. Light is the main limit to the growth of microalgae. However, photosynthesis only uses part of the solar spectrum (400-700 nm) called photosynthetically active radiation (PAR). Characterization of promising species, optimum photosynthetic productivity and efficiency have become a significant aspect in further development of efficient lighting designs/filters for microalgal culture systems. In this study, effects of three different light spectra: white (400-700 nm), blue (407-488 nm), and red (621-700 nm) on the key parameters of Nannochloropsis sp., Botryococcus braunii, Amphora sp., and Pleurochrysis carterae were investigated. The cultures received an equal light energy (2.23±0.10 W.m-2) so that the main effect was the light quality, and were grown and acclimated to the changes of spectral conditions.

All species responded differently to the light spectra in their key parameters, i.e. photosynthetic and respiration rates, growth, biomass, lipid, carbohydrate, protein, chlorophyll content, and productivity. The use of narrower PAR, i.e. blue and red, significantly increased particular parameters in 4 tested species compared to the full spectrum (white light). High photosynthetic rates in particular spectrum were not always followed by a higher growth rate so that the growth of microalgae was not only related to the photosynthesis mechanisms, but also influenced by other cellular processes which are also spectrally dependent. The low levels of oxygen concentration significantly increased the photosynthetic rates of 4 species. This study found that the chlorophyll c containing algae all have heavier cells and higher cellular content of lipid, carbohydrate, and protein under red light. In general, the effects of tested spectra were different and species-dependent based on the variability of pigment profiles, absorption and action spectra, photoregulation of enzymes, chromatic adaptation, and photoacclimation responses.

Item Type: Thesis (Masters by Research)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Borowitzka, Michael, Moheimani, Navid and Cord-Ruwisch, Ralf
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