Optimisation of fatty acid production by selected microalgae for high-value applications
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Microalgae synthesize and produce large amounts of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), with eicosapentaenoic (EPA, 20:5 n-3) and docosahexaenoic (DHA, 22:6 n-3) acids being of particular interest. This project contributes to a larger investigation into the potential of marine-algal-derived PUFAs, as dietary elements for health maintenance and disease prevention. Focus is made on microalgal n-3 LC-PUFA as a sustainable alternative to the traditional fish oil production. The influence of environmental factors on microalgal bio-chemical composition, and optimum culture conditions were determined to achieve a balance between n-3 LC-PUFA accumulation and efficient growth rate. Research involved the assessment of the temperature impact on n-3 LC PUFA productivity and fatty acid composition within eight microalgal-species. N. oculata and I. galbana were further examined under different photoperiod and nutrient conditions. Investigations into potential effects of an adaptive laboratory evolution (ALE) through selec-tive stress exposure (low light), on N. oculata were performed, to achieve higher EPA productivity. The performances of a large-scale production of N. oculata and I. galbana, when cultured in a flat panel photobioreactor were evaluated, examining the culture parameters and health, fatty acid productivity performances and profiles of the two species. The results indicate species-specific responses to abiotic factors and demonstrate the importance of both growth conditions and time of harvesting for maximum EPA and DHA productivity. These compounds displayed variability, with shifts in the concentrations and repartition observed in response to environmental parameters, particularly temperature, nutrient concentration and photoperiod. The impact of such factors on n-3 LC PUFA metabolism were likely to be caused by their effect on key components involved in the expression and regulation of their biosynthetic pathway, as well as their degradation, storage and repartition. ALE resulted in a strain displaying improved features and great potential for natural strain improvement. Compared to laboratory scale results, upscaling displayed no loss of yield in terms of EPA and DHA productivity and biomass. The importance of n-3 LC PUFA, particularly EPA and DHA from microalgae species, to provide functional food for human consumption is now strongly established, and production can be triggered at an environmental level as a result of several degree of fluctuations. The results attained here provide a solid element of valuable scientific information upon which future research can be established.