Sources and resources: importance of nutrients, resource allocation, and ecology in microalgal cultivation for lipid accumulation

Abstract

Regardless of current market conditions and availability of conventional petroleum sources, alternatives are needed to circumvent future economic and environmental impacts from continued exploration and harvesting of conventional hydrocarbons. Diatoms and green algae (microalgae) are eukaryotic photoautotrophs that can utilize inorganic carbon (e.g., CO2) as a carbon source and sunlight as an energy source, and many microalgae can store carbon and energy in the form of neutral lipids. In addition to accumulating useful precursors for biofuels and chemical feed stocks, the use of autotrophic microorganisms can further contribute to reduced CO2 emissions through utilization of atmospheric CO2. Because of the inherent connection between carbon, nitrogen, and phosphorus in biological systems, macronutrient deprivation has been proven to significantly enhance lipid accumulation in different diatom and algae species. However, much work is needed to understand the link between carbon, nitrogen, and phosphorus in controlling resource allocation at different levels of biological resolution (cellular versus ecological). An improved understanding of the relationship between the effects of N, P, and micronutrient availability on carbon resource allocation (cell growth versus lipid storage) in microalgae is needed in conjunction with life cycle analysis. This mini-review will briefly discuss the current literature on the use of nutrient deprivation and other conditions to control and optimize microalgal growth in the context of cell and lipid accumulation for scale-up processes.

Enhance Growth and Biochemical Composition of Nannochloropsis oceanica, Cultured under Nutrient Limitation, Using Commercial Agricultural Fertilizers

“…Until now, there is no recorded data available about using of nitric acid as nitrogen source in medium composition of marine microalga N. oceanica. To date, nitrate is a commonly studied as a nitrogen source used to understand nutrient limitation to induce lipid accumulation [24]. In the current study, we compare ammonium sulphate and nitric acid, as CAGF nitrogen sources, with sodium nitrate used in F/2 medium.…”

Characterization of newly isolated oleaginous microalga Monoraphidium sp. for lipid production under different conditions

“…Urea is a commercially available nitrogen source being used in agriculture for cultivation of crops because of its universal availability and affordability [31][32][33]. Furthermore, this shows that the fatty acid compositions can be feasibly influenced by the accumulative effect of environmental growth condition, which can regulate the various metabolism involved in fatty acid synthesis [34,35].…”

A euryhaline Nannochloropsis gaditana with potential for nutraceutical (EPA) and biodiesel production

“…However, at a very low concentration of chlorophyll-a, carotenoids were abundantly found in the pitch-dark period. The dominant fatty acids (C16:0, C16:1 and C20:5) in terms of composition (%) varied with changes in the photoperiod, which may be due to the availability of different precursors for fatty acid metabolism and their concentration [19,20].…”

“…The set of more than one abiotic factor resulted in different fatty acid compositions [19]. ∑SFA and ∑MUFA are considered very important for biodiesel production [26].…”