Growing Microalgae in Acidic Conditions to Produce Valuable Fatty Acids

Greg Howard
22nd May, 2024

Growing Microalgae in Acidic Conditions to Produce Valuable Fatty Acids

Molecular phylogeny of Elliptochloris sp. based on 18S rDNA gene sequence comparisons of the genus Elliptochloris.

Image adapted from: Robles et al. / CC BY (Source)

Key Findings

  • Researchers at the University of Huelva studied the mixotrophic growth of the acid-tolerant microalga Elliptochloris sp. using CO2-enriched air
  • CO2 enrichment significantly boosted the growth and biomass productivity of Elliptochloris sp. in mixotrophic conditions
  • Mixotrophic cultures with CO2-enriched air increased the relative abundance of saturated fatty acids, crucial for biodiesel production
Microalgae, microscopic plants found in both freshwater and marine environments, have garnered significant attention for their potential in sustainable biomass production. This interest stems from their ability to grow rapidly and produce valuable compounds such as lipids, which can be converted into biodiesel. However, large-scale cultivation of microalgae presents several challenges, including contamination and the shadowing effect, where increased cell density reduces light availability for photosynthesis. A recent study conducted by researchers at the University of Huelva explores a promising solution to these challenges by investigating the mixotrophic growth of an acid-tolerant microalga, Elliptochloris sp., using CO2-enriched air[1]. Mixotrophy refers to the ability of an organism to derive energy from both photosynthesis (using light) and the consumption of organic carbon sources (like glucose). This dual approach can potentially mitigate the shadowing effect and enhance biomass productivity. The researchers at the University of Huelva grew Elliptochloris sp. cultures in environments with either crude technical glycerin or glucose, while varying the air supply between normal air and air enriched with 2.5% CO2. The study found that CO2 enrichment significantly boosted the growth of Elliptochloris sp. in mixotrophic conditions. Cultures bubbled with CO2-enriched air exhibited higher biomass productivity compared to those with only air. Additionally, CO2-enriched mixotrophy increased the relative abundance of saturated fatty acids, which are crucial for biodiesel production. These findings align with previous studies that have highlighted the benefits of CO2 enrichment for microalgae growth. For instance, earlier research demonstrated that Chlorella vulgaris and Chlorella ellipsoidea achieved their highest biomass growth rates at elevated CO2 concentrations[2]. Furthermore, the study's results indicate that mixotrophy with only air led to an increase in both saturated and unsaturated fatty acids, though the overall biomass productivity was lower compared to CO2-enriched conditions. This suggests that while mixotrophy alone can enhance fatty acid diversity, the addition of CO2 is crucial for maximizing biomass yield. The acid tolerance of Elliptochloris sp. also plays a vital role in its potential for large-scale production. Growing microalgae in acidic conditions can minimize biological contamination, a significant hurdle in outdoor cultivation. Previous research has shown that extremophilic algae, which thrive in harsh conditions like low pH, can be cultivated with reduced risk of contamination and predation, making them suitable candidates for large-scale production[3]. The University of Huelva's study also contributes to the broader understanding of how different cultivation conditions can influence lipid production in microalgae. Earlier studies have demonstrated that mixotrophic cultures generally enhance biomass and lipid production compared to photoautotrophic (light-only) and heterotrophic (organic carbon-only) cultures[4]. However, these studies also noted that increasing light intensity and glucose concentration could boost growth but reduce lipid content. The new findings suggest that a balanced approach, incorporating CO2 enrichment, can optimize both growth and lipid production. In summary, the research conducted by the University of Huelva highlights the potential of mixotrophic growth with CO2-enriched air to enhance the biomass productivity and lipid profile of the acid-tolerant microalga Elliptochloris sp.. This study builds on previous findings that emphasize the benefits of CO2 enrichment and the advantages of extremophilic algae for large-scale cultivation[2][3]. The insights gained from this study could pave the way for more efficient and sustainable microalgae production systems, contributing to the development of renewable biofuels and other valuable bioproducts.

BiotechBiochemPlant Science

References

Main Study

1) Mixotrophic growth of a highly acidic habitat microalga for production of valuable fatty acids

Published 21st May, 2024

https://doi.org/10.1007/s10811-024-03255-5

Related Studies

2) The Influence of Elevated CO2 Concentrations on the Growth of Various Microalgae Strains.

https://doi.org/10.3390/plants12132470

3) Acid Tolerant and Acidophilic Microalgae: An Underexplored World of Biotechnological Opportunities.

https://doi.org/10.3389/fmicb.2022.820907

4) Enhanced growth and lipid production of microalgae under mixotrophic culture condition: effect of light intensity, glucose concentration and fed-batch cultivation.

https://doi.org/10.1016/j.biortech.2012.01.125


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