Biochemical trade-offs and opportunities of commercialized microalgae cultivation under increasing carbon dioxide.

Microalgae's exceptional photosynthetic prowess, CO2 adaptation, and high-value bioproduct accumulation make them prime candidates for microorganism-based biorefineries. However, most microalgae research emphasizes downstream processes and applications rather than fundamental biomass and biochemical balances and kinetic under the influence of greenhouse gases such as CO2. Therefore, three distinctly different microalgae species were cultivated under 0% to 20% CO2 treatments to examine their biochemical responses, biomass production and metabolite accumulations. Using a machine learning approach, it was found that Chlorella sorokiniana showed a positive relationship between biomass and chl a, chl b, carotenoids, and carbohydrates under increasing CO2 treatments, while Chlamydomonas angulosa too displayed positive relationships between biomass and all studied biochemical contents, with minimal trade-offs. Meanwhile, Nostoc sp. exhibited a negative correlation between biomass and lipid contents under increasing CO2 treatment. The study showed the potential of Chlorella, Chlamydomonas and Nostoc for commercialization in biorefineries and carbon capture systems where their trade-offs were identified for different CO2 treatments and could be prioritized based on commercial objectives. This study highlighted the importance of understanding trade-offs between biomass production and biochemical yields for informed decision-making in microalgae cultivation, in the direction of mass carbon capture for climate change mitigation.

Distinctive correlations between cell concentration and cell size to microalgae biomass under increasing carbon dioxide.

Carbon capture and storage (CCS) via microalgae cultivations is getting renewed interest as climate change mitigation effort, owing to its excellent photosynthetic and CO2 fixation capability. Microalgae growth is monitored based on their biomass, cell concentrations and cell sizes. The key parametric relationships on microalgae growth under CO2 are absent in previous studies and this inadequacy hampers the design and scale-up of microalgae-based CCS. In this study, three representative microalgae species, Chlorella, Nostoc and Chlamydomonas, were investigated for establishing key correlations of cell concentrations and sizes towards their biomass fluctuations under CO2 influences of 0% to 20% volume ratios (v/v). This revealed that Chlorella and Chlamydomonas cell concentrations significantly contributed towards increasing biomass concentration under CO2 elevations. Chlorella and Nostoc cell sizes were enhanced at 20% (v/v). These findings provided new perspectives on growth responses under increasing CO2 treatment, opening new avenues on CCS schemes engineering designs and biochemical production.