For the past decade, microalgae cultivation technique in large scale has been improved greatly. Area productivity and volumetric growth rate has been elevated for multiple folds and cost for cultivation has been driven down significantly.
One criteria for commercial scale microalgae cultivation is use of large raceway ponds and high volume water. This is inevitable for all the algae product producer, except one with sophisticated tubing matrix system. However, there are many issues with the large raceway ponds.
- Large raceway ponds are very susceptible to biological predation and chemical contamination. Predators such as vorticella, rotifer can graze up to thousands of algae cells.
- Due to use of carbon dioxide to feed the microalgae during autotrophic stage, the media gradually turns acid which eventually become no more viable for algae cells.
Figure 1. A high throughput experiment conducted by our team to find the optimal combinatory conditions that support algae growth and productivity
A combinatorial use of nitrogen source for nutrient stoichiometry is developed to solve the two issues and achieve a more efficient uptake of nitrogen for microalgae growth.
- Combinatorial nitrogen sources could provide a pH-balanced media for microalgae with the continuous addition of CO2.
- Use of combinatorial nitrogen sources essentially reduce the use of nitrate in the media, which limit the growth of foreign microorganism, in order to alleviate the risk of biological predation.
- Combinatorial nitrogen sources render better cell growth and volumetric productivity than single nitrogen formula.
Figure 2. Cells were treated with different singular/combinatory nitrogen sources plus the nitrogen-free medium. In the graph, “single” means singular nitrogen source, “double and triple” means two and three combinatory nitrogen source respectively. From the result, it shows combinatory works better than singular nitrogen sources.