The related research results were published in Aquaculture.

H. pluvialis is a unicellular green alga that has been widely recognized for its ability to accumulate astaxanthin in large quantities and is currently also the best established biological source of natural astaxanthin in nature. studies show that the use of appropriate combinations of red and white light can promote the growth of H. pluvialis and improve astaxanthin production, but the processes and mechanisms in which red light plays a role are not well understood.

In this study, researchers worked on a new method to promote growth of Haematococcus pluvialis.

After switching the illumination culture mode from white to red light in the late logarithmic phase of growth, researchers found that autotrophic growth of H. pluvialis was improved.

They also confirmed that red light could promot enhanced photosynthesis and increase CO₂ fixation rates by regulating the activity of carbonic anhydrases and maintaining the pH of the medium stable between 8 and 9.

Their further study revealed the related mechanism. The red light regulated the transcription factors of carbonic anhydrase gene expression possibly through the phytochrome mediated COP1-SPA1 complex pathway, which upregulated the expression of carbonic anhydrase genes CAH1 and CAH3, and then affected the activity of carbonic anhydrase.

"Our work can provide guidance for more efficient use of light during microalgal culture to achieve photoautotrophy and for potential practical applications in carbon neutralization," said LI Lamei, first author of the paper.

This study was supported by the National Natural Science Foundation of China.

Effect of red light on the activity of intracellular carbonic anhydrase and CO2 fixation efficiency after different time.
A: Activity of carbonic anhydrase in H. pluvialis cells as a function of incubation time with red light; B: Changes in CO2 fixation efficiency of algal cells after conversion from white to red light incubation. (Image by LI Lamei)

Schematic diagram of the mechanism by which red light promotes autotrophic growth of algal cells. (Image by LI Lamei)

Published on Mar. 12