Effects of light intensity on the production of phycoerythrin and polyunsaturated fatty acid by microalga Rhodomonas salina

Phycoerythrin (PE) is a phycobilipmtein with great potential in food, pharmaceuticals, and cosmetics applications. This work sought to investigate the effects of lighting conditions on the PE synthesis by the alga Rhodomonas salina. It was found that the effects of light intensity on the cell growth and PE synthesis highly depend on the cell density, and ultimately, the number of photons received per unit of cells. No obvious light limitation or inhibition to cell growth was observed when each cell received the photons within the range of 2.4-28 x 10(-9) mu mol.s(-1). Under low light intensity, R. salina increased the PE synthesis in order to capture more photons to compensate light deficiency. A strategy of stepwise increasing light intensity was developed to capture the rapid cell growth and high PE synthesis. The PE titer with this method reached 32 mg L-1, similar to 20% higher than that obtained at a fixed light intensity of 250 mu mol photon flux m(-2) s(-1) (mu mol.m(-2).s(-)(1)). In addition to PE synthesis, R. salina also produces an appreciable amount of omega-3 polyunsaturated fatty acids (PUFAs) with stearidonic acid (SDA, C18:4) in particular. Collectively, this work demonstrates that light intensity plays an important role in the culture of R. salina for simultaneous production of PE and PUFAs.

Automated summary

This study reveals the significant impact of lighting conditions on cell growth and PE synthesis in Rhodomonas salina, with increasing light intensity leading to higher production of PE and PUFAs.