Exploring the impacts of photoperiod strategies on biomass and PUFA production in the polar marine microalga Chlamydomonas sp. RCC2488 (malina)

Chlamydomonas sp. RCC2488 ( malina ) is a polar microalga that inhabits environments characterized by extreme and fluctuating conditions, including prolonged light:dark periods. This study evaluated the growth and PUFA production of Chlamydomonas ‘malina’ under different photoperiods: 24:0 (continuous light, control), 16:8, 14:10 and 12:12 (h:h, light:dark). Growth was affected even by relatively short dark periods (16:8 h:h), as cells divided less under light:dark photoperiods than under continuous light, resulting in lower cell densities despite similar biomass dry cell weight at the end of cultivation. Lipid accumulation increased under 16:8, 14:10 and 12:12 photoperiods, and the lipid fraction consisted predominantly of membrane-associated polar lipids, reaching a PUFA productivity of 22.9 mg fatty acids (FA) L⁻ 1 day⁻ 1 . Protein and photopigment contents decreased as the duration of darkness increased, whereas lipid content showed the opposite trend. The 12:12 photoperiod promoted the highest lipid accumulation and PUFA productivity, but arrested cell doubling and protein synthesis. These results demonstrate that photoperiod manipulation effectively modulates metabolic partitioning in Chlamydomonas ‘malina’ , redirecting carbon toward PUFA-rich lipids and highlighting photoperiod control as a practical tool for tailoring lipid composition in polar microalgal cultures. Compared with continuous light (24:0), light:dark photoperiods, particularly 12:12 photoperiod, promoted greater accumulation of ALA and DHA, highlighting the influence of dark periods on PUFA biosynthesis and lipid remodeling in this polar microalga.