The Role of Photo-Cycles in the Modulation of Growth and Biochemical Profile of Microalgae: Part I-Food Interest Compounds

\ The objective of this work was to evaluate the effect of different photo-cycles on the growth and biochemical profile of Scenedesmus obliquus CPCC05, focusing on food interest compounds. The photo-cycle conditions were separated into three groups: long-term photo-cycles (24:0, 22:2, 20:4, 18:6, 12:12, and 10:14 (h:h)), frequency photo-cycles (2, 4, 8, 12, 24, and 48 times per day (t/d)), and short photo-cycles (0.91:0.09, 0.83:0.17, 0.75:0.25, and 0.50:0.50 (s:s)) of light:dark, respectively. The results showed these microalgae can store enough energy to support cell growth for continuous periods of up to 2 h in the dark, without affecting the productivity of the process. This 2 h, when divided into 2 cycles per day (2 t/d), showed the best growth condition (3700 mg L-1), generation time (14.40 h), and maximum biomass productivity (21.43 mg L h(-1)). This photo-cycle of 2 t/d was also the best condition for the production of total sterols. However, the values of polyunsaturated fatty acids, lipid content, and amino acids obtained higher yields in the short photo-cycle of 0.75:0.25. Thus, the modulation of light cycles becomes an important tool for boosting and directing the production of target molecules in phototrophic cultures of microalgae.

Automated summary

This study evaluated the effect of different photo-cycles on the growth and biochemical profile of Scenedesmus obliquus. The results showed that a photo-cycle of 2 times per day yielded the best growth, generation time, and biomass productivity. However, a short photo-cycle of 0.75:0.25 resulted in higher yields of polyunsaturated fatty acids, lipid content, and amino acids.