Abstract

Porphyridium purpureum is a red microalga that contains phycoerythrin (R-PE), exopolysaccharides (EPS) and polyunsaturated fatty acids (PUFAs): linoleic acid (LA), eicosapentaenoic acid (EPA), and arachidonic acid (AA). The optimization of culture conditions remains a major challenge for enhancing biomass production on a large scale. In this study, a random mutagenesis-selection approach to enhance the physiological and biochemical traits of P. purpureum was used. UV-C radiation (254 nm) served as the mutagenic agent, while dim light and the fatty acid biosynthesis inhibitor Cerulenin, were employed as selection agents. Four mutant strains (A-4, B-3, B-7, and B-11) were selected and evaluated at the laboratory scale (1 L). According to their growth and biochemical attributes, strains B-7 and B-11 were selected and used for outdoor trials in 350 L tubular photobioreactor. The strains B-7 and B-3 in 350-L trials achieved similar percentages of total polyunsaturated fatty acids (ranging from 60 to 64%) compared to the wild-type strain. However, only the B-7 strain showed an increase in total lipid accumulation, rising from 5.9% to 6.5% relative to the wild type; additionally, LA and ARA increased by 49.5% and 52.3.7%, respectively, while EPA decreased by 56.7% compared to the wild type. Concerning phycoerythrin, improvements were observed only in strain B-7 (from 14.4 to 20.6 mg g-1 dry biomass). The biomass production per culture volume increased by approximately 53.2% for B-7 and 35% for B-3, respectively, relative to the wild type, indicating that notable properties of the mutant strains could be observed at a large culture scale. Regarding the potential use of these strains in nutraceutical applications, cytotoxicity tests of strains B-3 and B-7 showed no harmful effects on healthy human cell lines. Furthermore, both strains demonstrated some antitumoral activity against colon cancer HCT-116 cells. This study demonstrated that random mutagenesis-selection is a valuable approach for selecting new P. purpureun strains for biotechnological applications.