Toxicological evaluation of <i>Chlamydomonas reinhardtii</i> enriched with protoporphyrin IX

The Chlamydomonas reinhardtii (red) is a strain rich in protoporphyrin IX, which could be used as algal-derived novel sustainable nutritional sources. However, the safety research on C. reinhardtii (red) remains insufficient and further investigation is needed. In order to assess the safety of C. reinhardtii (red) and to expand its use in food applications, a series of toxicological safety evaluations were carried out to observe acute toxicity, subchronic toxicity and genotoxicity of C. reinhardtii (red). The C. reinhardtii (red) was administered to an acute oral toxicity test, mammalian micronucleus test, mouse chromosomal aberration test in Institute of Cancer Research (ICR) mice, and 90-day repeated-dose oral toxicity test in Sprague-Dawley (SD) rats. In the acute oral toxicological test, no mortality or abnormalities were observed in male and female rats, with an median lethal dose(Lethal Dose, 50%) (LD₅₀) exceeding 10.0 g/kg body weight (BW). Similarly, male and female mice exhibited no mortality or abnormalities, with an LD₅₀ surpassing 20.0 g/kg BW. The results of bacterial reverse mutation test, mammalian micronucleus test, and mouse chromosomal aberration test were all negative, suggesting that the C. reinhardtii (red) did not show mutagenicity under the conditions of this experiment. In a 90-day repeated-dose oral toxicity study, the SD rats were orally administered daily doses of 2.0 g/kg BW, 4.0 g/kg BW, and 8.0 g/kg BW without exhibiting any signs or symptoms of toxicity. Therefore, the no observed adverse effect level (NOAEL) of C. reinhardtii (red) was 8.0 g/kg BW/day. This study contributes to information necessary to form a basis for safety for expanding the application range of C. reinhardtii (red) in food. PRACTICAL APPLICATION: The aim of this study was to assess the safety of C. reinhardtii (red) and to expand its use in food applications. The major finding of this study is that the C. reinhardtii (red) did not show acute toxicity, subchronic toxicity and genotoxicity under the conditions of this experiment. This study contributes to information necessary to form a basis for safety for expanding the application range of C. reinhardtii (red) in food.