The combination of uridine and nitrogen-deprivation promotes the efficient formation of astaxanthin-rich motile cells in Haematococcus pluvialis.

Astaxanthin accumulation in Haematococcus pluvialis typically occurs alongside the formation of secondary cell wall (SCW), hindering astaxanthin extraction and bio-accessibility. A potential solution lies in cultivating astaxanthin-rich motile cells lacking SCW. This study explored the influence and underlying mechanism of nitrogen-deprivation (ND) on SCW formation and established a connection between pyrimidine metabolism and SCW development. Then, various pyrimidine and ND combinations were examined to cultivate astaxanthin-rich motile cells. The results indicated that, compared to the nitrogen-replete group, the combination of uridine and ND increased the proportion of motile cells by 25-33 times, achieving 95 %, and enhanced astaxanthin yield by 26.52 %. Moreover, the efficiency of astaxanthin extraction from intact, wet motile cells was 91 % - 95 %, which was 5.6-9.0 times that from non-motile cells. This study not only presents a promising method for producing astaxanthin-rich motile cells in H. pluvialis but also provides insights into the relationship between pyrimidine metabolism and SCW development.