Exogenous sodium fumarate enhances astaxanthin accumulation in Haematococcus pluvialis by enhancing the respiratory metabolic pathway.

Improvement of astaxanthin yield is a continuing objective in Haematococcus pluvialis cultivation. In this study, a new strategy combining exogenous sodium fumarate (SF) with nitrogen deficiency was demonstrated to promote astaxanthin accumulation in H. pluvialis. SF significantly accelerated astaxanthin synthesis over cell growth. Notably, under nitrogen deficiency, 10 mM SF increased the cellular astaxanthin content by 1.75-fold and 1.47-fold on day 7 and 12, respectively. Further studies indicated that SF increased the level of respiratory metabolites in the Embden-Meyerhof-Parnas pathway, tricarboxylic acid cycle and pentose phosphate pathway. An enhanced substrate pool due to the acceleration of respiratory metabolic pathways directly induced astaxanthin synthesis. Meanwhile, the accumulation of C18:1, C18:2 and C18:3 fatty acids enhanced astaxanthin synthesis indirectly by promoting the process of esterification. This study not only helps to elucidate the role of respiratory metabolic pathways in astaxanthin synthesis but also provides a new effective technique to improve astaxanthin production.