Astaxanthin has been reported to improve the growth rate and survival of larvae in aquaculture, improve the reproductive performance and egg quality of aquatic animals, and enhance disease resistance and immune response in farmed fishes against infectious diseases. The natural astaxanthin is in great demand in the market in recent years.   

Mixotrophic cultivation of Haematococcus is efficient to increase astaxanthin productivity. However, application of this technique in open raceway ponds, a main bioreactor for industrial Haematococcus astaxanthin production, is restricted because of bacterial contamination.  

The research group led by LI Yeguang from Wuhan Botanical Garden successfully carried out mixotrophic cultivation of Haematococcus in an outdoor raceway pond.    

The Haematococcus cells grew on light firstly, and then acetate/acetic acid was added to the cultures under nitrogen-depleted conditions. Under such conditions, Haematococcus cells grew on intracellular nitrogen pool, while bacterial reproduction was limited. The average astaxanthin productivity reached 140 mg m^-2day^-1, which increased more than 20% of the simple phototrophic cultivation. 

This method potentially can be used for mass cultivation of astaxanthin-rich Haematococcus mixotrophically in open bioreactors. 

Results have been published in Aquaculture International entitled “Enhancing the production of astaxanthin by mixotrophic cultivation ofHaematococcus pluvialis in open raceway ponds”. It was supported by the Science and Technology Service Network Initiative of the Chinese Academy of Sciences. 

Changes of culture suspension appearance in raceway pond (Image by WBG)