Enhanced astaxanthin extraction efficiency from Haematococcus pluvialis via the cyst germination in outdoor culture systems

Haematococcus pluvialis is the richest source of natural astaxanthin (3S, 3′S), but the rigid cell wall of mature red cyst (aplanospore) complicates the efficient extraction of astaxanthin from the strain. Herein, the cyst germination method was developed by using nitrate and light for practical application for an efficient astaxanthin extraction from Haematococcus cells cultured in outdoor condition where flue gas, solar radiation and photobioreactor were used. Notably, autotrophic germination rate was easily regulated by light intensity. Under conditions of low germination rate, total astaxanthin concentration was highly maintained and astaxanthin extraction efficiency was rapidly enhanced during autotrophic germination. As a result, under homogenization (30 s), the extracted astaxanthin concentration in the cells treated with 1 mM KNO₃-150 μE/m²/s was highly increased by 58% compared to the cells treated without germination. Our technical solution will definitely improve an astaxanthin extraction titer with the practical application in outdoor Haematococcus culture system.