Microalgae Haematococcus pluvialis is the richest natural source of astaxanthin and has become the primary source for astaxanthin production so far. However, its thick resistant cell wall probably represents the biggest barrier for target compound extraction. Therefore, high energy-consuming and cost-intensive downstream processes such as cell disruption and drying are required to improve extraction efficiency. In the present study, an approach to selectively extract astaxanthin and lipid using aqueous ethanol from algal biomass of H. pluvialis with moisture content of 80%, following a pre-process of acidic hydrolysis cell wall disruption, was proposed. Experiments for parameters optimization and for investigation of mechanism of this approach to improve extraction performance were also carried out. The results showed that polar fractions (mainly chlorophyll and polar lipids) and neutral fractions (mainly carotenoids and triglyceride) were selectively extracted in different extraction cycles, thus fraction extraction was achieved as consequence of the change of ethanol concentration in different extraction cycles. Solvent or solvent mixtures with moderate polarity act out better selectivity and efficiency for carotenoids (mainly astaxanthin), i.e. extraction using ethanol/ethyl acetate mixture gave a total yield of carotenoids reaching 25.31 mg/g of dry weight, a recovery rate of 69.35% and a high content ratio of carotenoids to chlorophyll of 10.6. With assistant of acidic cell-wall disruption, the extraction efficiency of astaxanthin and lipid were significantly improved, in particular, the total yield of lipid reached 418 mg/g dry weight and the recovery rate of lipid reached 97% under the optimal acidic hydrolysis cell-wall disruption conditions of HCl 1 mol/L, temperature of 60℃ and time 60 min. The extracted astaxanthin and fatty acid maintained their chemical stability during extraction process. Therefore, this approach for selectivity extraction astaxanthin and triglyceride from wet algal biomass was demonstrated, and could be an alternative with multiple benefits including extraction efficiency improvement and cost reduction, for astaxanthin production from algal biomass of H. pluvialis.
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