Abstract:Haematococcus pluvialis is a microalga, and this species is economically important since it is a rich source of natural astaxanthin, which is considered a “super anti-oxidant.” The study was conducted using H. pluvialis LUGU filtrated from Lugu Lake in Yunnan Province, China. Studies have shown that under stress, the exogenous addition of appropriate concentration of butylated hydroxytoluene (BHT) can effectively promote the accumulation of astaxanthin and increase the content of lipids in the algal cells. The effects of BHT on several traits were investigated under stress conditions (high illumination and nitrogen deficiency), including the impact on growth of algae; the accumulation of astaxanthin; the synthesis of lipids; the composition of fatty acids, carbohydrates and protein; the expression level of the key enzyme gene of astaxanthin; and fatty acid biosynthesis. In this study, the different concentrations of BHT (0, 1, 2, and 3 mg/L) were achieved through single factor experiments in algal cell culture medium. Results from these experiments showed that BHT treatment does not effectively promote the algae growth, but it does affect the accumulation of astaxanthin in algae cells. There was a significant dose effect depending on the BHT treatment applied to H. pluvialis. After examining BHT additions of different concentrations, astaxanthin accumulation was determined to be the highest after the 2 mg/L BHT treatment, and it was significantly higher than that resulting from other treatments or the control group (P<0.05). Moreover, astaxanthin accumulation was 1.87 times higher than that in the control group, reaching 31.66 mg/g. The lipid content of the 2 mg/L BHT treatment was 45.56%, which was also higher than that in the control (39.06%). Under these conditions, the expression levels of the key enzyme genes of astaxanthin synthesis, dxs and bkt, were 5.19 folds and 2.04 folds, respectively, as those of the control, and the expression levels of the key enzyme genes of fatty acid synthesis, kas and acp, were significantly higher than those of the control (P<0.05), being 4.56 folds and 3.02 folds, respectively, as those of the control. Contrastingly, the carbohydrate and protein contents decreased compared to those of the control group. Overall, our results also show that BHT can increase accumulation of astaxanthin and increase the content of lipids in the algal cells when administered at an appropriate dose.
