Influence Of UV-B Irradiation On The Growth And Carotenoid Accumulation Of Haematococcus Pluvialis

Haematococcus pluvialis is a kind of the fresh-water green unicellular alga. Under stress conditions, Haematococcus pluvialis can accumulate a large amount of secondary carotenoids, among which over 80% are astaxanthin esters. Astaxanthin has many important biological functions, and is widely used as food additives, or as feed additives of aquatic and poultry. Because of its higher antioxidant activity, astaxanthin is widely used in medicine, cosmetics and nutraceuticals, etc. In this paper, we studied the growth laws of Haematococcus pluvialis under various conditions and especially, the effect of UV-B radiation on the growth, the accumulation of carotenoids and the changes in antioxidant enzymes activities of Haematococcus pluvialis. The main results are as follows:1. The optimization of conditions of the cultivation Haematococcus pluvialis. Influence of culture medium, temperature and light intensity was studied on the growth of Haematococcus pluvialis. The results showed that the suitable medium for vegetative growth of Haematococcus pluvialis is HGZ, and cell number reached the maxium value in 9-10 d (90×104 cells·mL-1). The suitable temperature and light intensity was 20℃and 4000 Lux, respectively.2. The effect of UV-B radiation on the growth of Haematococcus pluvialis. Haematococcus pluvialis was cultured under UV-B condition for 16 days. The dry weight of the alga raised slowly within 8 d and declined after 9 d. The content of Chla of the alga increased within 9 d and declined after 10 d. On the 16 d, the value of chlorophyll fluorescence (Fv/Fm) and the rate of oxygen release kept nearly constant in PAR, the Fv/Fm and the rate of oxygen release declined with the UV-B intensities. The results showed that the growth of the alga was obviously inhibited by UV-B radiation.3. The astaxanthin synthesis in Haematococcus pluvialis under UV-B radiation. The activities of SOD, CAT and AsA-POD in the alga were increased within 2-3 d after UV-B radiation, and then declined. The UV-B radiation also improved the contents of carotenoids which can absorb UV-B. The contents of carotenoids were raised to 630%, 459%,370%, as compared with the control 10 days after UV-B radiation. With the increase of UV-B intensities, the color of cell turned into reddish-brown with red spots in central section, the big vacuole was vanished and cytoplasm was filled with carotenoid grains of middle electron density.Our results show that the carotenoid contents were increased under UV-B radiation, our finding is of great importance to the large-scale prepare astaxanthin in Haematococcus Pluvialis.