Study On The Photoinduction Of Haematococcus Pluvialis For Highly-efficient Astaxanthin Production

Natural astaxanthin is a substance with high biological activity and extensive applications. Compared with other organisms, unicellular green algae Haematococcus pluvialis is recognized as the best biological source for natural astaxanthin In order to meet the market demands, the establishment of an efficient way to culture Haematococcus pluvialis and to induce it for accumulating astaxanthin has been a research hotspot. Currently, the successful strategy for the commercial production systems was established base on the two-step culture. The first stage, green vegetative growth phase, is done to obtain a large quantity of green vegetative cells under the favorable culture condition. And the second stage, reddish inductive production phase, is the induction of cells to accumulate astaxanthin with the transition of green vegetative cells to reddish cyst cells in various stress conditions. Therefore, the effect of photoindution affects the cell growth and astaxanthin accumulation directly, and determines the astaxanthin productivity.In this study, the main goal of this project was to increase the yield of astaxanthin from the following four aspect:,the determination of basic condition of H. pluvialis induction, the optimization of induction medium, the effect of induced wastewater on recycle induction of H. pluvialis and the development of attached induction. The main results are as follows:(1) The basic conditions for outdoor induction were determined:the initial cell concentration should be in the range of0.3g L-1to0.5g L-1and the ventilation volumn was0.5(v.v.m) during the daytime and no mixing at night. Then, the optimal temperature of induction was in the range of23to28℃and the optimal pH of induction was in the range of7to8.(2) The effects of different light sources were difference and the white light was the best light source.(3) The effect of different carbon sources on the cell growth and asataxanthin accumulation of H. pluvialis is different. The effect of inorgan carbon sources on the cell induction is better than the effect of organ carbon sources. And CO2is the best carbon source for cell growth and astaxanthin accumulation of H. pluvialis. Besides, there is no effect of the Fe2+, organophosphorus, piv, vb on the cell induced of H. pluvialis.(4) For the problem of wastewater treatment in the astaxathin production, results in the experiment of water recycling were confirmed: after induced, the wastewater with preliminarily treatment can be recycling for the next induction at least3times. With the appropriately medium supplemented, the effect of recycle induction was similar with that with acyclic water. These would be greatly improve water utilization and reduce the costs of wastewater treatment.(5) Meanwhile, the attached induction of H. pluvialis has been developed. The optimal initial cell mount was in the range of10to20g m-2and the best temperature was25℃. And the attached induction of H. pluvialis can take place in poor light intensity and the less water condition. Besides, the protozoan contamination of attached induction was less. Therefore, it has many merits, such as power cost-effective, low water consumption, and small risk of contamination.This study has laid a good foundation for the industrialization of Haematococcus pluvialis induction with a high rapidly accumulation of astaxanthin.