Complementary limiting factors of astaxanthin synthesis during photoautotrophic induction of Haematococcus pluvialis: C/N ratio and light intensity.

We investigated the effect of carbon/nitrogen (C/N) ratio on astaxanthin synthesis in Haematococcus pluvialis during photoautotrophic induction by continuous input of both CO(2)-air mixture and intense light. When H. pluvialis was induced by constant irradiance induction at 200 micromol photon m(-2) s(-1), there was a positive correlation with astaxanthin content and C/N ratio, which was similar to the case for heterotrophic induction. Lower C/N ratios did not retard Haematococcus encystment, but did increase culture biomass, resulting in a decrease in astaxanthin production because of light limitation. However, induction using variable irradiance showed that reduction of astaxanthin production at low C/N ratios was successfully overcome by simply increasing the light intensity from 200 to 300 micromol photon m(-2) s(-1) to overcome the light limitation. This resulted in a greatly enhanced astaxanthin synthesis in proportion to cell density in cultures with low C/N ratios. Our results indicate that light intensity is more critical than C/N ratio in astaxanthin production by H. pluvialis during photoautotrophic induction.

Comparison of heterotrophic and photoautotrophic induction on astaxanthin production by Haematococcus pluvialis.

During light induction for astaxanthin formation in Haematococcus pluvialis, we substituted photoautotrophic induction for heterotrophic induction using acetate, both to prevent contamination by heterotrophs due to addition of organic carbon and to enhance carbon assimilation in the induced cells. Strong photoautotrophic induction was performed by N-deprivation of photoautotrophically grown Haematococcus cells followed by supplementation with bicarbonate (HCO(3)(-)) or CO(2). Bicarbonate-induced cells contained more astaxanthin than acetate-induced cells, and even further enhancement of astaxanthin accumulation was achieved by continuous CO(2) supply. The maximum astaxanthin content (77.2 mg g(-1) biomass, 3.4-fold higher than with heterotrophic induction) was obtained under conditions of 5% CO(2), yielding astaxanthin concentration and productivity of 175.7 mg l(-1) and 6.25 mg l(-1) day(-1), respectively. The results indicate that photoautotrophic induction is more effective than heterotrophic induction for astaxanthin synthesis in H. pluvialis.

Shikonin production by extractive cultivation in transformed-suspension and hairy root cultures of Lithospermum erythrorhizon.

Effects of in situ extraction, fungal elicitation, a permeabilizing agent, and the oxygen transfer rate on shikonin production in transformed suspension and hairy root cultures of Lithospermum erythrorhizon were studied. Shikonin production with in situ extraction in transformed cell and hairy root cultures by n-hexadecane was 7.6 and 3 times higher than those of the control culture. Shikonin production of transformed L. erythrohizon increased with the enhanced gas exchange, and in situ extraction also increased sucrose consumption and shikonin production. The optimal volume of n-hexadecane in the hairy root culture was similar to that in the transformed cell cultures. In situ extraction at an earlier stage significantly enhanced shikonin production both in transformed cell and hairy root cultures. Dimethylsulfoxide used as a permeabilizing agent was harmful to cell growth and shikonin production, and permeabilizing was unnecessary when in situ extraction was applied. This occurred because with the solvent addition, most shikonin was spontaneously released from the cells and was dissolved in the solvent layer. The combined addition of n-hexadecane of the extract of the fungus Penicillium as an elicitor seemed to result in a higher production of shikonin both in cell suspensions and transformed root cultures. However, an increase of shikonin induction by fungal elicitation in a hairy root culture was not significant in comparison with that of normal cell cultures.