Dynamic changes of inorganic nitrogen and astaxanthin accumulation inHaematococcus pluvialis

Abstract

This study on dynamic changes of culture color, astaxanthin and chlorophylls, inorganic N including N−NO ⁻₃ , N−NO ⁻₂ and N−NH ⁺₄ in batch culture ofHaematococcus pluvialis exposed to different additive nitrate concentration showed (1) ast/chl ratio was over 0.8 for brown and red algae, but was usually less than 0.5 for green and yellow algae; (2) N−NO ⁻₃ , in general, was unstable and decreased, except for a small unexpected increase in nitrate enriched treatment groups; (3) measurable amounts of N−NO ⁻₂ , and N−NH ⁺₄ were observed respectively with three change modes although no external nitrite and ammonia were added into the culture; (4) a non-linear correlation between ast/chl ratio (or color) changes and the levels of N−NO ⁻₃ , N−NO ⁻₂ , N−NH ⁺₄ inH. pluvialis culture; (5) up and down variation of the ast/chl ratio occurred simultaneously with a perceptible color change from yellow to brown (or red) when N−NO ⁻₃ , N−NO ⁻₂ and N−NH ⁺₄ fluctuated around 30, 5, 5, μmol/L respectively; (6) existence of three dynamic modes of N−NO ⁻₃ , N−NO ⁻₂ and N−NH ⁺₄ changes, obviously associated with initial external nitrate; (7) the key level of total inorganic N concentration regulating the above physiological changes during indoor cultivation was about 50 μmol/L; and (8) 0.5–10 mmol/L of nitrate was theoretically conducive to cell growth in batch culture.