| Abstract: | In this study, carotenoid contents of Haematococcus pluvialis during outdoor high light cultivation were measured, moreover, changes of astaxanthin geometrical isomers and biotic factors which may affect isomerization were investigated. During the incubation, contents of both astaxanthin and its precursors (zeaxanthin and canthaxanthin) increased over time, whereas the relative content of lutein decreased. Contents of all astaxanthin isomers increased, while the proportion of different astaxanthin geometrical isomers fluctuated during the incubation. All‐trans‐astaxanthin of total astaxanthin (T/A) was higher during the astaxanthin accumulation phase than that in the cell transformation phase, which was in contrast to results of 13‐cis‐astaxanthin of total astaxanthin (13C/A) and 9‐cis‐astaxanthin of total astaxanthin (9C/A). Farnesyl diphosphate synthase (trans (2E,6E)‐FPPS, EC2.5.1.10) and geranylgeranyl diphosphate synthase (GGPS, EC2.5.1.29), the key proteins involved in geometrical isomerization, decreased during the astaxanthin accumulation phase. Moreover, the presence of cis (2Z,6E)‐FPPS was firstly confirmed in H. pluvialis by HPLC‐MS/MS shotgun method. The results indicated the biotic factor (trans‐FPPS, cis‐FPPS and GGPS) may play an important role in astaxanthin geometrical isomerization of H. pluvialis, but not a crucial role. This study would help in optimizing the regulation of astaxanthin geometrical isomers in H. pluvialis, with great significance in theory and production. |
