Enhanced Production of Astaxanthin without Decrease of DHA Content in Aurantiochytrium limacinum by Overexpressing Multifunctional Carotenoid Synthase Gene

Transcriptional responses of Aurantiochytrium limacinum under light conditions

“…A. limacinum cells were harvested after culturing for 24, 48 and 72 h under both dark and light conditions. Carotenoid extraction from A. limacinum cells was performed in triplicate using a combination of protease/glass beads and chloroform/methanol procedures with a modified incubation time of 1 h (Kubo et al, 2021). Aliquots of the resultant extracts were quantified using high‐performance liquid chromatography MD‐2018 (JASCO), with a PU‐2089 pump (JASCO) and CrestPak C18T‐5 column (JASCO).…”

“…After culturing for 3 days, 300 μl of the cultures (optical density [OD] 600 = 4.0) was inoculated into fresh medium (total volume 30 ml). The Aurantiochytrium cells were then cultured under dark or continuous light conditions (light intensity: 0 or 50 μmol photons m −2 s −1 ) according to a previous study (Kubo et al, 2021). This experiment was carried out in triplicate.…”

“…Temporal changes in the transcript abundance of carotenoid synthesis-related genes, CarS (Kubo et al, 2021) and CrtZ were investigated in triplicate by quantitative reverse-transcription polymerase chain reaction (RT-qPCR). We designed a novel primer set for the CrtZ gene (CrtZ-F 5′-TCCACTCCAGCCACCATAACC-3′ and CrtZ-R 5′-TGCAAAGAATACCACAAACCAGTCA-3′).…”

“…Carotenoid measurements were conducted using the mobile phase solution A (acetonitrile:methanol:distilled water = 75:15:10) and B (ethyl acetate:methanol = 30:70), each containing 0.1% ammonium acetate, under the same conditions as previously described (Kubo et al, 2021). The obtained results were examined by Student's t test.…”

“…In particular, astaxanthin is a strong antioxidant that plays a role in promoting immune responses, and prevents photooxidation, inflammation and aging (Guerin et al, 2003; Yamashita, 2015). Strikingly, A. limacinum is known to produce a higher amount of astaxanthin under light conditions despite being a non‐photosynthetic micro‐organism as well as other thraustochytrids (Chatdumrong et al, 2007; Kubo et al, 2021; Yamaoka et al, 2004). As the current process of astaxanthin production in the microalga Haematococcus lacustris is extremely complex, due to its cyst formation and low biomass (Choi et al, 2019; Fábregas et al, 2000), A. limacinum is regarded as a promising alternative resource for commercial astaxanthin production.…”