Résumé
The aim of this study was to promote fucoxanthin accumulation in Phaeodactylum tricornutum by photo-fermentation through optimizing the mode of multiple nitrogen supplementation and blue light enhancement. The results showed that the mixed nitrogen source (tryptone: urea=1:1, N mol/N mol; total nitrogen concentration at 0.02 mol/L) added to the culture system by six times was the best mode in shake flasks. Two-phase culture with light adjustment was then carried out in 5 L photo-fermenter with an enhanced blue light (R: G: B=67.1:16.7:16.3) in the second phase, leading to improved cell density (1.12×108 cells/mL), biomass productivity (330 mg/(d·L)), fucoxanthin content (19.62 mg/g), titer (69.71 mg/L) and productivity (6.97 mg/(d·L)). Compared with one-phase culture under red/blue (R: G: B=70.9:18.3:10.9) light and six-times nitrogen supplementation, the fucoxanthin content was significantly increased by 7.68% (P < 0.05) but the productivity did not change significantly (P > 0.05). Compared with one-phase culture under red/blue (R: G: B=70.9:18.3:10.9) light and one-time nitrogen supplementation, the content and productivity of fucoxanthin were significantly increased by 45.98% and 48.30% (P < 0.05), respectively. This study developed a two-phase culture mode with multiple nitrogen supplementation and blue light enhancement, which effectively promoted the accumulation of fucoxanthin and improved the efficiency of nitrogen source utilization, thus providing a new approach for fucoxanthin accumulation in P. tricornutum by photo-fermentation.
Sujets)
Azote , Lumière , Xanthophylles , Diatomées , Compléments alimentairesRésumé
The aim of this study was to develop a technical system for high-efficient production of fucoxanthin by photo-fermentation of Phaeodactylum tricornutum. In a 5 L photo-fermentation tank, the effects of initial light intensity, nitrogen source and concentration as well as light quality on biomass concentration and fucoxanthin accumulation in P. tricornutum were investigated systematically under mixotrophic condition. The results showed that the biomass concentration, fucoxanthin content and productivity reached the highest level of 3.80 g/L, 13.44 mg/g and 4.70 mg/(L·d) under the optimal conditions of initial light intensity of 100 μmol/(m2·s), 0.02 mol TN/L of tryptone: urea (1:1, N mol/N mol) as mixed nitrogen source, and a mixed red/blue (R: B=6:1) light, 1.41, 1.33 and 2.05-fold higher than that before optimization, respectively. This study developed a key technology for enhancing the production of fucoxanthin by photo-fermentation of P. tricornutum, facilitating the development of marine natural products.
Sujets)
Fermentation , Xanthophylles , Lumière , Diatomées , AzoteRésumé
Aims: To determine effects of aromatic hydrocarbons and marine sediments from Niger Delta on the growth of microalga Phaeodactylum tricornutum. Study Design: Fifteen treatments and the control were designed in triplicates in which long cells containing 25 mL of the algae-toxicant dilutions were supplemented with 0.0 mg /L, 1.0 mg /L, 1.8 mg /L, 3.2 mg /L, 5.6 mg /L, and 18.0 mg /L of xylene, anthracene and pyrene each; three sediments and potassium dichromate incubated for 3 days at 20 ± 2°C. The fifteen treatments and control (K2Cr2O7) designated as C0, C1, C2, C3, C4 and C5 were used to determine their median effective concentration (ErC50) on the growth of microalga Phaeodactylum tricornutum. Place and Duration of Study: Department of Microbiology, Chukwuemeka Odumegwu Ojukwu University, Uli Nigeria between February, 2018 and July, 2018. Methodology: A laboratory scale study was carried on the sediment samples from the three studied areas using physiochemical analysis and marine microalga toxicity test. Results: The findings revealed that the three sampling sites contain higher quantities of aromatic hydrocarbons, heavy metals and other physio-chemical parameters in the sediment samples than water samples. The K2Cr2O7had the highest ErC50 value of 08.07 ± 0.03 mg /L with CV and r2 values of 68.61% and 0.99 while pyrene in Nembe sediment had the least ErC50 value of 04.63 ± 0.01 mg /L with CV and r2 values of 78.27% and 0.98 with very strong significant positive linear relationship between algal number and sample concentrations (P = .05). Conclusion: Thus, the toxicity results (> 1 mg /L <EC50 ≤ 10 mg /L) in this study are in line with other toxicity values for this type of toxicants, and are therefore considered to be scientifically relevant in ecotoxicological risk assessment of Niger Delta, Nigeria.
Résumé
OBJECTIVE: To explore the effects of methyl jasmonic acid(MeJA), arachidonic acid(AA) and acetylsalicylic acid(ASA) on fucoxanthin production and PtZDS gene expression in Phaeodactylum tricornutum. METHODS: The full length cDNA of PtZDS gene in P. tricornutum was obtained by HiSeq™ Illumina 2000 and bioinformatics analysis. HPLC was used to determine the production of fucoxanthin in Phaeodactylum tricornutum, and RT-PCR was used to determine the expression level of PtZDS. RESULTS: The total length of PtZDS gene was 1 905 bp, containing an open reading frame of 1 776 bp encoding 591 amino acids. The deduced amino acid sequence analysis showed that PtZDS protein contained a typical amino oxidase domain, NAD(P)-binding Rossmann-like domain and a chloroplastic transit peptide sequence. The phylogenetic analysis demonstrated that PtZDS was homologous with Thalassiosira pseudonana CCMP1335(76%). Under the treatment of 0.1 mg·L-1 AA, 25 mg·L-1 ASA and 100 μmol·L-1MeJA, the highest yield of unit cell fucoxanthin content was achieved. Upon the observation of PtZDS regulation expression, the expression level of PtZDS reached a peak value under the treatment of 0.1 mg·L-1 AA, 50 μmol·L-1MeJA and 10 mg·L-1 ASA. CONCLUSION: The expression of PtZDS gene has certain relationship with the fucoxanthin synthesis of P. tricornutum. Under the treatment of 100 μmol·L-1 MeJA, the ability of synthetic fucoxanthinis the strongest in P. tricornutum.