Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology , Tianjin University , Tianjin 300072 , PR China.
Key Laboratory of Systems Bioengineering (Ministry of Education) , Tianjin University , Tianjin 300072 , PR China.
J Agric Food Chem. 2018 Oct 10;66(40):10640-10650. doi: 10.1021/acs.jafc.8b03634. Epub 2018 Oct 1.
It is well-known that high-nitrogen content inhibits cell growth and docosahexaenoic acid (DHA) biosynthesis in heterotrophic microalgae Crypthecodinium cohnii. In this study, two nitrogen feeding strategies, pulse-feeding and continuous-feeding, were evaluated to alleviate high-nitrogen inhibition effects on C. cohnii. The results showed that continuous-feeding with a medium solution containing 50% ( w/v) yeast extract at 2.1 mL/h during 12-96 h was the optimal nitrogen feeding strategy for the fermentation process, when glucose concentration was maintained at 15-27 g/L during the same period. With the optimized strategy, 71.2 g/L of dry cell weight and DHA productivity of 57.1 mg/L/h were achieved. In addition, metabolomic analysis was applied to determine the metabolic changes during different nitrogen feeding conditions, and the changes in amino acids, polysaccharides, purines, and pentose phosphate pathway were observed, providing valuable metabolite-level information for exploring the mechanism of the high-nitrogen inhibition effect and further improving DHA productivity in C. cohnii.
众所周知，高氮含量会抑制异养微藻裂殖壶菌细胞生长和二十二碳六烯酸（DHA）的生物合成。在这项研究中，评估了两种氮源供给策略，即脉冲式供给和连续式供给，以减轻高氮对裂殖壶菌的抑制作用。结果表明，在 12-96 h 期间以 2.1 mL/h 的速度连续供给含有 50%（w/v）酵母提取物的培养基溶液是发酵过程的最佳氮源供给策略，在此期间葡萄糖浓度保持在 15-27 g/L。采用优化的策略，可获得 71.2 g/L 的干细胞重量和 57.1 mg/L/h 的 DHA 生产力。此外，还应用代谢组学分析来确定不同氮源供给条件下的代谢变化，观察到氨基酸、多糖、嘌呤和戊糖磷酸途径的变化，为探索高氮抑制作用的机制以及进一步提高裂殖壶菌中 DHA 的生产力提供了有价值的代谢物水平信息。
