高产DHA裂壶藻突变株发酵条件的优化Optimization of fermentation conditions of Schizochytrium sp. mutant with high DHA yield

Abstract

为了进一步提高裂壶藻突变株的DHA产量，以经过60Co-γ射线辐照诱变后所得高产DHA裂壶藻突变株1.6-7-1为研究对象，通过Plackett-Burman实验、最陡爬坡实验和响应面实验对其发酵培养基进行优化，同时通过发酵罐发酵培养研究不同溶氧水平对突变株代谢的影响。结果表明：葡萄糖、C5H8NNaO4和NaCl添加量对该突变株产DHA具有显著影响，其最佳添加量分别为葡萄糖125.46 g/L、C5H8NNaO4 12.44 g/L、NaCl 4 g/L，在此条件下该突变株DHA产量达6.01 g/L，相较于原始菌株提升了49.88%；在高溶氧水平下，突变株生物量高但油脂产量和DHA产量较低，可能是因为细胞优先用营养物质进行自身的生长繁殖，而过低的溶氧水平会抑制能量代谢，减慢细胞繁殖速度。综上，优化发酵条件可以提高突变株DHA产量。 Abstract：In order to further increase the DHA yield of Schizochytrium sp. mutant, the Schizochytrium sp. mutant 1.6-7-1 with high yield DHA obtained by 60Co-γ radiation mutagenesis was used as research object, and the fermentation medium of DHA production by the Schizochytrium sp. mutant was further optimized by Plackett-Burman experiment, steepest ascent experiment and response surface methodology. In addition, the effects of different dissolved oxygen levels on the metabolism of the mutant strain were investigated through fermentation cultivation in fermentation tank. The results showed that the dosages of glucose, sodium glutamate and NaCl had significant effects on the DHA production of the mutant strain, and their optimum dosages were glucose 125.46 g/L, sodium glutamate 12.44 g/L and NaCl 4 g/L. Under the optimum conditions, the DHA production could reach 6.01 g/L, which increased by 49.88% compared with the original strain.Under high dissolved oxygen conditions, the mutant strain exhibited higher biomass accumulation but lower oil and DHA production, which possibly caused by the preferential use of nutrients for the own growth and reproduction of cells. Conversely, low dissolved oxygen inhibited energy metabolism and slowed down cell proliferation. Therefore, optimizing fermentation conditions can increase the DHA yield of the mutant strain.

Keywords

• dha；裂壶藻；突变株；发酵条件优化
• dha; schistochytrum sp. ; mutant strain; optimization of fermentation conditions