ABSTRACT Microalgae are capable of accumulating biomass and high value-added products in mixotrophic culture. Carbon sources and light intensity have significant impacts on mixotrophic algal growth and metabolites accumulation. To investigate the underlying mechanism of interaction between metabolism of inorganic carbon and organic carbon, growth of Nannochloropsis oceanica with two different carbon sources (organic sodium acetate and inorganic sodium bicarbonate) and under three different light conditions (low, medium and high) was examined. A combination of sodium acetate and sodium bicarbonate significantly enhanced algal growth with higher acetate assimilation, when compared with single carbon sources. With increasing light intensity from low to high, the algal growth rates decreased in both autotrophic and mixotrophic cultures. Proteome and 13C metabolic flux results showed that acetate utilization via the glyoxylate (GOX) cycle was enhanced, and both the tricarboxylic acid (TCA) cycle and putative C4 pathway were stimulated in the presence of sodium acetate and sodium bicarbonate. These data suggest that sodium bicarbonate could facilitate acetate assimilation and enhance the putative C4 pathway, GOX cycle and TCA cycle in N. oceanica under mixotrophic culture conditions.

中文翻译：

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无机碳和光对混合营养培养中大洋小球藻（Eustigmatophyceae）醋酸盐同化的影响

摘要 微藻能够在混合营养培养中积累生物量和高附加值产品。碳源和光强度对混合营养藻类生长和代谢物积累有显着影响。为了研究无机碳和有机碳代谢之间相互作用的潜在机制，研究了具有两种不同碳源（有机醋酸钠和无机碳酸氢钠）和三种不同光照条件（低、中和高）的大洋藻的生长。与单一碳源相比，醋酸钠和碳酸氢钠的组合显着促进藻类生长，同时醋酸盐同化程度更高。随着光照强度从低到高的增加，自养和混养培养中的藻类生长率均下降。蛋白质组和 13C 代谢通量结果表明，通过乙醛酸 (GOX) 循环提高了乙酸盐利用率，并且在乙酸钠和碳酸氢钠存在下，三羧酸 (TCA) 循环和推定的 C4 途径均受到刺激。这些数据表明，在混合营养培养条件下，碳酸氢钠可以促进醋酸盐同化，并增强大洋海棠中假定的 C4 途径、GOX 循环和 TCA 循环。