Understanding precision nitrogen stress to optimize the growth and lipid content tradeoff in oleaginous green microalgae

► N deficiency generally had disproportionate effects on growth and lipid content. ► Optimal growth and lipid balancing required wide range in N supply among species. ► Concurrent growth and lipid accumulation resulted in increased lipid productivity. ► High lipid content resulted from a lipid accumulation response to little stress. ► Best species will grow, accumulate lipid concurrently and respond to little stress. Nitrogen deficiency promotes lipid formation in many microalgae, but also limits growth and lipid productivity. In spite of numerous studies, there is poor understanding of the interactions of growth and lipid content, the time course of lipid accumulation and the magnitude of nitrogen deficiency required to stimulate lipid formation. These relationships were investigated in six species of oleaginous green algae, comparing high and low levels of deficiency. Nitrogen stress typically had disproportionate effects on growth and lipid content, with profound differences among species. Optimally balancing the tradeoffs required a wide range in nitrogen supply rate among species. Some species grew first and then accumulated lipids, while other species grew and accumulated lipids concurrently which resulted in increased lipid productivity. Accumulation of high lipid content generally resulted from a response to minimal stress. The data highlight the tremendous biodiversity that may be exploited to optimally produce lipids with precision nitrogen stress.