Hydrogen sulfide improves lipid accumulation in Nannochloropsis oceanica through metabolic regulation of carbon allocation and energy supply

To utilize CO2 in syngas from coal gasification with H2S impurity for microalgal biodiesel production, metabolic regulation stimulated by NaHS (an H2S donor) of carbon allocation and energy supply in Nannochloropsis oceanica were investigated to improve lipid accumulation. Enzyme analysis showed that H2S (NaHS ≤ 0.5 mM) enhanced glycolysis and fatty acids synthesis, as well as suppressed the desaturation, elongation and degradation of fatty acids during intracellular carbon metabolism. Additionally, H2S transformed the main ATP synthesis pathway from oxidative phosphorylation to photophosphorylation and substrate phosphorylation, facilitating efficient energy supply during lipid accumulation. Raman spectra and transmission electron microscopy (TEM) showed that the peak rate of lipid accumulation increased by 60.2~62.2% in N. oceanica cells exposed to 0.5 mM NaHS. This markedly increased the yields of fatty acid methyl esters (FAMEs) and short chain FAMEs (C12:0 and C14:0) from N. oceanica cells by 77.0% a...