Enhanced biohydrogen and lipid coproduction in Chlorella protothecoides under nitrogen-limiting conditions in a closed system

This study was developed to explore the feasibility of achieving enhanced hydrogen (H-2) and lipid coproduction mediated by H-2-producing microalgae Chlorella protothecoides. C. protothecoides was able to simultaneously produce both H-2 and lipids, and this H-2 and lipid coproduction was found to be inducible under conditions of nitrogen limitation in a closed system. Specifically, optimal H-2 (151.1 mL L-1) and lipid (49.6% DW) coproduction was achieved under 5% N in a closed system. Relative to nitrogen-replete conditions, such nitrogen limitation was able to induce the accumulation of NADPH and reactive oxygen species, thereby directly promoting lipid production. Moreover, in a closed system, these limited nitrogen levels established conditions of anaerobiosis, activating hydrogenase and thereby generating H-2 while suppressing respiratory electron transport, ultimately further augmenting lipid production. Together, these results highlight a novel approach to simultaneously producing H-2 and lipids and to enhancing such coproduction activity.

Automated summary

This study found that simultaneous hydrogen and lipid coproduction could be achieved by using nitrogen limitation in a closed system with Chlorella protothecoides. Nitrogen limitation induced coproduction by accumulating NADPH and reactive oxygen species, promoting lipid production. In addition, nitrogen limitation established anaerobic conditions, activating hydrogenase and inhibiting respiratory electron transport, further enhancing lipid production.