Abstract
Nutrient supplementation is common in microalgae cultivation to enhance the accumulation of biomass and biofunctional products, while the recovery mechanism from nutrient starvation is less investigated. In this study, the influence of remodeled carbon metabolism on cell cycle progression was explored by using different light wavelengths under N-repletion and N-recovery. The results suggested that blue light enhanced cell enlargement and red light promoted cell division under N-repletion. On the contrary, blue light promoted cell division by stimulating cell cycle progression under N-recovery. This interesting phenomenon was ascribed to different carbon metabolisms under N-repletion and N-recovery. Blue light promoted the recovery of photosystem II and redirected carbon skeletons into proteins under N-recovery, which potentially accelerated cell recovery and cell cycle progression. Although red light also facilitated the recovery of photosystem II, it mitigated the degradation of polysaccharide and then arrested almost all the cells in the G1 phase. By converting light wavelengths at the 12 h of N-recovery with blue light, red and white lights were proved to increase biomass concentration better than continuous blue light. These results revealed different mechanisms of cell metabolism of Chlamydomonas reinhardtii during N-recovery and could be applied to enhance cell vitality of microalgae from nutrient starvation and boost biomass production.
Highlights
Microalgae excel in adapting to various culturing conditions
light-emitting diode (LED) lights of white, blue, and red were chosen to explore the effects on the cell growth of C. reinhardtii in both N-repletion and N-recovery (Figure 1)
LED lights of white, blue, and red were chosen to explore the effects on the cell growth of C. reinhardtii in both N‐repletion and N‐recovery (Figure 1)
Summary
The advantages of microalgae in alleviating environmental issues and providing clean biofuels establish their competence in environmental and renewable energy arenas [1]. Their commercialized applications are challenged by the potential conflict between the cost of culturing processes and the revenue of bioproducts. The coordination of process-compatible products for specific market scenarios is considered as a promising orientation to improve the economic viability of microalgae production, which requires a comprehensive understanding of the relationship between microalgal cell growth and its biomass compositions [2,3]. As the cultivation process goes, nutrient concentration cannot afford subsequent cell growth; microalgae have to slow down growth and convert nutrients into storage forms, such as starch and lipid. After nutrients are re-provided to the starving environment would the progression of the cell cycle be activated to advocate cell growth and, subsequently, cell division
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