Energy-efficient and environmentally friendly production of starch-rich duckweed biomass using nitrogen-limited cultivation

This is the authors' abstract. We don't add key points for this paper.

Here, we combined the aquatic cultivation of the energy crop duckweed and nitrogen limitation to quickly produce starch-rich biomass. Under N limitation, duckweed can quickly accumulate starch at up to 52.37 ± 0.57% (dry weight). In the process, nitrogen use efficiency (NUE) reached 61.3 ± 1.8 kg biomass kg−1 N, exceeding that of most cereals. In this paper, we elucidated for the first time the mechanism of the high NUE of duckweed under N limitation. First, duckweed possesses higher N transport ability than most cereals and trees and can efficiently accumulate abundant N in vivo under N-sufficient condition. In addition, under N limitation, the stable expression and activity of key enzymes related to both carbon fixation and N assimilation ensured normal biomass accumulation. Furthermore, the efficient ubiquitin-proteasome system (UPS) and autophagy activated the endogenous N remobilization and recycling. Combined with the sharp increase in the expression and activity of duckweed glutamine synthase (GS), duckweed can efficiently redistribute and reuse the endogenous N to support its growth and starch accumulation. Especially, sewage was used to duckweed pre-cultivation in pilot-scale experiment, the approach can simultaneously achieve starch production and wastewater treatment. In a word, this paper provides an environmentally friendly, cost-effective and promising technology for starch production.