High starch duckweed biomass production and its highly-efficient conversion to bioethanol

This paper carried out a new attempt which combined nutrient starvation, uniconazole and elevated CO2 to increase duckweed biomass and starch content. At laboratory level, the highest growth rate and starch content reached up to 9.4 ± 0.2 g m−2 d−1 and 75.9 ± 3.3 %, leading to an estimated starch yield of 30.8 t ha−1 y−1. Furthermore, without any pretreatment, up to 88.4 ± 0.4 % of glucose from high starch duckweed biomass can be released. The enzymatic hydrolyzates can be efficiently converted to bioethanol by yeast and the ethanol yield based on duckweed biomass input (YE/B) reached up to 0.38 ± 0.01 g g−1 applying simultaneous saccharification and fermentation (SSF), which, to our knowledge, is the highest duckweed-to-ethanol yield thus far reported. Based on the data above-mentioned, an annual duckweed-based ethanol yield of 16.0 × 103 L ha−1 can be achieved, about 2.6 times higher than maize-based ethanol yield. This approach has achieved quick high starch accumulation in duckweed and demonstrated that duckweed can serve as a competitive starch feedstock for bioethanol production.