High Saccharification, Low Lignin, and High Sustainability Potential Make Duckweeds Adequate as Bioenergy Feedstocks

Abstract

Duckweeds are the smallest free-floating aquatic monocots. They have a unique cell wall containing pectin polymers named apiogalacturonan and xylogalacturonan. Knowing that the cell wall composition is essential for duckweeds as a bioenergy feedstock, notably ethanol production, this work reports the five duckweed species’ (Spirodela polyrhiza, Landoltia punctata, Lemna gibba, Wolffiella caudata, and Wolffia borealis) composition and saccharification potential. Nonstructural carbohydrates were, on average, 42% of the dry weight. The cell wall comprises 20.1% pectin and glucomannan, 35.2% hemicelluloses, 30% cellulose, and 5% lignin, and the fermentable sugars in duckweed walls are glucose, galactose, and xylose. Together, these monosaccharides constitute 51.4% of the cell wall. Duckweeds displayed low recalcitrance to hydrolysis, probably due to the low lignin and cellulose contents. Furthermore, the saccharification of the duckweeds was higher than sugarcane, a primary bioethanol feedstock. Results indicate that duckweed biomass displays a high potential as a feedstock for bioethanol production.