Reconstruction of a functional duckweed holobiont to reduce nutrient competition with microalgae for high-yield biomass production.

Abstract

Duckweed has been highlighted as an appropriate biomass for low-carbon industries because of its significantly high production rate and multiple resource value. However, the outbreak of microalgae is a practical issue that decreases duckweed production yield. This study demonstrated that the growth of the duckweed Lemna aequinoctialis from factory wastewater was enhanced by colonization with indigenous plant growth-promoting bacteria (PGPB), whereas the growth of a duckweed competitor microalga, Coelastrella sp. KC10, from the same wastewater was reduced by indigenous microalgal growth-inhibiting bacteria (MGIB). Finally, a quadruple co-culture of a synthetic duckweed holobiont, L. aequinoctialis colonized by both KLaR20 (PGPB) and KLaR16 (MGIB), and Coelastrella sp. KC10 successfully recovered the duckweed production level by 117.5% in frond number and 84.5% in dry weight in the absence of microalgae. This case study demonstrates for the first time that duckweed holobionts can be reconstructed and enforced to antagonize growth competitor microalgae.