P-253 - Optimizing duckweed cultivation: Cobalt’s role in vitamin B12 synthesis and bacterial community dynamics

As demand for sustainable, nutrient-rich crops grows, duckweed has emerged as a promising nutritional source due to its high protein content (up to 40% dry biomass) and vitamins, including B12. Since plants cannot synthesize or use B₁₂, its presence in duckweed relies on its endophytic microbiome. Understanding how cultivation conditions affect microbial B₁₂ production is key to optimizing duckweed’s nutritional value. We investigated how cobalt supplementation affects duckweed growth, vitamin B₁₂ synthesis, and endophyte composition. As cobalt is scarce, bacteria must scavenge for this resource. We hypothesized that supplementation would reduce this constraint, altering microbial dynamics and enhancing B₁₂ biosynthesis. To test our hypothesis, three duckweed species (Lemna minor, Wolffia globosa, and Spirodela polyrhiza) were cultivated at cobalt concentrations ranging from 0 to just below toxic levels (1 μM). Our results reveal up to a fivefold increase in vitamin B₁₂ content across species. Moreover, bacterial community analysis showed shifts in endophyte composition, reflecting a transition from cobalt scavenging to enhanced B₁₂ production. These findings suggest that nutrient availability shapes microbial interactions, influencing both community structure and metabolic function. This study shows the potential of targeted cultivation strategies to enhance plant-associated microbial functions, providing scalable protocols for sustainable agriculture and biofortification.