Cobalamin production in phototrophic and mixotrophic cultures of nine duckweed species (Lemnaceae)

To feed the rapidly increasing world population, food production will have to double while the amount of water and arable land remain unchanged. Therefore, we must transition to environmentally sustainable, but just as nutritious diets by 2050. This will require drastic reduction in animal-based foods and increasing plant-based foods. Plant- based diets are more sustainable and healthier, with but one exception, plants are low in cobalamin (vitamin B12). Only a few plant and fungi species contain cobalamin, and some of the cobalamin forms present in algae and mushrooms are not available to humans. Recently, the smallest known plant, the edible duckweed Wolffia globosa Mankai, was shown to contain high concentrations of bioavailable cobalamin. We hypothesized that the production of bioavailable cobalamin is not unique to W. globosa Mankai but is common to other duckweed species. We also hypothesized that cobalamin production depends on the conditions under which the duckweed is grown. To test our hypotheses, we cultivated nine duckweed species under mixotrophic and phototrophic conditions, then measured the concentration and identified the bioavailability of cobalamin using biological and analytical methods. Our results showed that all duckweed species tested produce bioavailable cobalamin while pseudocobalamin (the non-available form of cobalamin) was not detected. We also found that mixotrophic conditions enhanced duckweed growth but reduced cobalamin concentrations. Our results establish duckweed species as a novel source of plant-derived bioavailable cobalamin and highlight the effect of growth conditions on production. More research is needed to identify the bacteria responsible for the production of cobalamin in duckweed and to optimize the conditions for cobalamin production.