Production of deuterated biomass by cultivation of Lemna minor (duckweed) in D2O
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Common duckweed Lemna minor was cultivated in 50% D2O to produce biomass with 50–60% deuterium incorporation containing cellulose with degree of polymerization close (85%) to that of H2O-grown controls.
The small aquatic plant duckweed, particularly the genus Lemna, widely used for toxicity testing, has been proposed as a potential source of biomass for conversion into biofuels as well as a platform for production of pharmaceuticals and specialty chemicals. Ability to produce deuterium-substituted duckweed can potentially extend the range of useful products as well as assist process improvement. Cultivation of these plants under deuterating conditions was previously been reported to require addition of kinetin to induce growth and was hampered by anomalies in cellular morphology and protein metabolism. Here, we report the production of biomass with 50–60% deuterium incorporation by long-term photoheterotrophic growth of common duckweed Lemna minor in 50% D2O with 0.5% glucose. L. minor grown in 50% D2O without addition of kinetin exhibited a lag phase twice that of H2O-grown controls, before start of log phase growth at 40% of control rates. Compared to continuous white fluorescent light, growth rates increased fivefold for H2O and twofold for 50% D2O when plants were illuminated at higher intensity with a metal halide lamp and a diurnal cycle of 12-h light/12-h dark. Deuterium incorporation was determined by a combination of 1H and 2H nuclear magnetic resonance (NMR) to be 40–60%. The cellulose from the deuterated plants had an average-number degree of polymerization (DPn) and polydispersity index (PDI) close to that of H2O-grown controls, while Klason lignin content was reduced. The only major gross morphological change noted was root inhibition.
KeywordsLemna minor Duckweed Biomass Deuteration Cellulose Nuclear magnetic resonance
This research was supported by the U. S. Department of Energy, Office of Science, through the Genomic Science Program, Office of Biological and Environmental Research, under Contract FWP ERKP752. The research at Oak Ridge National Laboratory’s Center for Structural Molecular Biology (CSMB) was supported by the U. S. Department of Energy, Office of Science, through the Office of Biological and Environmental Research under Contract FWP ERKP291, using facilities supported by the Office of Basic Energy Sciences, U. S. Department of Energy. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U. S. Department of Energy under Contract DE-AC05-00OR22725. D. Reeves was supported by a U. S. Department of Energy Higher Education Research Experience internship managed by Oak Ridge Institute of Science and Education. C. Rempe was supported by a Department of Energy Science Undergraduate Laboratory Internship and Higher Education Research Experience internship managed by Oak Ridge Institute of Science and Education. K. McGrath was supported by the DOE Academies Creating Teacher Scientists (ACTS) summer 2010 program.
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Conflict of interest
The authors declare no conflict of interest.
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