Due to increasing global population, it is estimated that global food production must double by 2050 to meet population demands, and 70% of increased output must come from enhanced agricultural productivity and efficiency. There is a particular need for new sources of protein. University of Alabama-Birmingham (UAB) and Southern Research (SR) have established a program to focus on developing a deep scientific and engineering understanding of highly controlled duckweed growth as a platform for intensive protein production. This work will develop a new understanding of how to control the phenological cycle of duckweed by prolonging vegetative growth and maintaining the organisms in exponential growth phase for extended periods of time. The work will focus on development of new multiscale models to predict growth rates and harvest protocols for duckweed cultivation using a chemical and biosystems engineering perspective; and metabolic engineering of wild type duckweed to alter the pathways that control vegetative growth and nutrient uptake. The team expects to demonstrate duckweed biomass growth in open reactors using a various nutrient packages, including supplemental carbon potentially derived from the capture of industrial flue gas carbon dioxide as ammonium bicarbonate and excess nitrogen and phosphorous present in municipal and agriculture wastewaters. Preliminary results using wild type Spirodela polyrhiza grown in nitrogen and phosphorous-rich wastewaters show excellent growth rates, comparable to those seen with synthetic nutrition packages. We collected sewage and pond water from Star Lake (native site of culture collection) as a control. We re-cultivated the sterilized S. polyrhiza in pond and sewage water tanks using approximately 5% duckweed as starting material. We measured the growth of duckweed over time for 14 days and observed that percent growth of S. polyrhiza in sewage water reached 94% on day 7, while the duckweed in pond water obtained similar mass on day 11. We started to observe the onset of senescence in S. polyrhiza grown in pond water on the day 20, while we did not observe any senescence symptoms on duckweed grown in sewage water. We concluded that the growth rate of S. polyrhiza growth is significantly faster in sewage, and sewage water grown duckweed displayed delayed onset of senescence. The team anticipates that this work will inform scale-up of duckweed-based aquaculture systems for intensive protein production at a globally.

Intensive aquatic protein production using duckweed as a model platform

253rd National Meeting (2017)

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