Discipline: Biological Sciences
Subcategory: Chemical/Bimolecular/Process Engineering
Session: 4
Room: Exhibit Hall
Anna Stankes - University of Texas at Austin
Co-Author(s): Ted Chavkin, University of Wisconsin; Emily Ayers, University of Wisconsin; Brian Pfleger, University of Wisconsin
The overapplication of fertilizers and subsequent nutrient runoff have a history of harming native ecosystems, commerce, and recreation. Algae blooms triggered by excess nutrients in water lower the oxygen concentration in lakes and rivers, killing wildlife and forcing communities to close lakes entirely, shutting down an important source of revenue. When fertilizers are applied, nutrient levels are often matched to the nitrogen demand of crops which results in other nutrients, primarily phosphorus, being large contributors to runoff.Farmers often dispose of dairy manure as fertilizer, applying excess to fields throughout the year; manure disposed of in this way far exceeds crop nutrient demands, resulting in high levels of runoff. We aim to increase the feasibility of using cyanobacteria as a phosphorus sequestration tool by growing it on dairy waste streams which contain both nitrogen and phosphorus. The cyanobacteria grown in this process can be stored in a dry form and reapplied later as a fertilizer or sold. Using cyanobacteria as a nutrient sequestration tool will provide an economically viable alternative to the reapplication of dairy manure to fields.We worked with the cyanobacteria strain Synechococcus sp. PCC 7002 to better understand its nutrient uptake behavior and improve its capability to sequester nutrients. To determine uptake versus growth, we used three shake flasks inoculated with PCC 7002 as well as a media flask to ensure nutrients were not being lost through evaporation. Growth was measured over the course of four days using OD 730, and nutrient uptake was obtained by spinning down 1000 μL of culture daily and quantifying the levels of nitrogen and phosphorus remaining in solution. We found phosphorus uptake and cell growth to have a consistent relationship over time, with mg P / gram dry cell weight being similar for all time points. Nitrogen uptake, when corrected for cell growth, showed an increase over time; cells at later time points exhibited a larger amount of sequestered nitrogen in the form of mg N / g dry cell weight. While the uptake rates and relationship with cell growth were different, both phosphorus and nitrogen were successfully sequestered by PCC 7002, with little if any nutrients lost to evaporation. The difference in cellular need for phosphorus and nitrogen will require additional consideration when deciding adequate feed stream composition.The procedure described should be repeated with other strains of cyanobacteria commonly used in research and engineering. Determining which cyanobacteria strain is best suited for nutrient storage would be valuable for optimizing sequestration from dairy manure. The maximum amount of phosphorus and nitrogen which can be stored should also be determined. Information regarding maximum storage capabilities and uptake rate would reveal the maximum potential sequestration efficiency of different strains.
Funder Acknowledgement(s): This work was supported through the NSF EFRI program.
Faculty Advisor: Ted Chavkin, tchavkin@wisc.edu
Role: I performed the nutrient uptake experiment described above. This included taking growth measurements over time and quantifying nitrogen and phosphorus uptake of the same culture. Nitrogen and phosphorus data was obtained by isolating media and determining mg uptake per gram dry cell weight at each time point.