Bacterial‐Triggered Triglyceride Synthesis in Coccomyxa subellipsoidea Coincident with Bioremediation of EPA‐Regulated Municipal Wastewater
Authors: Nicodemus Timothy , Black Paul 
Published: June 2021

The availability of clean water and sustainable food and energy production represents significant challenges for the next century, which emphasizes the importance renewable and energetically neutral methods that can be deployed in the developing and developed world. Coccomyxa subellipsoidea, a unicellular green microalga isolated from the Antarctic, is of particular interest due to [1] sustained growth over a range of temperate climates, [2] ability to accumulate high levels of triglycerides under abiotic stress conditions for potential use in biofuel/bioproduct production, [3] providing biomass for slow‐release nitrogenous biofertilizers and [4] potential as a catalytic organism in the process of bioremediation of EPA‐regulated wastewater. The introduction of abiotic stress conditions (including nitrogen deprivation) on C. subellipsoidea is costly and energetically unfavorable resulting in a significant decrease in chloroplast integrity, which is correlated with decreases in biomass, triglyceride accumulation and function in bioremediation. In order for C. subellipsoidea to be deployed in these interrelated processes, methods must be developed to promote growth and the generation of biomass in concert with high levels of triglyceride synthesis and use in bioremediation. This research has developed a co‐culture phototrophic growth system using C. subellipsoidea and a mixture of proprietary denitrifying bacteria. Using Bold's Basal Media (BBM) and standard growth conditions, culturing C. subellipsoidea with denitrifying bacteria induces high levels of triglyceride accumulation production in the alga without a loss of biomass; the control C. subellipsoidea alone does not accumulate triglyceride. These observations led to the hypothesis that the denitrifying bacteria produce a soluble signal that induces metabolic pathways in C. subellipsoidea required for triglyceride synthesis. When the bacteria are grown independently, harvested by centrifugation and the spent media autoclaved and mixed with new BBM, C. subellipsoidea begins to accumulate significant levels of triglyceride within four days of growth in support of the hypothesis. These studies suggest the denitrifying bacteria are not needed to elicit the lipogenic response in the alga, and that these bacteria secrete a small molecule effector that is thermostable. In the co‐culture system, EVOS fluorescent microscopy shows chloroplast integrity is maintained as reflected by size, shape and chlorophyll content. Further, there is not a reduction in biomass of C. subellipsoidea using the co‐culture system. In the context of wastewater bioremediation system, this work has demonstrated the denitrifying bacteria when co‐cultured with C. subellipsoidea using EPA‐regulated municipal wastewater further increases the ability of the algae to grow and accumulate biomass and triglyceride.Support or Funding InformationSupported by the Nebraska Department of Economic Development and Vestal W2O, Hastings NEThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.