Submitted to: Frontiers in Chemical Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2022
Publication Date: 11/4/2022
Citation: Stoklosa, R.J., Latona, R.J., Johnston, D. 2022. Assessing oxygen limiting fermentation conditions for 2,3-butanediol production from paenibacillus polymyxa. Frontiers in Chemical Engineering. 4:1038311. https://doi.org/10.3389/fceng.2022.1038311.
Interpretive Summary: The production of biofuels from plant biomass offers one solution to reducing the amount of petroleum-based fuels utilized in the transportation sector. Ethanol from corn grain remains the largest volume biofuel currently produced by the United States. However, ethanol as a liquid transportation fuel can only be utilized by most standard automobiles. A more recent goal set up by policy makers in the US is to increase the production of sustainable aviation fuel (SAF) for commercial airliners. One processing route to generate SAF would combine a fermentation process using sugars from plants that are converted to a platform chemical that can then be upgraded to a fuel in downstream processing. This work investigates the production of the platform chemical 2,3-butanediol (2,3-BDO) from the bacteria Paenibacillus polymyxa. A fermentation process was studied to determine the effect of oxygen on both the growth of the bacteria and associated 2,3-BDO generation. Fermentations were conducted either in the presence of oxygen, or in an oxygen limited environment. Sugars sourced from different plant material could be converted to 2,3-BDO and support bacterial growth for both fermentation conditions, but 2,3-BDO yields were higher in the oxygen limited environment. The processing parameters developed here will next be implemented in a larger scale fermentation process to generate higher concentrations of 2,3-BDO.
Technical Abstract: 2,3-butanediol (2,3-BDO) is a platform chemical that can be converted to a wide array of products ranging from bio-based materials to sustainable aviation fuel. This chemical can be produced by a variety of microorganisms in fermentation processes. Challenges remain for high titer 2,3-BDO production during fermentation due to several parameters, but controlling oxygen is one of the most relevant processing parameters to ensure viable product output. This work investigated the fermentation of plant biomass sugars by the 2,3-BDO producer Paenibacillus polymyxa. Aerobic and oxygen limited fermentation conditions were initially evaluated using molasses-based media to determine cell growth and 2,3-BDO output. Similar conditions were then evaluated on hydrolysate from pretreated sweet sorghum bagasse (SSB) that contained fermentable sugars from structural polysaccharides. Fermentations in molasses media under aerobic conditions found that 2,3-BDO could be generated, but over time the amount of 2,3-BDO decreased due to conversion back into acetoin. Oxygen limited fermentation conditions exhibited improved biomass growth, but only limited suppression of 2,3-BDO conversion to acetoin occurred. Glucose depletion appeared to have a greater role influencing 2,3-BDO conversion back into acetoin. Further improvements in 2,3-BDO yields were found by utilizing detoxified SSB hydrolysate.