Limiting acetoin generation during 2,3-butanediol fermentation with Paenibacillus polymyxa using lignocellulosic hydrolysates

Authors: Stoklosa, Ryan; Garcia-Negron, Valerie; Latona, Renee; Toht, Matthew

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2023
Publication Date: 11/20/2023
Citation: Stoklosa, R.J., Garcia-Negron, V., Latona, R.J., Toht, M.J. 2023. Limiting acetoin generation during 2,3-butanediol fermentation with Paenibacillus polymyxa using lignocellulosic hydrolysates. Bioresource Technology. https://doi.org/10.1016/j.biortech.2023.130053.
DOI: https://doi.org/10.1016/j.biortech.2023.130053

Interpretive Summary: Reducing the amount of petroleum utilized for liquid transportation fuels can offset the release of detrimental greenhouse gases. The commercial aviation sector is aiming to lessen its reliance on petroleum based fuels by switching to Sustainable Aviation Fuels (SAF) that are produced from agricultural waste crops. One processing route for SAF generation is to first produce a platform chemical using microbial fermentation that can later be chemically upgraded to SAF. One such platform chemical that can be generated by bacteria using fermentation is 2,3-butanediol (2,3-BDO). This work investigated taking the remnants following corn harvest (corn stover) and switchgrass, and utilizing this plant material as a feedstock for 2,3-BDO production. The corn stover and switchgrass were processed using a lower severity alkaline pretreatment process, and were further deconstructed by enzymes to recover fermentable sugars. The sugars served as the carbon source for fermentation to produce 2,3-BDO. Fermentations conducted at larger scale (2 Liter volume) produced fast 2,3-BDO generation within 24 hours reaching 43 g/L. However, as the fermentation progressed the 2,3-BDO product output decreased due to the bacteria's ability to convert the 2,3-BDO into a different byproduct. While this research showed the potential for high 2,3-BDO production output through fermentation, additional research is required to optimize the process to eliminate byproduct formation and further increase 2,3-BDO generation.

Technical Abstract: Recent efforts to decarbonize the commercial aviation industry has led to renewed interests in generating sustainable aviation fuels (SAF) from agricultural feedstocks. One processing route for SAF production looks to utilize a bio-based platform chemical known as 2,3-butanediol (2,3-BDO) for catalytic conversion to hydrocarbons. In this work a mild alkaline pretreatment using sodium carbonate was performed on corn stover (CS) and switchgrass (SG) to generate hydrolysates for fermentation with the naturally producing 2,3-BDO bacteria Paenibacillius polymyxa. Enzymatic hydrolysis performed on the pretreated CS and SG produced theoretical sugar yields of 80% and 95% for glucan and xylan, respectively, for both feedstocks. Fermentations with P. polymxya conducted in sealed anaerobic bottles produced 2,3-BDO reaching concentrations ranging from 14-18 g/L with negligible conversion into acetoin. Bioreactor fermentations at the 2 L scale using the hydrolysate media generated up to 43 g/L and 34 g/L of 2,3-BDO from pretreated CS and SG, respectively, within the first 24 hours of fermentation. However, 2,3-BDO product output was reduced by 40-50% over the remainder of the fermentation due to back conversion into acetoin caused by glucose depletion.