Submitted to: Fermentation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2024
Publication Date: 3/1/2024
Citation: Qureshi, N., Ashby, R.D., Nichols, N.N., Hector, R.E. 2024. Novel technologies for butyric acid fermentation: use of cellulosic biomass, rapid bioreactor, and efficient product recovery. Fermentation. https://doi.org/10.3390/fermentation10030142.
DOI: https://doi.org/10.3390/fermentation10030142

Interpretive Summary: Butyric acid has numerous applications including in food, feed, cosmetic, medical, pharmaceutical, fuel/biofuel, and aviation biofuel. For example, butyric acid can be converted to butanol, a drop in biofuel that is superior to ethanol because it has better fuel properties and higher energy content (than ethanol). Currently butyric acid is produced by a chemical/petrochemical process that is not environmentally friendly and contributes to global warming. This research resulted in production of butyric acid from low-cost cellulosic sugars and agricultural residues such as wheat straw and corn stover. In this study, biomass hydrolysis methods that are environmentally friendly were used. Production cost of this biological conversion process was reduced through use of low-cost biomass and application of bioprocess technology with increased efficiency. We developed a bioprocess technology that is superior to traditional methods of production and reduces process cost by greater than 800%. When commercialized it will benefit US farmers, biorefineries, aviation fuel/biofuel industry, and the US public. Further, use of this process over current production methods would benefit the environment by reducing global warming.

Technical Abstract: Butyric acid, a four-carbon fatty acid, is an important industrial chemical and feedstock. To produce this chemical, a control fermentation was run with 126.5 gL-1 glucose concentration in the feed medium. In this medium the strain produced 44.8 gL-1 total acid with a productivity of 0.23 gL-1h-1 and a yield of 0.41 g.g-1. The strain was also able to utilize glucose and xylose simultaneously with similar fermentation performance. The culture was also used to produce butyric acid from wheat straw hydrolysate (WSH) employing hot water pretreatment. In a batch system, the strain resulted in a productivity and yield of 0.27 gL-1h-1 and 0.44 g.g-1, respectively, which was an improvement over the use of glucose or xylose alone or mixtures of both. To improve reactor productivity a membrane cell recycle bioreactor was used which resulted in a productivity of 1.89 gL-1h-1. This productivity was 822% of that achieved in the glucose or xylose batch fermentation. Furthermore, a butyric acid recovery method was developed using XAD-4 adsorbent resin. In this system up to 206.1 gL-1 butyric acid was used in the feed and as a result of quick adsorption, the residual butyric acid concentration was 29.5 g.L-1. In this experiment the rate of acid removal of 1059.4 g.L-1h-1 was achieved.