Submitted to: Fermentation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2022
Publication Date: 9/28/2022
Citation: Qureshi, N., Liu, S., Saha, B.C. 2022. Butyric acid production by fermentation: Employing potential of the novel Clostridium tyrobutyricum strain NRRL 67062. Fermentation. 8(10). Article 491. https://doi.org/10.3390/fermentation8100491.
DOI: https://doi.org/10.3390/fermentation8100491

Interpretive Summary: Butyric acid is a commodity chemical that has a market size of over 80 thousand metric tons per year. It is used in foods, animal feed, pharmaceuticals, perfumes, plastic, and plasticizers. While butyric acid can be produced via fermentation of sugars, currently it is produced using petroleum because of cost. Recently, ARS researchers were able to isolate a butyric acid producing bacterium with promising potential for high yields. In this study, the fermentation was optimized to produce over 70 grams per liter of butyric acid. This was accomplished using corn steep liquor (CSL) as an inexpensive source of nutrients. CSL is a byproduct of corn milling known to be rich in nutrients and in this study proved to be as effective as the expensive laboratory medium for producing butyric acid. Development of a cost-effective fermentation of sugars to butyric acid would directly benefit corn refiners by creating a new market for their glucose syrup and indirectly corn farmers by increasing market demand for corn.

Technical Abstract: In these studies, a novel strain of Clostridium tyrobutyricum NRRL 67062 was evaluated for glucose fermentation to produce butyric and acetic acids. The strain was evaluated for inhibition from glucose and butyric acid, fermentation production in a bioreactor with pH control growth, and growth with corn steep liquor as a nutrient source. Butyric acid inhibition studies suggested that this strain tolerates and produces up to 71 gL-1 total acids of which butyric acid was 58 gL-1 and acetic acid 13 gL-1 with a productivity of 0.69 gL-1h-1. In a pH controlled bioreactor fermentation, strain produced 57.86 gL-1 butyric acid and 12.88 gL-1 acetic acid thus producing 70.74 gL-1 total acids. This equates to a yield of 0.71 g of acid per g consumed glucose. The maximum cell concentration was 3.80 gL-1, which may have been the reason for high productivity in the batch culture. Finally corn steep liquor (CSL; a commercial nutrient solution) gave greater growth and acid production than the refined medium.