Butyric Acid Generation by Clostridium tyrobutyricum from Low-Moisture Anhydrous Ammonia (LMAA) Pretreated Sweet Sorghum
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Butyric Acid Generation by Clostridium tyrobutyricum from Low-Moisture Anhydrous Ammonia (LMAA) Pretreated Sweet Sorghum Bagasse Ryan J. Stoklosa 1
& Carrington Moore
1,2
1
& Renee J. Latona & Nhuan P. Nghiem
1
Received: 9 September 2020 / Accepted: 8 November 2020/ # This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2020
Abstract
Sweet sorghum bagasse (SSB) is an under-utilized feedstock for biochemical conversion to biofuels or high value chemicals. One such chemical that can be generated biochemically and applied to a wide array of industries from pharmaceuticals to the production of liquid transportation fuels is butyric acid. This work investigated cultivating the butyric acid producing strain Clostridium tyrobutyricum ATCC 25755 on low-moisture anhydrous ammonia (LMAA) pretreated SSB. Pretreated SSB hydrolysate was detoxified and supplemented with urea for shake flask batch fermentation to show that up to 11.4 g/L butyric acid could be produced with a selectivity of 87% compared to other organic acids. Bioreactor fermentation with pH control showed high biomass growth, but a similar output of 11.3 g/L butyric acid was achieved. However, the butyric acid productivity increased to 0.251 g/L∙hr with a butyric acid yield of 0.29 g/g sugar consumed. This butyric acid output represented an 83% theoretical yield. Further improvements in butyric acid titer and yield can be achieved by optimizing nutrient supplementation and incorporating fed-batch fermentation processing of pretreated SSB hydrolysate.
Keywords Sweet sorghum . Anhydrous ammonia . Clostridium tyrobutyricum . Butyric acid
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* Ryan J. Stoklosa [email protected]
1
Sustainable Biofuels and Co-Products Research Unit, Eastern Regional Research Center, USDA, ARS, Wyndmoor, PA 19038, USA
2
Present address: Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
Applied Biochemistry and Biotechnology
Introduction While corn ethanol biorefineries are able to meet current volumetric biofuel demand in the USA [1], agricultural producers and other stakeholders are still interested in expanding biofuel and high value chemical output by utilizing other agricultural feedstocks. The use of liquid transportation fuels is still expected to grow in demand and contribute to a 50% share in all transportation energy by the year 2075 [2]. This continued growth will necessitate greater production of biofuels and value-added chemicals. Additionally, a growing bioeconomy industry can offset and reduce fossil fuel usage, provide better food and energy security, and limit the effects of climate change through sustainably managed agricultural feedstock cultivation practices [3]. Cell
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