ARS | Publication request: Production of Acetone Butanol (Ab) from Agricultural Residues Using Clostridium Acetobutylicum in Batch Reactors Coupled with Product Recovery

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: May 21, 2006
Publication Date: May 21, 2006
Citation: Qureshi, N., Saha, B.C., Hughes, S.R., Cotta, M.A. 2006. Production of acetone butanol (AB) from agricultural residues using Clostridium acetobutylicum in batch reactors coupled with product recovery [abstract]. Proceedings of the Ninth International Workshop on the Regulation of Metabolism, Genetics, and Development of the Solvent and Acid Forming Clostridia. p. 29.

Technical Abstract: Substrate cost is one of the most important factors that affects price of butanol production by fermentation. For this reason, use of economically available substrates such as agricultural residues should be investigated. Hence, wheat straw (WS) was chosen for the present studies for acetone butanol (AB) production using Clostridium acetobutylicum. Wheat straw (86 g WS/L total solution vol) was pretreated using 10 g/L sulfuric acid (121 deg C for 1 h) and saccharified with enzymes containing cellulase, beta-glucosidase, and xylanase (pH 5.0 (adjusted with 10M NaOH), 45 deg C for 72 h). After hydrolysis, pH was increased to 6.5 with 4M NaOH/KOH followed by filter sterilization. Fermentation was initiated by inoculating actively growing cells of C. acetobutylicum (P260). Batch fermentation was complete in less than 48 h, producing 23.5 g/L AB from the hydrolysate as compared to 19.5 g/L AB from 60 g/L glucose solution (control). Hydrolysates of agricultural residues often contain fermentation inhibitors (sugar degradation products). However, in the present case, no sign of inhibition was observed as the culture produced a higher amount of AB from wheat straw hydrolysate (WSH). Furthermore, possibilities of fermenting concentrated sugar solutions were investigated. The culture was able to grow and produce AB in up to 200 g/L sugar solution. In this fermentation, sugar utilization was incomplete, leaving behind approximately 140 g/L residual sugar in the broth. Next, AB was produced from WSH supplemented with 120-140 g/L glucose. In these experiments, the AB produced was simultaneously recovered by a novel product separation technique until all the sugar was utilized. This demonstrated that WSH can be used successfully for AB production from concentrated WSH/sugar solutions using C. acetobutylicum coupled with product recovery.