In Situ Biphasic Extractive Fermentation for Hexanoic Acid Production from Sucrose by Megasphaera elsdenii NCIMB 702410

Abstract

Hexanoic acid production by a bacterium using sucrose as an economic carbon source was studied under conditions in which hexanoic acid was continuously extracted by liquid-liquid extraction. Megasphaera elsdenii NCIMB 702410, selected from five M. elsdenii strains, produced 4.69 g l⁻¹ hexanoic acid in a basal medium containing sucrose. Production increased to 8.19 g l⁻¹ when the medium was supplemented by 5 g l⁻¹ sodium butyrate. A biphasic liquid-liquid extraction system with 10 % (v/v) alamine 336 in oleyl alcohol as a solvent was evaluated in a continuous stirred-tank reactor held at pH 6. Over 90 % (w/w) of the hexanoic acid in a 0.5 M aqueous solution was transferred to the extraction solvent within 10 h. Cell growth was not significantly inhibited by direct contact of the fermentation broth with the extraction solvent. The system produced 28.42 g l⁻¹ of hexanoic acid from 54.85 g l⁻¹ of sucrose during 144 h of culture, and 26.52 and 1.90 g l⁻¹ of hexanoic acid was accumulated in the extraction solvent and the aqueous fermentation broth, respectively. The productivity and yield of hexanoic acid were 0.20 g l⁻¹ h⁻¹ and 0.50 g g⁻¹ sucrose, respectively.

Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate

“…Cultures with oleyl alcohol exhibited enhanced bacterial growth compared to the control and utilized 75% of the glucose. This result suggests that oleyl alcohol has low toxicity and that it extracts carboxylic acids, as previously described by Choi et al [20]. The reactive compounds, THA and TOA, were also tested at two concentrations diluted in oleyl alcohol.…”

“…elsdenii NCIMB702410, a strain chosen based on the screening work performed by Choi, et al [20], was purchased from the National Collection of Industrial, Food and Marine Bacteria (NCIMB) in the United Kingdom. The strain was revived in Peptone Yeast Glucose (PYG) media, adapted from Choi et al [20] and contained the following components in grams per liter of water: yeast extract (Becton Dickinson, Franklin Lakes, NJ, USA), 10 g; tryptone (Becton Dickinson, Franklin Lakes, NJ, USA), 5 g; peptone (Becton Dickinson, Franklin Lakes, NJ, USA), 5 g; beef extract (Sigma-Aldrich, St. Louis, MO, USA), 5 g; glucose (Caisson Labs, North Logan, UT, USA), 40 g; K 2 HPO 4 (Sigma-Aldrich, St. Louis, MO, USA), 2.04 g; KH 2 PO 4 (Sigma-Aldrich, St. Louis, MO, USA), 0.04 g; cysteine-HCl (Sigma-Aldrich, St. Louis, MO, USA), 0.5 g; CaCl 2 ·2H 2 O (Sigma-Aldrich, St. Louis, MO, USA), 0.01 g; MgSO 4 ·7H 2 O (Sigma-Aldrich, St. Louis, MO, USA), 0.02 g; NaHCO 3 (Sigma-Aldrich, St. Louis, MO, USA), 0.4 g; NaCl (Fisher Chemicals, Fairlawn, NJ, USA), 0.08 g; resazurin (Sigma-Aldrich, St. Louis, MO, USA), 1 mg; hemin solution, 10 mL; and vitamin K1 solution, 0.2 mL. The hemin solution was prepared by dissolving 50 mg of hemin (Sigma-Aldrich, St. Louis, MO, USA) in 1 mL of 1 M NaOH then adjusted up to 100 mL with water.…”

“…The reactive compounds are typically diluted in an organic solvent. Tri-alkyl amines have been reported to be effective as reactive compounds for acid extraction [11,20,30,34]. In the current work, we use pure THA and TOA.…”

“…In the current work, we use pure THA and TOA. Oleyl alcohol is one of the most common diluents for in situ extraction [11,20,30] and octanol has also been identified as highly effective for succinic acid extractions [29].…”

“…In a reactive extraction, only the protonated form of the acid is extracted and consequently, extraction is more efficient at low pH [20]. AA, BA, and HA all have similar pKa values of approximately 4.8.…”