title: In situ extractive fermentation for the production of hexanoic acid from galactitol by Clostridium sp. BS-1.
abstract: Clostridium sp. BS-1 produces hexanoic acid as a metabolite using galactitol and enhanced hexanoic acid production was obtained by in situ extractive fermentation with Clostridium sp. BS-1 under an optimized medium composition. For medium optimization, five ingredients were selected as variables, and among them yeast extract, tryptone, and sodium butyrate were selected as significant variables according to a fractional factorial experimental design, a steepest ascent experimental design, and a Box-Behnken experimental design. The optimized medium had the following compositions in modified Clostridium acetobutyricum (mCAB) medium: 15.5gL(-1) of yeast extract, 10.13gL(-1) of tryptone, 0.04gL(-1) of FeSO4·7H2O, 0.85gL(-1) of sodium acetate, and 6.47gL(-1) of sodium butyrate. The predicted concentration of hexanoic acid with the optimized medium was 6.98gL(-1), and this was validated experimentally by producing 6.96gL(-1) of hexanoic acid with Clostridium sp. BS-1 under the optimized conditions. In situ extractive fermentation for hexanoic acid removal was then applied in a batch culture system with the optimized medium and 10% (v/v) alamine 336 in oleyl alcohol as an extractive solvent. The pH of the culture in the extractive fermentation was maintained at 5.4-5.6 by an acid balance between production and retrieval by extraction. During a 16 day culture, the hexanoic acid concentration in the solvent increased to 32gL(-1) while it was maintained in a range of 1-2gL(-1) in the medium. The maximum rate of hexanoic acid production was 0.34gL(-1)h(-1) in in situ extractive fermentation.
authors.affiliation: Department of Chemical Engineering, Hanyang University, 17 Hangdang-dong, Seongdong-gu, Seoul 133-791, Republic of Korea.
authors.forename: Byoung Seung
authors.initials: BS
authors.lastname: Jeon
authors.forename: Chuloo
authors.initials: C
authors.lastname: Moon
authors.forename: Byung-Chun
authors.initials: BC
authors.lastname: Kim
authors.forename: Hyunook
authors.initials: H
authors.lastname: Kim
authors.forename: Youngsoon
authors.initials: Y
authors.lastname: Um
authors.forename: Byoung-In
authors.initials: BI
authors.lastname: Sang
mesh_terms: D057005:Bioengineering / Q000379:methods; D002208:Caproates / Q000302:isolation & purification / Q000378:metabolism*; D003013:Clostridium / Q000254:growth & development / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D005285:Fermentation; D004376:Galactitol / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008954:Models, Biological; D012997:Solvents
chemical_list: D002208:Caproates; D003470:Culture Media; D012997:Solvents; D004376:Galactitol; C037652:hexanoic acid
keywords: Box–Behnken experimental design; Clostridium sp. BS-1; Fractional factorial experimental design; Galactitol; Hexanoic acid; In situ extractive fermentation