title: Reduction of acetone to isopropanol using producer gas fermenting microbes.
abstract: Gasification-fermentation is an emerging technology for the conversion of lignocellulosic materials into biofuels and specialty chemicals. For effective utilization of producer gas by fermenting bacteria, tar compounds produced in the gasification process are often removed by wet scrubbing techniques using acetone. In a preliminary study using biomass generated producer gas scrubbed with acetone, an accumulation of acetone and subsequent isopropanol production was observed. The effect of 2 g/L acetone concentrations in the fermentation media on growth and product distributions was studied with "Clostridium ragsdalei," also known as Clostridium strain P11 or P11, and Clostridium carboxidivorans P7 or P7. The reduction of acetone to isopropanol was possible with "C. ragsdalei," but not with P7. In P11 this reaction occurred rapidly when acetone was added in the acidogenic phase, but was 2.5 times slower when added in the solventogenic phase. Acetone at concentrations of 2 g/L did not affect the growth of P7, but ethanol increased by 41% and acetic acid concentrations decreased by 79%. In the fermentations using P11, growth was unaffected and ethanol concentrations increased by 55% when acetone was added in the acidogenic phase. Acetic acid concentrations increased by 19% in both the treatments where acetone was added. Our observations indicate that P11 has a secondary alcohol dehydrogenase that enables it to reduce acetone to isopropanol, while P7 lacks this enzyme. P11 offers an opportunity for biological production of isopropanol from acetone reduction in the presence of gaseous substrates (CO, CO₂, and H₂).
authors.affiliation: Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, Oklahoma 74078; telephone: +1-405-744-8416; fax: +1-405-744-6059.
authors.forename: Karthikeyan D
authors.initials: KD
authors.lastname: Ramachandriya
authors.forename: Mark R
authors.initials: MR
authors.lastname: Wilkins
authors.forename: Marthah J M
authors.initials: MJ
authors.lastname: Delorme
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Zhu
authors.forename: Dimple K
authors.initials: DK
authors.lastname: Kundiyana
authors.forename: Hasan K
authors.initials: HK
authors.lastname: Atiyeh
authors.forename: Raymond L
authors.initials: RL
authors.lastname: Huhnke
mesh_terms: D019840:2-Propanol / Q000378:metabolism*; D000096:Acetone / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism*; D003013:Clostridium / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D010084:Oxidation-Reduction
chemical_list: D000096:Acetone; D002245:Carbon Dioxide; D002248:Carbon Monoxide; D006859:Hydrogen; D019840:2-Propanol