January 1, 2011.
Corn stover biomass can be pretreaed and hydrolyzed into soluble sugars to be fermented by microorganisms to ethanol. NREL has developed a recombinant bacteria Zymomonas mobilis 8b that metabolizes both five and six carbon sugars. During pretreatment, toxic inhibitors such as furfural and acetate are produced. NREL has made an attempt to adapt two sub-strains of Z. mobilis 8b to acetate and furfural by using a chemostat method. During the chemostat process, cultures were frozen back in glycerol and saved. In this study, those frozen cultures were revived and analyzed for performance in environments with varying concentrations of furfural and acetate. Growth was recorded every ten minutes by measuring the optical density of the samples. Growth curves were plotted to determine the period of steady cell growth and sugar utilization. The growth rates of fifteen sub-strains were then compared to an un-adapted 8b strain. Small scale fermentations were used to measure the amount of glucose, xylose, acetate, and ethanol at zero and tewntyfour hours in order to determine glucose utilization, xylose utilization, and ethanol production yeild. It is unclear whether or not either of the two sub strains improved over the duration of the chemostat. Compared to 8b, neither strain seemed to perform any better in the presence of furfural or acetate. To confirm these results, an analysis of the strains in corn stover hydrolyzate should be conducted. Further screening of strains isolated from different adaptation methods may produce more positive results.
Bacteriology | Cell Biology | Molecular Biology | Organismal Biological Physiology
National Renewable Energy Laboratory (NREL)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation.