DESULFURIZATION OF OXIDIZED BITUMEN USING MICROORGANISMS THROUGH PROCESS-BASED DIRECTED EVOLUTION

• Author / Creator

  De Man, Allison B

• Many Rhodococcus species are capable of utilizing the 4S biodesulfurization pathway to convert dibenzothiophene (DBT) to 2-hydroxybiphenyl (2-HBP) and sulfite, the latter of which is partially incorporated into cell biomass. The first steps of the 4S pathway involve the oxidation of DBT into DBTO2 for further conversion. It is hypothesized that using DBTO2 as the direct substrate for desulfurization would result in faster growth rates and increased desulfurization activity. Process-based directed evolution strategies were performed, using DBTO2 as a selective pressure, with three Rhodococcus species to adapt the cultures and select for mutants with increased desulfurization activity. Process-based directed evolution was performed through two strategies: (i) sequential transfers and (ii) self-cycling fermentation (SCF). A change in desulfurization activity for Rhodococcus rhodochrous IGTS8 was observed and indicated a change in sulfur management in the cell. Rhodococcus erythropolis EPWF developed a gain-of-function mutation that enabled it to desulfurize DBTO2.

• Subjects / Keywords

  • Dibenzothiophene Sulfone (DBTO2)
  • Biodesulfurization
  • Directed Evolution
  • Self-Cycling Fermentation (SCF)
  • Sequential Transfers
  • Rhodococcus

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3WH2DP37

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.