Generation and Characterization of dszB mutants from Nocardia asteroides A3H1




Scott, Christopher A.

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Dibenzothiophene, a model compound for sulfur-containing organic molecules found in fossil fuels, can be desulfurized to 2-hydroxybiphenyl by Nocardia asteroides sp. strain A3H1 (A3H1) using the “4S” desulfurization pathway. In the final and rate-limiting step of this pathway, the DszB enzyme catalyzes the hydrolysis of 2-(2’- hydroxyphenyl) benzenesulfinate to form inorganic sulfur and 2-hydroxybiphenyl. The wildtype dszB gene from A3H1 was successfully cloned into the pBAD TOPO® and pBAD TOPO®/ThioFusion expression vectors. Cloning efficiency of the wildtype gene into the pBAD TOPO® vector was 86%. The in vitro directed evolution of DszB was initiated using error-prone PCR. An asexual dszB mutant library was generated and sixty mutant genes were characterized. The average mutation rate of the dszB gene was determined to be 0.75% ± 0.84. Attempts at overexpressing the mutant genes were unsuccessful and no measurable induction of fusion protein expression was observed upon arabinose addition.



desulfurization, Nocardia, petroleum products


Scott, C. A. (2003). Generation and characterization of dszB mutants from Nocardia asteroides A3H1 (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.


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