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Analysis of an engineered sulfate reduction pathway and cadmium precipitation on the cell surface
Author(s) -
Wang Clifford L.,
Clark Douglas S.,
Keasling Jay D.
Publication year - 2001
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.10030
Subject(s) - chemistry , cadmium , hydrogen sulfide , sulfide , cysteine , cadmium sulfide , cystathionine gamma lyase , sulfate , inorganic chemistry , precipitation , biochemistry , sulfur , enzyme , organic chemistry , cystathionine beta synthase , physics , meteorology
We previously have genetically engineered an aerobic sulfate reduction pathway in Escherichia coli for the generation of hydrogen sulfide and demonstrated the pathway's utility in the precipitation of cadmium. To engineer the pathway, the assimilatory sulfate reduction pathway was modified so that cysteine was overproduced. Excess cysteine was then converted by cysteine desulfhydrase to an abundance of hydrogen sulfide, which then reacted with aqueous cadmium to form cadmium sulfide. In this study, observations of various E. coli clones were combined with an analysis of kinetic and transport phenomena. This analysis revealed that cysteine production is the rate‐limiting step in the engineered pathway and provided an explanation for the phenomenon of cell surface precipitation. An analytical model showed that cadmium sulfide must form at the cell surface because the rate of cadmium sulfide formation is extremely fast and the rate of sulfide transport is relatively slow. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 285–291, 2001.