Bacteria Metabolically Engineered for Enhanced Phytochelatin Production and Cadmium Accumulation

Abstract

ABSTRACT Phytochelatins (PCs) with good binding affinities for a wide range of heavy metals were exploited to develop microbial sorbents for cadmium removal. PC synthase from Schizosaccharomyces pombe (SpPCS) was overexpressed in Escherichia coli , resulting in PC synthesis and 7.5-times-higher Cd accumulation. The coexpression of a variant γ-glutamylcysteine synthetase desensitized to feedback inhibition (GshI*) increased the supply of the PC precursor glutathione, resulting in further increases of 10- and 2-fold in PC production and Cd accumulation, respectively. A Cd transporter, MntA, was expressed with SpPCS and GshI* to improve Cd uptake, resulting in a further 1.5-fold increase in Cd accumulation. The level of Cd accumulation in this recombinant E. coli strain (31.6 μmol/g [dry weight] of cells) was more than 25-fold higher than that in the control strain.