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Appl. Environ. Microbiol., Sep 1995, 3503-3506, Vol 61, No. 9
UA Ochsner, J Reiser, A Fiechter and B Witholt
The high-level production of rhamnolipid biosurfactants is a unique feature
of Pseudomonas aeruginosa and is strictly regulated in response to
environmental conditions. The final step in rhamnolipid biosynthesis is
catalyzed by the rhlAB genes encoding a rhamnosyltransferase. The
expression of the cloned rhlAB genes was studied in heterologous hosts,
either under the control of the rhlR and rhlI rhamnolipid regulatory
elements or under the control of the tac promoter. A recombinant P.
fluorescens strain harboring multiple plasmid-encoded copies of the
rhamnolipid gene cluster produced rhamnolipids (0.25 g liter(sup-1)) when
grown under nitrogen-limiting conditions. The highest yields (0.6 g
liter(sup-1)) and productivities (24 mg liter(sup-1) h(sup-1)) were
obtained in a recombinant Pseudomonas putida strain, KT2442, harboring
promoterless rhlAB genes fused to the tac promoter on a plasmid. Active
rhamnosyltransferase was synthesized, but no rhamnolipids were produced, by
recombinant Escherichia coli upon induction of rhlAB gene expression.
Copyright © 1995, American Society for Microbiology
Production of Pseudomonas aeruginosa Rhamnolipid Biosurfactants in Heterologous Hosts
Institute of Biotechnology, Swiss Federal Institute of Technology, ETH-Honggerberg, CH-8093 Zurich, Switzerland
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