Premium
Carbon metabolism and product inhibition determine the epoxidation efficiency of solvent‐tolerant Pseudomonas sp. strain VLB120ΔC
Author(s) -
Park JinByung,
Bühler Bruno,
Panke Sven,
Witholt Bernard,
Schmid Andreas
Publication year - 2007
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.21496
Subject(s) - bioprocess , strain (injury) , chemistry , pseudomonas putida , product inhibition , styrene , solvent , catabolite repression , metabolism , biochemistry , styrene oxide , escherichia coli , organic chemistry , energy source , biology , enzyme , polymer , non competitive inhibition , paleontology , coal , gene , mutant , copolymer , anatomy
Utilization of solvent tolerant bacteria as biocatalysts has been suggested to enable or improve bioprocesses for the production of toxic compounds. Here, we studied the relevance of solvent (product) tolerance and inhibition, carbon metabolism, and the stability of biocatalytic activity in such a bioprocess. Styrene degrading Pseudomonas sp. strain VLB120 is shown to be solvent tolerant and was engineered to produce enantiopure ( S )‐styrene oxide from styrene. Whereas glucose as sole source for carbon and energy allowed efficient styrene epoxidation at rates up to 97 µmol/min/(g cell dry weight), citrate was found to repress epoxidation by the engineered Pseudomonas sp. strain VLB120ΔC emphasizing that carbon source selection and control is critical. In comparison to recombinant Escherichia coli , the VLB120ΔC‐strain tolerated higher toxic product levels but showed less stable activities during fed‐batch cultivation in a two‐liquid phase system. Epoxidation activities of the VLB120ΔC‐strain decreased at product concentrations above 130 mM in the organic phase. During continuous two‐liquid phase cultivations at organic‐phase product concentrations of up to 85 mM, the VLB120ΔC‐strain showed stable activities and, as compared to recombinant E. coli , a more efficient glucose metabolism resulting in a 22% higher volumetric productivity. Kinetic analyses indicated that activities were limited by the styrene concentration and not by other factors such as NADH availability or catabolite repression. In conclusion, the stability of activity of the solvent tolerant VLB120ΔC‐strain can be considered critical at elevated toxic product levels, whereas the efficient carbon and energy metabolism of this Pseudomonas strain augurs well for productive continuous processing. Biotechnol. Bioeng. 2007;98: 1219–1229. © 2007 Wiley Periodicals, Inc.