Document Detail

Fatty acid cosubstrates provide β-oxidation precursors for rhamnolipid biosynthesis in Pseudomonas aeruginosa, as evidenced by isotope tracing and gene expression assays.
MedLine Citation:
PMID:  23042167     Owner:  NLM     Status:  MEDLINE    
Rhamnolipids have multiple potential applications as "green" surfactants for industry, remediation, and medicine. As a result, they have been intensively investigated to add to our understanding of their biosynthesis and improve yields. Several studies have noted that the addition of a fatty acid cosubstrate increases rhamnolipid yields, but a metabolic explanation has not been offered, partly because biosynthesis studies to date have used sugar or sugar derivatives as the carbon source. The objective of this study was to investigate the role of fatty acid cosubstrates in improving rhamnolipid biosynthesis. A combination of stable isotope tracing and gene expression assays was used to identify lipid precursors and potential lipid metabolic pathways used in rhamnolipid synthesis when fatty acid cosubstrates are present. To this end, we compared the rhamnolipids produced and their yields using either glucose alone or glucose and octadecanoic acid-d(35) as cosubstrates. Using a combination of sugar and fatty acids, the rhamnolipid yield was significantly higher (i.e., doubled) than when glucose was used alone. Two patterns of deuterium incorporation (either 1 or 15 deuterium atoms) in a single Rha-C(10) lipid chain were observed for octadecanoic acid-d(35) treatment, indicating that in the presence of a fatty acid cosubstrate, both de novo fatty acid synthesis and β-oxidation are used to provide lipid precursors for rhamnolipids. Gene expression assays showed a 200- to 600-fold increase in the expression of rhlA and rhlB rhamnolipid biosynthesis genes and a more modest increase of 3- to 4-fold of the fadA β-oxidation pathway gene when octadecanoic acid was present. Taken together, these results suggest that the simultaneous use of de novo fatty acid synthesis and β-oxidation pathways allows for higher production of lipid precursors, resulting in increased rhamnolipid yields.
Lin Zhang; Tracey A Veres-Schalnat; Arpad Somogyi; Jeanne E Pemberton; Raina M Maier
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-10-05
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  78     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-11-19     Completed Date:  2013-04-22     Revised Date:  2013-07-11    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8611-22     Citation Subset:  IM    
Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, USA.
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MeSH Terms
Carbohydrate Metabolism
Fatty Acids / metabolism*
Gene Expression Profiling
Glycolipids / metabolism*
Isotope Labeling
Isotopes / metabolism
Metabolic Networks and Pathways / genetics
Pseudomonas aeruginosa / genetics,  metabolism*
Reg. No./Substance:
0/Fatty Acids; 0/Glycolipids; 0/Isotopes; 0/rhamnolipid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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