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Int J Biol Sci 2009; 5(3):215-225. doi:10.7150/ijbs.5.215

Research Paper

Diverse protein regulations on PHA formation in Ralstonia eutropha on short chain organic acids

Sung-Eun Lee1,2,3, Qing X. Li1, Jian Yu2 ✉

1. Dapartment of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA;
2. Hawaii Natural Energy Institute, University of Hawaii at Manoa, Honolulu, HI 96822, USA;
3. Nanotoxtech. Inc., Dong-Yang Grafea 1114-Ho, Sunae-dong 6-2, Seongnam 463-708, Korea


Organic acids are considered as potential substrates for biosynthesis of polyhydroxyalkaonates. The acids may also be the metabolic inhibitors at moderate concentration levels. In this study, Ralstonia eutropha was used to elucidate the protein regulations when the bacterial cells pre-cultivated on glucose were exposed to three representative short chain organic acids, acetic, propionic and levulinic acids. The research compared and examined the proteins that might participate in PHA metabolism, primary metabolism, and cell's defense systems. A number of proteins were found to be induced in R. eutropha by using 1D-PAGE and nano-liquid chromatography tandem MS/MS. With the proteins being up-regulated, a dramatic change occurred in the induction of PHA metabolism, including fatty acid biosynthesis for acetate, β-oxidation for propionate and both for levulinic acid. Acetate kinase was induced in response to the presence of acetate or levulinic acid. The organic acids induced several proteins involved in amino acid biosynthesis, purine and pyrimidine biosynthesis, and cofactor biosynthesis in R. eutropha, but the regulations had a great variation. R. eutropha might employ different regulation mechanisms to maintain cell growth and PHA formation when the cells are exposed to the organic acids as sole source of carbon and energy.

Keywords: Ralstonia eutropha, LC-MS, MS, organic acids, proteomics, biopolymer

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) License. See for full terms and conditions.
How to cite this article:
Lee SE, Li QX, Yu J. Diverse protein regulations on PHA formation in Ralstonia eutropha on short chain organic acids. Int J Biol Sci 2009; 5(3):215-225. doi:10.7150/ijbs.5.215. Available from