Submitted to: Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2006
Publication Date: 11/1/2006
Citation: Gunther, N.W., Nunez, A., Fortis, L.L., Solaiman, D. 2006. Proteomic based investigation of rhamnolipid production by Pseudomonas chlororaphis strain NRRL B-30761. Journal of Industrial Microbiology and Biotechnology 33:914-920. Interpretive Summary: The United States of America’s agricultural production of fats and oils currently exceeds the domestic demand for these commodities. In addition, increasing competition in the export market for these agricultural materials has resulted in a significant decline in the potential value of this resource. Our previous research detailed the discovery of a non-pathogenic bacterium harmless to humans, animals, and plants that is capable of making a valuable biosurfactant. Previous to our discovery the only known producers of this type of biosurfactant were disease-causing bacteria. Furthermore our bacterium was able to produce the biosurfactant while using a low value agricultural by-product as its sole food source and under less energy-requiring conditions than those of the pathogenic organisms. However, little is known about the biological processes by which this non-pathogenic organism produces the biosurfactant. This manuscript details our efforts to identify the proteins that the bacterium chooses to produce when it is actively manufacturing the biosurfactant. By knowing the proteins that the bacterium needs to make to produce the biosurfactants, we hope to increase our understanding of how the bacterium is able to make the biosurfactant. This hopefully will show us new ways we can encourage the bacterium to make even greater amounts of this useful product.
Technical Abstract: We recently reported that a strain of the non-pathogenic bacterial species Pseudomonas chlororaphis was capable of producing the biosurfactant molecule, rhamnolipids. Previous to this report the organisms known to produce rhamnolipids were almost exclusively pathogens. Additionally the newly described P. chlororaphis strain produced rhamnolipids at room temperature in static minimal media cultures, as opposed to all previous reports of rhamnolipid production which occurred at elevated temperatures in mechanically agitated cultures. The non-pathogenic nature and energy-conserving production conditions make the P. chlororaphis strain an attractive candidate for commercial rhamnolipid production. However, little characterization of molecular/biochemical processes in P. chlororaphis have ever been reported. Therefore in order to achieve a greater understanding of the process by which P. chlororaphis produces rhamnolipids a survey of the proteins differentially expressed during rhamnolipid production was performed. Separation and measurement of the bacteria’s proteome was achieved using Beckman Coulter’s Proteome Lab PF2D capillary based protein fractionation system. Statistical analysis of the resulting data identified differentially expressed proteins and known orthologues of those proteins were identified using an AB 4700 Proteomics Analyzer mass spectrometer system. A list of proteins differentially expressed by P. chlororaphis strain NRRL B-30761 during rhamnolipid production was generated from this work, and confirmed through a repetition of the entire separation process.