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Optimization of Production and Recovery of Rhamnolipids and Study of Their Effect on Bacterial Attachment

Sodagari, Maysam
http://rave.ohiolink.edu/etdc/view?acc_num=akron1385081228

Abstract Details

2013, Doctor of Philosophy, University of Akron, Chemical Engineering.
Biosurfactans produced by microorganisms have been considered as a potential alternative to petrochemical derived surfactants. Among the most promising biosurfactants, rhamnolipids have applications as bioremediation enhancers, detergents, antibacterial, anti-biofouling agents and pharmaceuticals. Rhamnolipids are typically produced by the bacterium Pseudomonas aeruginosa. The main operational challenges of rhamnolipid production are the extreme foaming property of broth in aerobic fermentation and the low productivity and yield. In this work, the foaming properties of broth samples taken along rhamnolipid fermentation were examined. These samples had different rhamnolipid concentrations, cell concentrations, and vegetable oil contents. The results of this study showed that, at least for the P. aeruginosa E0340, the cells themselves were the most important foaming factor. The results also indicated that the presence of sufficient contents of oil and the use of low enough pH (5.5 or 5) were helpful for controlling foaming. Another apparent factor for regulating foaming was the dissolved oxygen concentration (DO). The effects of three DO levels (5%, 10% and 30%) on cell growth and rhamnolipid productivity were next investigated. The DO 10% was selected as the optimum DO level in terms of foaming, cell growth and rhamnolipid productivity. The use of soybean oil versus glycerol as carbon source was also compared for the foaming tendency, cell growth, and rhamnolipid production in the fermentation and soybean oil was selected as the optimum carbon source for this process. The rhamnolipid fermentation was then performed at different pH values to investigate if the lower pH would affect cell growth and/or rhamnolipid productivity. The optimum pH in terms of foaming and cell growth was identified at 5.7. Under the optimized conditions of DO 10%, pH 5.7 and soybean oil as the carbon source, up to 48 g/l rhamnolipids with 47% yield and maximum volumetric productivity of 221 mg/l.h was achieved. Next, the fed-batch fermentation by replacement of broth with the fresh media was developed, to extend the duration of high rhamnolipid production. And a separation/purification procedure was developed which is based on addition of 3:1 (v/v) ethanol to the cell free supernatant to separate the impurities, following by pH adjustment. By this procedure, 80% purity and 80% recovery of rhamnolipids was achieved. Finally, as an example of potential applications of rhamnolipids, in this work it has been shown that rhamnolipids, at 10 and 200 mg/l, significantly reduced the initial attachments of the Gram negative E. coli, P. putida and P. aeruginosa and the Gram positive B. subtilis on both hydrophilic glass and hydrophobic OTS-modified surfaces.
Lu-Kwang Ju, Dr. (Advisor)
Gang Cheng, Dr. (Committee Member)
Lingyun Liu, Dr. (Committee Member)
Ge Zhang, Dr. (Committee Member)
John Senko, Dr. (Committee Member)
Chemical Engineering
rhamnolipid; biosurfactant; Pseudomonas aeruginosa; fermentation; foam; attachment

Recommended Citations

Citations

  • Sodagari, M. (2013). Optimization of Production and Recovery of Rhamnolipids and Study of Their Effect on Bacterial Attachment [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1385081228

    APA Style (7th edition)

  • Sodagari, Maysam. Optimization of Production and Recovery of Rhamnolipids and Study of Their Effect on Bacterial Attachment . 2013. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1385081228.

    MLA Style (8th edition)

  • Sodagari, Maysam. "Optimization of Production and Recovery of Rhamnolipids and Study of Their Effect on Bacterial Attachment ." Doctoral dissertation, University of Akron, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1385081228

    Chicago Manual of Style (17th edition)

akron1385081228
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This open access ETD is published by University of Akron and OhioLINK.