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Process optimization for rhamnolipids production and their environmental impacts

Invally, Krutika Ravi
http://orcid.org/0000-0002-4407-1121
http://rave.ohiolink.edu/etdc/view?acc_num=akron1541755267451868

Abstract Details

2018, Doctor of Philosophy, University of Akron, Chemical Engineering.
Rhamnolipids are biosurfactants produced mainly by Pseudomonas aeruginosa. Rhamnolipids have several promising environmental, agricultural, and industrial applications. The commercial realization of many of these applications requires an acceptable process economics for rhamnolipids production. The main goal of this project was to improve the synthesis process to obtain high yield and productivity, which would enable its utilization in different applications. The project was divided into three main parts. The first part focused on improving the rhamnolipid production process by optimizing the upstream fermentation process as well as the downstream purification process. The second part evaluated application of rhamnolipids as corrosion inhibitors to prevent biofilm formation by sulfate reducing bacteria which are the main perpetrators of microbiologically influenced corrosion in steel. The third part of the project assessed the biolytic properties, as a component of ecological effects, of rhamnolipids. There are three main challenges in rhamnolipids production- low productivity, high foaming, and expensive downstream processing. Previously, it was found that in a typical batch fermentation, there was significant decrease in rhamnolipids productivity beyond a certain period due to long-term maintenance of the culture in nitrogen-limited conditions. The rhamnolipid production in long fermentation runs can be reinstated by addition of nitrogen-containing fresh medium in a fed-batch setup. However, the results from the current study showed that periodic addition of nitrogen source to a nitrogen-limited culture medium resulted in a controlled cell growth phase which led to lower specific productivity of rhamnolipid. To overcome this limitation, fed-batch fermentation runs with periodic N-source supplementation were conducted under non-nitrogen limited conditions to maintain the culture in stationary phase throughout the run. A fermentation design with two-staged growth was devised to prevent excessive foaming at high cell concentrations and obtain high rhamnolipid productivity. Furthermore, rhamnolipids production under anaerobic denitrifying conditions was investigated to overcome the problem of foaming, which is associated with aerobic fermentations. Encapsulation strategies were developed using solid carbon substrates such as waste grease and lard to deliver nitrate ions in a controlled-release mode during anaerobic fermentations. Studies were also conducted to improve the purification step of rhamnolipids by tracking rhamnolipids mass going through different unit operations in the existing downstream process. An additional step of biopolymer removal using alcohol precipitation was recommended prior to the acid precipitation step for isolation of rhamnolipids. Finally, the mechanisms for lytic effect of rhamnolipid on living cells and its impact on aquatic organisms and ecosystems were determined. Rhamnolipids were found to have less biolytic activity than a commonly used surfactant, sodium dodecyl sulfate, and were significantly slower in exerting the effect on living cells.
Lu-Kwang Ju, Dr. (Advisor)
Bi-min Zhang Newby, Dr. (Committee Member)
Chelsea Monty-Bromer, Dr. (Committee Member)
Teresa Cutright, Dr. (Committee Member)
John Senko, Dr. (Committee Member)
355 p.
Biochemistry; Chemical Engineering
Rhamnolipids; biosurfactants; fermentation; Pseudomonas aeruginosa; biolysis;

Recommended Citations

Citations

  • Invally, K. R. (2018). Process optimization for rhamnolipids production and their environmental impacts [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1541755267451868

    APA Style (7th edition)

  • Invally, Krutika. Process optimization for rhamnolipids production and their environmental impacts . 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1541755267451868.

    MLA Style (8th edition)

  • Invally, Krutika. "Process optimization for rhamnolipids production and their environmental impacts ." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1541755267451868

    Chicago Manual of Style (17th edition)

akron1541755267451868
306
© 2018, some rights reserved.Creative Commons License Process optimization for rhamnolipids production and their environmental impacts by Krutika Ravi Invally is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Akron and OhioLINK.