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Process development for in-situ production and recovery of lipopeptides
Thesis (PhD)--Stellenbosch University, 2024.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613841796366336 |
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| access_status_str | Open Access |
| author | Van Niekerk, Kirsten Jacobus |
| author2 | Pott, Robert William McClelland |
| author_browse | Pott, Robert William McClelland Van Niekerk, Kirsten Jacobus |
| author_facet | Pott, Robert William McClelland Van Niekerk, Kirsten Jacobus |
| author_sort | Van Niekerk, Kirsten Jacobus |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description |
Thesis (PhD)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131959 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:42:33.557Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131959 Process development for in-situ production and recovery of lipopeptides Van Niekerk, Kirsten Jacobus Pott, Robert William McClelland Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Biosurfactants Fermentation Lipopeptides UCTD Thesis (PhD)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Lipopeptides have gained attention in the bioremediation, pharmaceutical, food, and personal care sectors. The agricultural industry also stands to gain significant benefits and possible advancements, as these molecules can be used as an environmentally friendly and non-toxic biocontrol alternative to synthetic chemicals used as antifungal agents. Furthermore, lipopeptides can offer a solution to resistant pathogens, as they have a different mode of action. The widespread adoption of lipopeptides is, however, hindered by comparatively high production costs, exacerbated by the producing organism's capacity to re-metabolize the product under nutrient-limiting conditions. Further, depending on the application, lipopeptide mixtures may require some purification. The use of an aqueous two-phase system (ATPS) is investigated as an effective method for producing and separating lipopeptides. Glycerol proved to be the optimal carbon source for B. circulans cultivation, reaching concentrations of 13.3 g.L⁻¹ cell dry weight. Fructose promoted lipopeptide production with concentrations of 69.93, 111.83 and 35.45 mg.L⁻¹ of iturin, fengycin and surfactin. However, B. amyloliquefaciens cultivated on glucose produced higher concentrations of lipopeptides, while being generally regarded as safe (GRAS status), and on that basis was selected as an appropriate strain. This work found F. euwallaceae to be strongly affected by lipopeptides produced by B. amyloliquefaciens. Specifically, iturin and fengycin were demonstrated to be effective antifungal agents, whereas surfactin showed no inhibitory effect on the growth of F. euwallaceae. A lipopeptide mixture of 1.5 g.L⁻¹ (47% surfactin, 21% iturin and 32% fengycin) was seen to reduce the biomass of F. euwallaceae from 5 to 1 g.L⁻¹, with an LD50 of 1.1 mg.L⁻¹ at day 5. Phase behaviour, in ATP systems, is highly influenced by physical and chemical properties, which can be altered by surfactants. This study found that the addition of surfactants will push the phase envelope away from the origin, and demonstrated for the first time the impact of various surfactants on ATPS phase formation. The effect was more prominent at high salt and low polymer concentrations. Extractions in the presence of surfactants may need to utilise updated phase diagrams, in order to properly operate the separation system. B. amyloliquefaciens growth and lipopeptide production were investigated under ATPS conditions. In the phosphate ATPS, iturin partitioned primarily to the polymer phase with concentrations up to 267 mg.L⁻ ¹, while the fengycin primarily partitioned to the salt phase with concentrations of 118 mg.L⁻¹. Surfactin was found to accumulate in the solid phase under ATPS conditions. This study explores the use of aqueous two-phase systems as a separation and purification method for lipopeptides. Three salts, with phosphate, sulphate, or tartrate anion groups, with PEG 2000, 6000 or 10000, were evaluated to determine the phase-composition effect on lipopeptide partitioning. This work demonstrated that a phosphate/PEG 2000 system can be an effective tool at separating iturin, fengycin and surfactin together from spent media and cells. Furthermore, a phosphate/PEG 6000 system can be used to concentrate the two antifungal lipopeptides (iturin and fengycin). Sulphate/PEG 2000, sulphate/PEG 6000 and tartrate/PEG 2000 systems successfully forced iturin to partition to the top polymer-rich phase, away from other lipopeptides. This study evaluated the oxygen transfer coefficient (KLa), overall oxygen solubility (C*), and oxygen transfer rate (OTR) in a ATPS at different air flow rates, top- and bottom-phase ratios, and agitation speeds in order to characterise the oxygen transfer in ATPS systems when implemented in bioreactors. It was found that KLa is higher for each ATPS when compared to pure water, however the saturation concentration of oxygen was significantly decreased. Scaling the in-situ production to a bioreactor, the study found that maximum biomass concentration was reduced from 6.1 g.L⁻¹ in standard media to 5.5 g.L⁻¹ under ATPS conditions. Lipopeptide concentrations increased over time under ATPS conditions, indicating a successful barrier between product and cells. Iturin partitioned to the polymer-rich phase in concentrations up to 156 mg.L⁻¹ with fengycin at 28 mg.L⁻¹. Surfactin was found to precipitate out of solution. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-05-02T07:20:33Z 2025-05-02T07:20:33Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131959 Stellenbosch University xvi, 197 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Biosurfactants Fermentation Lipopeptides UCTD Van Niekerk, Kirsten Jacobus Process development for in-situ production and recovery of lipopeptides |
| title | Process development for in-situ production and recovery of lipopeptides |
| title_full | Process development for in-situ production and recovery of lipopeptides |
| title_fullStr | Process development for in-situ production and recovery of lipopeptides |
| title_full_unstemmed | Process development for in-situ production and recovery of lipopeptides |
| title_short | Process development for in-situ production and recovery of lipopeptides |
| title_sort | process development for in situ production and recovery of lipopeptides |
| topic | Biosurfactants Fermentation Lipopeptides UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131959 |
| work_keys_str_mv | AT vanniekerkkirstenjacobus processdevelopmentforinsituproductionandrecoveryoflipopeptides |