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Development of a bubble column bioprocess for the application of alkane bioactivation
Thsesis (PhD) -- Stellenbosch University, 2022
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867613830787366912 |
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| access_status_str | Open Access |
| author | Abufalgha, Ayman |
| author2 | Pott, Robert William M. |
| author_browse | Abufalgha, Ayman Pott, Robert William M. |
| author_facet | Pott, Robert William M. Abufalgha, Ayman |
| author_sort | Abufalgha, Ayman |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thsesis (PhD) -- Stellenbosch University, 2022 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/126170 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:42:21.587Z |
| license_str | Other โ see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar โ Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar โ Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/126170 Development of a bubble column bioprocess for the application of alkane bioactivation Abufalgha, Ayman Pott, Robert William M. Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering. Alkanes Bubble column reactors Biochemical engineering UCTD Thsesis (PhD) -- Stellenbosch University, 2022 ENGLISH ABSTRACT: Hydrocarbon upgrading has become an important field worldwide, and particularly in South African industries, due to the significant hydrocarbon resources, especially in the form of coal. An attractive method of upgrading these hydrocarbons to high-value products is through biological activation processes, whereby an oxygen moiety is inserted into the hydrocarbon backbone by microbes. However, this process is affected by several factors such as oxygen availability, bioreactor geometry, and the activity of the organism. Therefore, this work has investigated a bubble column hydrocarbon bioprocess through examining the hydrodynamics and oxygen transfer in multiphase systems under a range of operating conditions, such as hydrocarbon concentration (๐ป๐ถ), superficial gas velocity (๐๐บ) and solids (deactivated yeast, cornflour, and wildtype hydrocarbon-degrader (Alcanivorax borkumensis SK2)) loading (๐๐ฟ). Furthermore, this work explored the genetic modification of Alcanivorax borkumensis SK2 in order to convert n-alkanes to their alcohol as bioproducts, using the native pathway. Objective 1 examined the hydrodynamics (gas holdup and bubble size) in an air-deionized water-deactivated yeast-hydrocarbons system. It was observed that bubble size and gas holdup increased with increasing UG (1 to 3 cm.s-1), due to the increase in the number of bubbles in the system. whereas an increase in SL (0.5 to 6 g/l) resulted in bubble size increasing, which thereafter caused a decrease of gas holdup in a bubble column reactor (BCR). Yeast addition was found to change the fluid surface tension and viscosity and therefore affected the system hydrodynamics. Objective 2 studied volumetric oxygen transfer coefficient (KLa) in different phases i) air-deionized water, ii) air-deionized water-deactivated yeast, iii) air-deionized water-hydrocarbons, and iv) air- deionized water-deactivated yeast -hydrocarbons in BCR. It was found that KLa was affected differently by each phase system. E.g., KLa increased with increasing UG in all phase systems due to an increase in the number of small bubbles which enhanced gas holdup. Whereas the addition of yeast and hydrocarbons reduced KLa due to increases in the bubble size. In air- deionized water -hydrocarbon-cornflour system (Objective 3), SL and HC affected KLa differently, whereas UG had the most significant effect on KLa and oxygen transfer area. KLa showed an optimal level at SL of 3 g/l, but any further increase resulted in a reduction in KLa. HC had shown an insignificant change in KLa with the range considered (2.5 to 20%v/v). This was a result of changing hydrodynamic conditions, which affected the mass transfer coefficient (KL) behaviour, as there was no corresponding change to the interfacial area. After completion of the first three objectives, it was important for Objective 4 to investigate the effect of SK2 (as a novel biomass) as the solid phase on hydrodynamics of bubble column hydrocarbon bioprocess. It was observed that gas holdup increased linearly with increasing UG from 1 to 3 cm.s-1. Further, SK2 addition resulted in a reduction in fluid surface tension and therefore gas holdup was increased in air-deionized water-SK2 biomass system. Objective 5 detailed the genetic engineering of the SK2 strain by the removal of the alcohol dehydrogenase gene, alkJ1, using a gene knockout technique, with the aim of allowing accumulation of alcohol intermediates. Marked mutants of the alkJ1 gene knockout of SK2 were constructed by insertion of antibiotic resistance cassettes, with alkJ1 flanking regions. It was found that no alcohols were accumulated during the cultivation of modified SK2 in n-octane (10%, 20% and 50%) at 370C and 150 rpm for 30 days of cultivation. This finding suggested that the alkJ1 mutant of SK2 was not suitable for the bioconversion process, and that a second mutation in the alkJ2 gene of SK2 or/and a double mutant of both alkJ1 and alkJ2 may be required in order to remove the alcohol conversion step. AFRIKAANS OPSOMMING: Koolwaterstofopgradering het wรชreldwyd โn belangrike veld geword, spesifiek in Suid-Afrikaanse industrieรซ as gevolg van die beduidende koolwaterstofhulpbronne, veral in die vorm van steenkool. ล Aanloklike metode van koolwaterstofopgradering na hoรซ-waarde produkte is deur biologiese aktiveringsprosesse, waar โn suurstofgedeelte in die koolwaterstofruggraat ingesit word deur mikrobes. Hierdie proses word egter deur verskeie faktore soos suurstofbeskikbaarheid, bioreaktorgeometrie, en die aktiwiteit van die organisme, geaffekteer. Daarom het hierdie werk โn borrelkolomkoolwaterstofbioproses ondersoek deur die hidrodinamika en suurstofoordrag in multifase sisteme onder โn reeks bedryfskondisies te ondersoek, soos koolwaterstofkonsentrasie (๐ป๐ถ), oppervlakkige gassnelheid (๐๐บ) en vastestowwe (gedeaktiveerde gis, mielieblom, en wildtipe koolwaterstofdegradeerder (Alcanivorax borkumensis SK2)) lading (๐๐ฟ). Verder het hierdie werk die genetiese modifikasie van Alcanivorax borkumensis SK2 verken om n-alkane na hul alkohol om te sit as bioprodukte, deur die inheemse roete te gebruik. Doelwit 1 het die hidrodinamika (gasvasvanging en borrelgrootte) in โn lug-water-gis-koolwaterstofsisteem ondersoek. Dit is waargeneem dat borrelgrootte en gasvasvanging verhoog het met die verhoging van ๐๐บ (1 tot 3 cm.s-1) as gevolg van die aantal borrels in die sisteem, waar โn verhoging in ๐๐ฟ (0.5 tot 6 g/l) borrelgrootte-verhoging tot gevolg gehad het, wat daarna โn afname van gasvasvanging in BCR veroorsaak het. Gisbyvoeging is gevind om die vloeistofoppervlakspanning en viskositeit te verander en daarom die hidrodinamika van die sisteem te affekteer. Doelwit 2 het die suurstofoordragkoรซffisiรซnt (๐พ๐ฟa) in verskillende fases bestudeer: i) lug-water, ii) lug-water-gis, iii) lug-water-hidrokoolstowwe, en iv) lug-water-gis-hidrokoolstowwe in BCR. Dis gevind dat ๐พ๐ฟa verskillend geaffekteer is deur elke fasesisteem. Bv. ๐พ๐ฟa het verhoog met die verhoging van ๐๐บ in alle fasesisteme as gevolg van die aantal klein borrels wat gasvasvanging vergroot het. Die byvoeging van gis en hidrokoolstowwe het ๐พ๐ฟa verminder as gevolg van die verhoging in die borrelgrootte. In lug-water-koolwaterstof-mielieblomsisteem (Doelwit 3), het ๐๐ฟ en ๐ป๐ถ ๐พ๐ฟa verskillend geaffekteer, waar ๐๐บ die mees beduidende effek op ๐พ๐ฟa en suurstofoordragarea gehad het. ๐พ๐ฟa het optimale vlak by ๐๐ฟ van 3 g/l getoon, maar enige verdere verhoging het in โn afname in ๐พ๐ฟa geresulteer. ๐ป๐ถ het โn onbeduidende verandering in ๐พ๐ฟa getoon met die bestek oorweeg (2.5 tot 20%v/v). Hierdie was as gevolg van veranderende hidrodinamiese kondisies, wat die ๐พ๐ฟ-gedrag geaffekteer het, omdat daar geen ooreenstemmende verandering in die tussenvlakarea was nie. Na die voltooiing van die eerste drie doelwitte, was dit belangrik vir Doelwit 4 om die effek van SK2 (as โn nuwe biomassa) te ondersoek as die vastestoffase op hidrodinamika van borrelkolomkoolwaterstofbioprosesse. Dit is waargeneem dat gasvasvanging liniรชr verhoog het met die verhoging van ๐๐บ van 1 tot 3 cm.s-1. Verder het die byvoeging van SK2 โn afname in vloeistofoppervlakspanning tot gevolg gehad en daarom is gasvasvanging verhoog. Doelwit 5 het die genetiese modifikasie van die SK2-lyn gedetailleer deur die verwydering van die alkoholdehidrogenasegeen, alkJ l, deur โn geenuitskopstegniek te gebruik, met die doel om akkumulasie van alkoholtussenlopers toe te laat. Gemerkte mutante van die alkJ l-geen-uitskop van SK2 is gekonstrueer deur invoeging van antibiotiese weerstand kassette, met alkJ l-flankstreke. Dis gevind dat geen alkohole geakkumuleer het gedurende die kultivering van gemodifiseerde SK2 in n-oktaan (10%, 20% en 50%) by 37 ยฐC en 150 rpm vir 30 dae van kultivering nie. Hierdie bevinding stel voor dat die alkJ l-mutant van SK2 nie gepas was vir die bio-omsettingsproses nie, en dat โn tweede mutasie in die alkJ l en alkJ2 of/en ล dubbelmutant van beide alkJ I en alkJ2 vereis mag word om die alkoholomsettingstap te verwyder. Doctoral 2022-11-23T12:16:27Z 2023-01-16T12:53:40Z 2022-11-23T12:16:27Z 2023-01-16T12:53:40Z 2022-12 Thesis http://hdl.handle.net/10019.1/126170 en_ZA Stellenbosch University xxiv, 258 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Alkanes Bubble column reactors Biochemical engineering UCTD Abufalgha, Ayman Development of a bubble column bioprocess for the application of alkane bioactivation |
| title | Development of a bubble column bioprocess for the application of alkane bioactivation |
| title_full | Development of a bubble column bioprocess for the application of alkane bioactivation |
| title_fullStr | Development of a bubble column bioprocess for the application of alkane bioactivation |
| title_full_unstemmed | Development of a bubble column bioprocess for the application of alkane bioactivation |
| title_short | Development of a bubble column bioprocess for the application of alkane bioactivation |
| title_sort | development of a bubble column bioprocess for the application of alkane bioactivation |
| topic | Alkanes Bubble column reactors Biochemical engineering UCTD |
| url | http://hdl.handle.net/10019.1/126170 |
| work_keys_str_mv | AT abufalghaayman developmentofabubblecolumnbioprocessfortheapplicationofalkanebioactivation |