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The enzymatic valorisation of technical lignins from different sources to phenols
Thesis (PhD)--Stellenbosch University, 2021
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2021
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| _version_ | 1867613845978087424 |
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| access_status_str | Open Access |
| author | Majeke, Bongo Mount-Batten |
| author2 | Gorgens, Johann F. |
| author_browse | Gorgens, Johann F. Majeke, Bongo Mount-Batten |
| author_facet | Gorgens, Johann F. Majeke, Bongo Mount-Batten |
| author_sort | Majeke, Bongo Mount-Batten |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2021 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/110515 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:42:37.450Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2021 |
| publishDateRange | 2021 |
| publishDateSort | 2021 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/110515 The enzymatic valorisation of technical lignins from different sources to phenols Majeke, Bongo Mount-Batten Gorgens, Johann F. Tyhoda, Luvuyo Stellenbosch University. Faculty of Engineering. Dept. of Process engineering. Phenolic monomers UCTD Lignin -- Peroxidase Quinone reductase Thesis (PhD)--Stellenbosch University, 2021 ENGLISH ABSTRACT: Next to cellulose, lignin is the second most abundant natural polymer in the world. Commercially, it is generated as a by-product of the paper and pulp industry and emerging cellulosic ethanol processes. Both industries mainly incinerate lignin to complement their energy requirements, thereby underutilising this valuable renewable resource. The phenolic nature of lignin makes it attractive for the sustainable production of high-value chemicals. Efficient valorisation of lignin requires its depolymerisation to monomeric phenols. Over the years, several lignin depolymerisation strategies have been developed, and this study mainly focused on the enzymatic approach, which offers advantages such as high product selectivity and environmental friendliness. Among the targeted enzymes was the so-called lignin peroxidase (LiP) based on its ability to oxidise both phenolic and non- phenolic lignin moieties. Before the exploitation of the LiP enzyme, the first objective was to resolve barriers associated with its efficient production through the bioreactor optimisation of a methanol fed- batch culture using a recombinant strain of the methylotrophic yeast Pichia pastoris. The maximum volumetric activity, protein concentration, and specific activity of the LiP enzyme were 4480 U/L, 417 mg/L, and 10.7 U/mg, respectively. Upon the application of LiP to the selected technical lignins, the enzyme preferentially catalysed lignin re-polymerisation, with minimal depolymerisation activity, which is a common characteristic of most enzymes involved in lignin modification. To overcome this catalytic promiscuity, and promote lignin depolymerisation, which is desirable for producing phenolic monomers, quinone reductase (QR) enzyme was produced to work cooperatively with LiP (Objective 2). The synergistic application of LiP and QR enzymes achieved the desired lignin depolymerisation and thereby reduced the molecular weight (MWs) of soda-anthraquinone (SAQ) lignin, steam explosion (S-E) lignin, and two sulphite lignins (NaE and NaPE) by 31%, 41%, 34%, and 52%, respectively. However, the desired monomeric phenols from the catalytic activity of the enzyme cocktail (LiP and QR) were still below the quantifiable limit in terms of mass yields. Therefore, enzymatic pre-treatment of lignins followed by pyrolysis was applied to improve the production of monomeric phenol yields (Objective 3). Among the selected lignins, SAQ produced the highest total phenols at 7.84 wt.%, which was within the range (4.59-8.23 wt.%) of pyrolysis catalysed in the presence of inorganic chemicals, applied to a similar lignin. AFRIKAANSE OPSOMMING: Naas sellulose, is lignien die tweede volopste natuurlike polimeer ter wêreld. Kommersieel word dit gegenereer as ’n by-produk van die papier-en-pulp-industrie en opkomende sellulosiese etanolprosesse. Beide industrieë verbrand hoofsaaklik lignien om hul energievereistes te komplimenteer, en daardeur onder-gebruik hulle hierdie waardevolle herwinbare bron. Die fenoliese natuur van lignien maak dit aantreklik vir die volhoubare produksie van hoë-waarde chemikalieë. Doeltreffende valorisasie van lignien vereis sy depolimerisering na monomeriese fenole. Oor die jare is verskeie lignien- depolimeriseringstrategieë ontwikkel, en hierdie studie fokus hoofsaaklik op die ensimatiese benadering, wat voordele inhou soos hoë produkselektiwiteit en omgewingsvriendelikheid. Onder die geteikende ensieme was die sogenaamde lignien peroksidase (LiP) gebaseer op sy vermoë om beide fenoliese en nie-fenoliese lignienhelftes te oksideer. Voor die eksploitasie van die LiP-ensiem, was die eerste doel om beperkinge geassosieer met sy doeltreffende produksie op te los deur die bioreaktor optimering van ’n metanolvoerlotkultuur deur ’n rekombinante lyn van Pichia pastoris te gebruik. Die maksimum volumetriese aktiwiteit, proteïenkonsentrasie, en spesifieke aktiwiteit van die LiP-ensiem was 4480 U/L, 417 mg/L, en 10.7 U/mg, onderskeidelik, en hierdie hoeveelhede was veel hoër as dié bereik in vorige studies. Met die toepassing van LiP op die geselekteerde tegniese lignien, het die ensiem die lignien-herpolimerisering voorkeurend gekataliseer, met minimum depolimeriseringsaktiwiteit, wat ’n algemene karaktertrek is van die ensieme betrokke in lignienmodifikasie (bv. lakase). Om hierdie katalitiese verwarring te oorkom, en lignien- depolimerisering te bevorder, wat wenslik is vir produksie van fenoliese monomere, was die kinoonreduktase (QR) -ensiem geproduseer om in samewerking met LiP te tree (Doel 2). Die sinergistiese toepassing van LiP- en QR-ensieme het die gewenste lignien depolimerisering bereik en daardeur die molekulêre gewig (MWs) van soda-antrakinoon (SAQ) -lignien, stoomontploffing (S-E) - lignien, en twee sulfietlignien (NaE en NaPE) met 31%, 41%, 34% en 52%, onderskeidelik, verminder. Die gewenste monomeriese fenole van die katalitiese werking van die ensiemmengsel (LiP en QR) was egter steeds onder die kwantifiseerbare limiet in terme van massa-opbrengs. Daarom was ensimatiese voorbehandeling van lignien gevolg deur pirolise toegepas om die produksie van monomeriese fenolopbrengste te verbeter (Doel 3). Onder die behandelde lignien, het SAQ die hoogste totale fenole geproduseer by 7.84 wt.% droë lignien, wat hoër was as pirolise gekataliseer met anorganiese materiaal, toegepas op soortgelyke lignien. Doctoral 2021-05-31T09:14:47Z 2021-05-31T09:14:47Z 2021-03 Thesis http://hdl.handle.net/10019.1/110515 en_ZA Stellenbosch University 155 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Phenolic monomers UCTD Lignin -- Peroxidase Quinone reductase Majeke, Bongo Mount-Batten The enzymatic valorisation of technical lignins from different sources to phenols |
| title | The enzymatic valorisation of technical lignins from different sources to phenols |
| title_full | The enzymatic valorisation of technical lignins from different sources to phenols |
| title_fullStr | The enzymatic valorisation of technical lignins from different sources to phenols |
| title_full_unstemmed | The enzymatic valorisation of technical lignins from different sources to phenols |
| title_short | The enzymatic valorisation of technical lignins from different sources to phenols |
| title_sort | enzymatic valorisation of technical lignins from different sources to phenols |
| topic | Phenolic monomers UCTD Lignin -- Peroxidase Quinone reductase |
| url | http://hdl.handle.net/10019.1/110515 |
| work_keys_str_mv | AT majekebongomountbatten theenzymaticvalorisationoftechnicalligninsfromdifferentsourcestophenols AT majekebongomountbatten enzymaticvalorisationoftechnicalligninsfromdifferentsourcestophenols |