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Microalgae as a feedstock for ethanol production
Thesis (MSc)--Stellenbosch University, 2023.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2023
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| _version_ | 1867613972690108416 |
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| access_status_str | Open Access |
| author | De Villiers, Dewald |
| author2 | Van Zyl, Willem Heber |
| author_browse | De Villiers, Dewald Van Zyl, Willem Heber |
| author_facet | Van Zyl, Willem Heber De Villiers, Dewald |
| author_sort | De Villiers, Dewald |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2023. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/128789 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:44:38.662Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/128789 Microalgae as a feedstock for ethanol production De Villiers, Dewald Van Zyl, Willem Heber Viljoen-Bloom, Marinda Cripwell, Rosemary Anne Stellenbosch University. Faculty of Science. Dept. of Microbiology. Microalgae -- Growth Biomass energy Microalgae -- Effect of stress on Algal biofuels Microalgae -- Nitrogen content. Feedstock -- Economic aspects Chlamydomonas reinhardtii -- Effect of stress on Ethanol Chlorella sorokiniana -- Biotechnology Starch UCTD Thesis (MSc)--Stellenbosch University, 2023. ENGLISH ABSTRACT: Microalgae are increasingly considered a source for high-value products in various markets, with applications in the health food, medicinal and industrial sectors. More recently, microalgae have gained interest as a feedstock for biofuel production due to their high starch content. Various studies investigated the challenges of using microalgae in industry, such as low biomass production, complicated harvesting methods and high lipid/carbohydrate content. Although solutions and mitigation strategies have been proposed, the process must be economically feasible to compete with fossil fuels and other biofuel feedstocks. This could be achieved by optimisation of the growth conditions to maximise the biomass and starch yields and/or through enzymatic treatment to release the starch for fermentation to bioethanol. In this study, the growth conditions for two microalgal strains known for their starch - producing capabilities, Chlamydomonas reinhardtii and Chlorella sorokiniana, were optimised for enhanced biomass and starch accumulation, specifically by evaluating different carbon and nitrogen sources. The two strains were grown under mixotrophic conditions, i.e. photosynthesis in the presence of additional carbon sources (glucose and acetic acid). The C. sorokiniana strain displayed the highest biomass production (3.89 g/L) and starch accumulation (0.67 g/L) when grown in Bold Basal Media (10 g/L glucose) with a modified carbon-to-nitrogen ratio (C:N of 8:1). The C. sorokiniana strain was evaluated in a consolidated bioprocessing (CBP) process for starch-ethanol fermentation by optimising the harvest methods and pretreatment options. The study found that enzymatic pretreatment coupled with freeze-drying provided the best results. The C. sorokiniana biomass was pretreated enzymatically with pectinase and xylanase to release the internal starch granules. Consolidated bioprocessing with an amylolytic Saccharomyces cerevisiae strain (co-expressing an α-amylase and glucoamylase) yielded 4.02 g/L ethanol from a 10% microalgal substrate loading at 30°C. This study is one of only a few that observed microalgae growth in a standardised, mixotrophic growth setting where macronutrients were evaluated for optimised starch production. AFRIKAANSE OPSOMMING: Mikroalge word toenemend as ‘ʼn bron vir hoëwaardeprodukte in verskeie markte beskou, met toepassings in die gesondheidsvoedsel, medisinale en industriële sektore. Meer onlangs het mikroalge belangstelling as grondstof vir biobrandstofproduksie geniet weens hul hoë styselinhoud. Verskeie studies het die uitdagings vir die gebruik van mikroalge in die industrie ondersoek, soos lae biomassaproduksie, uitdagende oesmetodes en hoë lipied-/koolhidraat- inhoud. Alhoewel oplossings en versagtingstrategieë voorgestel is, moet die proses ekonomies lewensvatbaar wees om met fossielbrandstowwe en ander biobrandstofgrondstowwe te kompeteer. Dit kan moontlik bereik word deur optimisering van die groeitoestande om die biomassa en styselopbrengste te maksimeer, en/of deur ensiematiese behandeling om die stysel vir fermentasie na bio-etanol vry te stel. In hierdie studie is die groeitoestande vir twee mikroalgrasse bekend vir hul styselproduserende vermoëns, Chlamydomonas reinhardtii en Chlorella sorokiniana, geoptimiseer vir beter biomassa en styselakkumulasie, spesifiek deur verskillende koolstof- en stikstofbronne te evalueer. Die twee rasse is onder miksotrofiese toestande gekweek, m.a.w. fotosintese in die teenwoordigheid van addisionele koolstofbronne (glukose en asynsuur). Die C. Sorokiniana-ras het die hoogste biomassaproduksie (3,89 g/L) en styselakkumulasie (0,67 g/L) getoon wanneer dit in Bold Basal Media (10 g/L glukose) met‘'n gewysigde koolstof-tot-stikstof-verhouding (C: N van 8:1) gekweek is. Die C. sorokiniana ras is in‘'n gekonsolideerde bioverwerking (CBP) proses vir stysel-etanol fermentasie ge-evalueer deur die oesmetodes en voorbehandelingsopsies te optimiseer. Die studie het bevind dat die kombinasie van ensiematiese voorbehandeling en vriesdroging die beste resultate gelewer het. Die C. sorokiniana biomassa is ensiematies met pektinase en xilanase behandel om die interne styselkorrels vry te stel. Gekonsolideerde bioprosessering met behulp van‘'n amylolitiese Saccharomyces cerevisiae-stam (wat beide α-amilase en glukoamilase uitdruk) het 4.02 g/L etanol vanaf ʼn 10% mikroalg-substraatlading by 30°C gelewer. Hierdie studie is een van slegs 'n paar wat die groei van mikroalge in 'n gestandaardiseerde, miksotrofiese groei-omgewing waargeneem het waar makrovoedingstowwe vir geoptimiseerde styselproduksie ondersoek is. Masters 2023-07-21T12:52:46Z 2024-01-08T11:13:46Z 2023-07-21T12:52:46Z 2024-01-08T11:13:46Z 2023-12 Thesis https://scholar.sun.ac.za/handle/10019.1/128789 en_ZA en_ZA Stellenbosch University v, 64 pages : illustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Microalgae -- Growth Biomass energy Microalgae -- Effect of stress on Algal biofuels Microalgae -- Nitrogen content. Feedstock -- Economic aspects Chlamydomonas reinhardtii -- Effect of stress on Ethanol Chlorella sorokiniana -- Biotechnology Starch UCTD De Villiers, Dewald Microalgae as a feedstock for ethanol production |
| title | Microalgae as a feedstock for ethanol production |
| title_full | Microalgae as a feedstock for ethanol production |
| title_fullStr | Microalgae as a feedstock for ethanol production |
| title_full_unstemmed | Microalgae as a feedstock for ethanol production |
| title_short | Microalgae as a feedstock for ethanol production |
| title_sort | microalgae as a feedstock for ethanol production |
| topic | Microalgae -- Growth Biomass energy Microalgae -- Effect of stress on Algal biofuels Microalgae -- Nitrogen content. Feedstock -- Economic aspects Chlamydomonas reinhardtii -- Effect of stress on Ethanol Chlorella sorokiniana -- Biotechnology Starch UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/128789 |
| work_keys_str_mv | AT devilliersdewald microalgaeasafeedstockforethanolproduction |