Decontamination strategies and enzyme dosages for the fermentation of food waste to produce ethanol

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dc.contributor.advisorVan Rensburg, Eugeneen_ZA
dc.contributor.advisorGörgens, Johann Ferdinanden_ZA
dc.contributor.advisorCoetzee, Gerhardten_ZA
dc.contributor.authorvan Rooyen, Jaybeen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.en_ZA
dc.date.accessioned2024-03-05T10:09:59Zen_ZA
dc.date.accessioned2024-04-26T22:44:58Zen_ZA
dc.date.available2024-03-05T10:09:59Zen_ZA
dc.date.available2024-04-26T22:44:58Zen_ZA
dc.date.issued2024-03en_ZA
dc.descriptionThesis (MEng)--Stellenbosch University, 2024. en_ZA
dc.description.abstractENGLISH ABSTRACT: Innovative solutions are required to deal with an ever-increasing energy demand and generation of organic waste. Processes where energy or valuable chemicals can be produced from waste, will support the circular economy and a sustainable future. Ethanol production from biomass, such as maize or sugar cane, is a mature technology. However, ethanol production from food waste (FW) is far more challenging, given variable feed composition and microbial contamination. This research aimed to produce ethanol from food waste by evaluating (i) different decontamination strategies, (ii) different yeast strains, namely Saccharomyces cerevisiae Ethanol Red® and S. cerevisiae ER T12, which is an advanced strain engineered to secrete α-amylase, and (iii) increasing solids loading to produce higher ethanol concentrations. Ethanol fermentation using pre- and post-consumer FW was conducted in shake flasks at 30 °C for 72 h. Thermal sterilisation proved effective for post-consumer FW at a low liquefaction temperature of 55 °C with a significant (p < 0.05) increase in ethanol yield of 77.79% compared to 67.29% recorded after fermentation using an unsterilised feed. Similarly, at a liquefaction temperature of 55 °C after thermal sterilisation of pre-consumer FW, an ethanol yield of 92.2% was obtained, substantially higher than the 48.2% yield of the control where the feedstock remained unsterilised. This data suggested that thermal sterilisation effectively served simultaneously as a decontamination and gelatinisation strategy. Substantial decreases in enzyme dosages of up to 33% were achieved by using the consolidated bioprocessing (CBP) yeast S. cerevisiae ER T12 without affecting the ethanol yield of 80.87% ± 1.40 and productivity 1.51 g/L/h compared to 82.56% ± 2.81 and 1.54 g/L/h when using S. cerevisiae strain Ethanol Red as benchmark. The same enzyme reduction of https://scholar.sun.ac.za iii | P a g e 33% was observed for the post-consumer FW. The ethanol concentration of the pre-and postconsumer FW was increased by 96% to 74.11 ± 0.75 g/L and 85% to 48.52 ± 1.32 g/L without a significant effect on the ethanol yield when the solids loading was increased to 20.6% and 21.06% w/v. Although sterilisation proved to be an effective decontamination method, it remains energy intensive, which could affect the process's financial feasibility. Using the CBP yeast can substantially decrease operational costs due to the reduced requirements for commercial enzymes, which is crucialto developing a sustainable FW fermentation process. The CBP yeast strain proved effective even when the solids loading was increased, and the results are promising, showing that the usage of CBP yeasts can further improve the viability of the fermentations.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.af_ZA
dc.description.versionMastersen_ZA
dc.format.extent114 pagesen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130579en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subjectFood waste; Bioethanol; Decontamination; Consolidated bioprocessing (CBP)en_ZA
dc.subject.lcshEthanol as fuelen_ZA
dc.subject.lcshWaste products as fuelen_ZA
dc.subject.lcshCircular economyen_ZA
dc.subject.lcshFood wasteen_ZA
dc.subject.lcshDecontamination (from gases, chemicals, etc.)en_ZA
dc.subject.lcshFeeds -- Contaminationen_ZA
dc.subject.lcshMicrobial contaminationen_ZA
dc.subject.lcshFermentation products industryen_ZA
dc.titleDecontamination strategies and enzyme dosages for the fermentation of food waste to produce ethanolen_ZA
dc.typeThesisen_ZA
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