Doctoral Degrees (Chemical Engineering)

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Browsing Doctoral Degrees (Chemical Engineering) by Subject "Amberlite IRA 900"

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    Process improvements and techno-economic analyses for the production of short-chain fructose-containing oligosaccharides from sucrose and Jerusalem artichoke tubers
    (Stellenbosch : Stellenbosch University., 2020-03) Bedzo, Oscar Koku Kplorm; Gorgens, Johann F.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: Recent years have seen significant growth in the global market for short-chain fructooligo saccharides (scFOS) and inulooligo saccharides (IOS) due to the rising health awareness and demand for calorie controlled foods. The global demand for prebiotics has been estimated at over 200000 tonnes per year, of which scFOS and IOS constitute a significant fraction. Commercial production of scFOS relies on the enzymatic polymerization of sucrose using β-fructofuranosidase, while the production of IOS relies on the controlled hydrolysis of inulin. South Africa has the potential to contribute its quota to the prebiotic market through the production of scFOS by channelling part of the sugar designated for exportation into the production of this high value product to meet the scFOS local market demand as well as contribute to the international market. Jerusalem artichoke (Helianthus tuberosus L.) tubers have inulin contents similar to that of chicory, coupled with a significant amount of protein. The ability of Jerusalem artichoke (JA) to resist pests and diseases, frost and drought coupled with its ability to grow on most soils with little fertilizer requirements, relieves it of geographical limitations and reduces cultivation expenses. With these unique properties, Jerusalem artichoke has some advantage over chicory. The co-production of IOS and protein, followed by animal feed, ethanol or biogas production from the extraction residues in a biorefinery concept, may improve the economic feasibility of IOS production from Jerusalem artichoke tubers. At present, the main source of inulin exploited for the production of IOS is the roots of chicory. However, the interesting properties of Jerusalem artichoke make it a suitable alternative source of inulin.The present study sought to improve and compare the economic feasibilities of sucrose and JA tuber as feedstocks for scFOS and IOS production respectively. This involved the minimization of scFOS production cost by exploring and optimizing the different sucrose to scFOS production scenarios (free and immobilized enzyme systems). In objectives 1-3 a novel β-fructofuranosidase responsible for scFOS production from sucrose was immobilized by adsorptionon to Amberlite IRA 900 and Dowex marathon MSAanion exchange resins and by entrapment in calcium alginate beads, in the quest to maximise the utilization of the high value enzyme.The data was implemented in objective 4 by simulating three scFOS production scenarios in Aspen Plus® v8.8 to ascertain the economic feasibility of the free and immobilized enzyme systems of scFOS production by estimating the minimum selling price (MSP) of scFOS. The scFOS production with the free enzyme system resulted in the most profitable scenario with an MSP of 2.61 $/kg compared to the set market price of 5 $/kg. The optimization of IOS production from various inulin-rich substrates obtainable from JA tubers was carried out in objective 5, with consideration of protein extraction options. The data was applied in objective 6 for the simulation of five multiproduct JA tuber biorefineries in Aspen Plus® v8.8 for IOS, protein, animal feed and bioenergyco-production, as a way of improving the economic feasibility of IOS production from JA tuber. The JA tuber biorefinery for IOS, and animal feed co-production (scenario B) was the most profitable with an MSP of 3.91 $/kg.Comparison of the best-case scenarios of scFOS and IOS productions revealed the free enzyme system of scFOS production from sucrose as the ultimately economically feasible scenario as it required lesser capital investment (15.45 M$ vs 37.82 M$) and operating expenditure (3.40 M$ vs 5.18 M$) with less technical complication than the best case of the JA tuber biorefinery scenarios. The solubility constraints associated with IOS production from the inulin in the JA tuber resulted in increased equipment sizes and utility consumption. Ultimately, the implementation of scFOS and IOS production biorefineries in South Africa would contribute to the South African economy through job creation and revenue generation.