Browsing by Author "Du Toit, Lorinda"

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    Triticale grain fermentation for production of bio ethanol and animal feed
    (Stellenbosch : Stellenbosch University, 2019-04) Du Toit, Lorinda; Gorgens, Johann F.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: High quantity of starch and relative high protein content, compared to other cereal grains, make triticale ideal as a feedstock for production of bioethanol and animal feed. It is mostly planted as feed for livestock and ground cover, therefore (if planted on marginal lands) no competition exists with the human food industry, as is the case when maize or wheat is used for bioethanol production. The conventionally applied warm conversion process of starch to ethanol, requires high heat energy inputs, thus increasing the cost of production. The lesser used cold conversion process requires less heat energy, but a higher enzyme dosage is required to achieve similar conversion efficiencies and ethanol yields. Therefore, reduction in enzyme dosage in conjunction with lower energy requirements will decrease operation costs for the cold conversion process, possibly increasing profitability. The main aim of this study was to optimise four process configurations, using whole-milled and debranned-milled triticale grains as feedstock for the conventional warm and cold conversion processes, in an effort to reduce the enzyme dosage required to achieve industry standards for fermentation performance (above 90% of the theoretical maximum yield). The next step was to scale up all process configurations and determine which configuration yields the best quality distiller’s dried grains with solubles (in terms of protein and fibre content) while maintaining industry standards for fermentation performance. A central composite design (CCD), with enzyme dosage and hydrolysis time as independent variables, was used and experiments were carried out in 250 mL flasks. Fermentation performance was measured in terms of ethanol concentration, ethanol yield and ethanol productivity. Statistical models, relating independent variables and optimal performance measures, were developed. The models were validated in 5 L and 100 L scale-up experiments. The quality of distiller’s dried grains with solubles (DDGS) produced from the scaled-up experiments were measured an compared across all process configurations and to canola oil cake and soy protein. Of the 100 L scaled-up experiments, the warm debranned configuration performed best with a final ethanol yield (as a % of the theoretical maximum) of 94.2%. The cold debranned configuration and warm whole-milled configuration came second and third, with 92.1% and 90.3% respectively. The cold whole-milled configuration did not reach the benchmark of 90% yield. Productivities for warm whole-milled and debranned grains were 1.7 and 2.5 g/L/h respectively, while cold whole-milled and debranned configurations achieved 1.4 and 2.2 g/L/h. Debranning of grains had a significant (p<0.05) positive effect on both fermentation performance and quality of DDGS of the warm and cold processes. Moreover, DDGS produced from the cold debranned configuration had the highest quality. With a 44% crude protein and 13.85% acid detergent fibre content, it is ideal as a high-protein animal feed for monogastric animals.