Browsing by Author "Botha, Dewald Du Plessis"

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    Investigation into the assimilation of free amino nitrogen from bread waste during yeast proliferation
    (Stellenbosch : Stellenbosch University, 2023-12) Botha, Dewald Du Plessis; Stefan, Hayward; Strauss, Eric; Tait, Timo; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.
    ENGLISH ABSTRACT: Bread is a staple food in many economies. It is nutrient rich, cheap, and modern bakeries provide it in excess to be able to meet supply within stringent quality control parameters. Overproduction and consumer underutilisation, however, often result in accumulated bread going to waste if suitable valorisation methods are not available. Yet, unused bread is often returned to production facilities unaltered and may easily be processed to a dried commodity with a stable shelf life. Dried bread crumb is especially applicable to the agricultural industry as a feed additive, but it is also attractive in the biotechnology sector to sustain microbial growth for industrial and pharmaceutical applications. Ethanol is an attractive end-product due to its applicability in various industries, whether related to food and beverages, chemicals, or pharmaceutical sectors. This study therefore aims to establish a process to liberate sugars and free amino compounds from bread waste, relevant to alcoholic fermentation in yeast. Dried bread waste was processed enzymatically to hydrolyse polysaccharides to fermentable sugars and, following fermentation and distillation, alcohol yields of 10% alcohol by volume (ABV) was achieved. Moreover, high performance liquid chromatography coupled to UV/Vis detection was used to establish an analytical method for the quantification amino acids. Analysis of these nitrogen containing compounds revealed that a substantial amount of protein and essential amino acids are left following distillation to support a secondary fermentation. After proteolytic digestion of the dried wash, a nutrient rich mixture was obtained that promoted and supported the growth of yeast in the presence of a suitable carbohydrate source such as sucrose. This nutrient source was shown to be comparable to conventional commercial alternatives. Although the crude yeast nutrient resulted in slower exponential phase it ultimately proved to be superior in sustaining greater yeast biomass. This thesis describes the successful generation of a yeast nutrient from a bread waste product which was obtained after valorisation of bread waste in a bioethanol production process, thus creating a solution to bread waste that may with further development be waste free.