Browsing by Author "Kossatz, Hester Lalie"

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    Evaluation of triticale straw as feedstock for the production of bioethanol in a SSF process
    (Stellenbosch : Stellenbosch University, 2014-12) Kossatz, Hester Lalie; Viljoen-Bloom, M.; Rose, Shuanita; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: The production of renewable liquid fuels such as bioethanol is currently at the forefront of scientific research, with a specific focus on production processes that are sustainable, inexpensive and environmentally friendly. Traditional biofuel feedstocks include maize, wheat, sugar and sugar beet, which can be easily converted to ethanol using hydrolytic enzymes and microorganisms. The focus has recently shifted to less expensive feedstocks, namely lignocellulosic biomass. Lignocellulose is found in all plants and byproducts or waste material from several industries can therefore be utilised for the production of lignocellulosic bioethanol, including paper sludge, wood chips, corn stover, sugarcane bagasse and straw. One of the potential alternative feedstocks for bioethanol is triticale straw. Triticale (Triticosecale rimpau) is a robust and tolerant cereal crop that is cultivated worldwide and has desirable qualities such as disease and drought tolerance and the ability to grow on marginal land. It produces grain with high protein content suitable as food or animal feed, whereas the straw has little monetary value and is therefore an ideal feedstock for bioethanol production. The straw is more susceptible to enzymatic hydrolysis than other lignocellulosic sources such as wood, sugarcane bagasse and corncobs. However, little research has been done on the enzyme activities and dosages required to utilise triticale straw as bioethanol feedstock. In this study, triticale straw was evaluated using steam-explosion pretreatment, enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) as processing pipeline. The conditions for steam-explosion were set at 203°C for 7 minutes, which improved the cellulose content of the straw by 6% and reduced the hemicellulose content by 17%. One kilogram of triticale straw produced 720 grams of water-insoluble solids (WIS), as well as a liquid fraction. Five commercial cellulase cocktails were evaluated for the hydrolysis of the WIS, with Spezyme® CP delivering the highest glucose yield (57%) at 15 FPU/g cellulose. Several strains of Saccharomyces cerevisiae were screened for their fermentative ability at 37°C and high glucose concentrations and Ethanol Red®, an industrial strain, and the wild-type strain L21 were selected for evaluation in an SSF setup. The combination of 15 FPU/g Spezyme® CP and Ethanol Red® yielded the best results on the triticale WIS, with 26.9 g/l ethanol produced after 144 hours, corresponding to 92% of the theoretical ethanol yield. The promising performance of triticale straw under laboratory conditions therefore supports further investigation on an industrial scale.