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Lactic Acid Recovery of Brewers' Spent Grain / submitted by Theresa Kaltenbrunner
AuthorKaltenbrunner, Theresa
CensorPaulik, Christian
PublishedLinz, 2018
DescriptionIV, 48 Blätter : Illustrationen
Institutional NoteUniversität Linz, Masterarbeit, 2018
Document typeMaster Thesis
Keywords (EN)lactic acid / brewers' spent grain / enzymatic hydrolysis / lactic acid fermentation
URNurn:nbn:at:at-ubl:1-23521 Persistent Identifier (URN)
 The work is publicly available
Lactic Acid Recovery of Brewers' Spent Grain [2.49 mb]
Abstract (English)

The aim of this master thesis was the recovery of lactic acid of the starchy lignocellulosic biomass, brewers spent grain. Since brewers spent grain is the major by-product in the brewing industry, it is lignocellulosic waste, which is available in high quantities, for the conversion into added valuable components. At the beginning of this work, the composition of the brewers spent grain provided from the brewery of the Institute for Chemical Technology for Organic Materials was analysed. More specifically, the ash, protein, fat, dry, carbohydrate, acid soluble and acid insoluble lignin content were determined. The carbohydrates were investigated more accurately concerning their poly- and monosaccharide content. In order to enhance the accessibility of the polysaccharides to the enzymes, the brewers spent grain was pre-treated via the physicochemical process, steam explosion. Different conditions were selected for these experiments and to determine the impact of the conditions on the pre treated material, it was characterised like the initial brewers spent grain. Furthermore, an enzymatic hydrolysis was executed in order to receive fermentable sugars. Therefore, an enzyme mix was prepared regarding the composition of the polysaccharides. To optimise this process, an experiment was planned with the program Design Experts concerning the factors dry content, pH-value, temperature, enzyme concentration and severity factor (condition of the pre-treatment). The degree of hydrolysis after 72 h, quantified via high-performance liquid chromatography, was chosen as the response. The design of experiments was evaluated for the three main monosaccharides in brewers spent grain, glucose, xylose and arabinose. In the last part of this thesis, the lactic acid bacterial strain Lactobacillus delbrueckii subsp. delbrueckii was characterised with regard to the conversion of different C-sources and the effect on the specific growth rate. Additionally, a fermentation was carried out with the received beer hydrolysate of an enzymatic hydrolysis under optimised conditions. Another part of the characterisation of the strain was the investigation of the fermented lactic acid concerning its optical rotation via polarimetry.

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