Browsing by Subject "cellulose"
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(2020)The aim of the thesis was to study enzymatic treatment as a way to modify paper grade pulp to be a suitable raw material for the future textile industry. Wood as a raw material is an environmentally friendly option for textile production but its sustainable exploitation is not easy. Currently, ionic liquids are assumed to enable a safe and sustainable process for the production of wood-based regenerated fibres. These processes commonly use dissolving pulp as their raw material but replacing dissolving pulp with a paper grade kraft pulp would decrease environmental impact and production expenses. In this work, molar mass distribution of softwood paper grade kraft pulp was selectively modified using enzymes. Enzymes were utilized instead of acids because of their favourable abilities to selectively modify targeted polymers and to increase fibre porosity. Enzymatic modifications of softwood kraft pulp were performed to decrease degree of polymerization of cellulose and lower the quantity of hemicellulose. Hydrolysis of cellulose was catalysed with endo-1,4-β-glucanase (endoglucanase) and hemicellulose was degraded using endo-1,4-β-mannanase and endo-1,4-β-xylanase. The treatments were carried out both at high (20%) and low (3%) pulp consistency to examine the synergistic effect of enzymatic and mechanical action arising in the high consistency treatment. Additionally, influence of different enzyme combinations on the pulp properties was studied. The modified pulp samples were characterized by determining intrinsic viscosity, molar mass distribution, yield loss, and its composition. The fibres were imaged with light microscopy. The degree of polymerization of the pulp cellulose was successfully decreased with a relatively small endoglucanase dose. The amount of hemicellulose was reduced by removing 11% of the total galactoglucomannan and 40% of the total arabinoglucuronoxylan. The high consistency treatments decreased intrinsic viscosity 1.9 times more on average than the low consistency treatments. The high consistency treatments were effective with low enzyme doses, easy to control, and reliably repeated. Therefore, enzymatic pulp treatment at high consistency seems to be a compatible way to modify paper grade kraft pulp to suitable raw material for textile production. Further studies related to pulp dissolution in ionic liquids, fibre spinning, and fibre regeneration should be concluded to confirm applicability of the modified fibres.
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(2019)Cellulose is a major component of plant biomass that can be used to produce bio-derived materials, chemicals, and fuels. Whereas the conversion of cellulose to chemicals and fuels is limited by the surface functionality of cellulose fibers due to their highly compact structure. A group of non-catalytic proteins including expansins, loosenins and cerato-platanins are known to alter cellulose fiber structures, presumably by breaking hydrogen bonds between cellulose microfibrils. This makes them interesting targets for the chemical and biophysical modification of plant polysaccharides. In this work, seven non-catalytic target genes were selected from the transcriptome of Phanerochaete carnosa. Pichia pastoris was transformed with expression constructs harboring the respective genes under control of the AOX1 promoter. Protein expression was analyzed by colony blot assay and small-scale expression in liquid media. Two cerato-platanins (CP1, CP4) and 3 loosenin-like proteins (LOOL7, LOOL9 and LOOL12) were successfully produced in large-scale. The identity of CP1, LOOL7, LOOL9 and LOOL12 was confirmed by MALDI-TOF MS analysis. The proteins showed no hydrolytic activity when tested on carboxymethyl cellulose, xylan or glucomannan. Defibrillation assay results of CP1, CP4, LOOL7 and LOOL9 suggested that the non-catalytic proteins lack specific weakening effect on cellulose filter paper. Considerably high protein blank absorbance of LOOL7 indicates possibility for self-assembling abilities of the protein. Incubation of filter paper with CP1 seemed to improve the hydrolytic action of cellulases on Avicel and filter paper, as shown by complementation assays. The effect of LOOLs on enzymatic cellulose hydrolysis varied over the time course of different experiments. Most notably, LOOL7 and LOOL12 were able to increase the reducing sugar release from Avicel and filter paper by cellulase at different time points. The maximum increase of cellulose conversion achieved by LOOL12 was 30% after 10 min when non-catalytic proteins and Cellic CTec2 were added simultaneously. LOOL7 showed highest conversion improvement of 21% after 6 h pre-incubation assay with filter paper. Upon prolonged pre-incubation (72 h), significant improvement of filter paper hydrolysis was noticed for CP4 and CP1, while LOOLs unable to enhance the hydrolytic activity of the tested cellulase mixture. For the first time, a comparative study of cerato-platanins and loosenin-like proteins was carried out and the findings presented in this thesis suggest that especially CP1 can be a promising accessory protein for efficient bioconversion of cellulose. Nevertheless, a deeper understanding of the structure and function of these non-catalytic proteins will be helpful in determining their potential biotechnological applications.
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(2016)The literature review dealed with fat replacers in frankfurters. Manufacturing, properties and usages of microcrystalline cellulose were described. Also other fat replacers that are at the moment in use are described, such as hydrocolloids and proteins from vegetable. The literature review also described different methods that have been used to measure properties of frankfurters. The aim of the experimental work was to find out the influence of two different types of microcrystalline cellulose, Vivapur® 105(i) and Arbocel® M80(ii), on the properties of frankfurters, and can they been used as a fat replacer. Three different concentrations of microcrystalline cellulose (MCC) (1 %, 3 % and 5 %) Were studied and compared to the control sample. Measured properties of frankfurters were pH, water holding, cooking loss, firmness and bite force. Also amount of free water was measured with NMR. Although adding MCC decreased pH of frankfurter closer to the isoelectric point, it did not affect as lowering water holding. Both MCC(i) and MCC(ii) increased significantly (p<0,05) firmness of the frankfurters when measuring was made with warm samples, excluding MCC(i) 3 % concentration. Effect was not as visible in the measurements of bite force.
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