All these results advance our understanding on how stimulatory agents can be used to increase the production of useful metabolites by submerged fermentation of mushroom mycelium and indicate its potential biotechnological applications. / By use of one- and two-dimensional gels in proteomic analysis, some functional mycelial proteins that were differentially expressed by the addition of Tween 80 were identified. The up-regulation of heat shock proteins might help to maintain cellular viability under environmental stress. A down-regulation of YALI0E34793p and an up-regulation of ATP citrate lyase isoform 2 might suppress the activity of TCA cycle and subsequently stimulated the EPS production. Up-regulation of fatty acid synthase alpha subunit FasA might promote the synthesis of long-chain fatty acids and their incorporation into the mycelial cell membranes. Up-regulation of mitogen-activated protein kinase might facilitate the signal transduction in these processes. / The BPS, a highly branched glucomannan produced by the addition of Tween 80 in the fermentation broth of PTR mycelium had similar carbohydrate and protein content, monosaccharide composition and glycosidic linkages except by having a significantly lower molecular weight when compared to those of the control. Both BPS, with and without addition of Tween 80, could significantly inhibit (p < 0.05) the in vitro growth of a chronic myelogenous leukemia cells K562 in a dose dependent manner, with an estimated IC50 value of 43.7 and 47.6 microg/mL, respectively. / The effects of different kinds of stimulatory agents including fatty acids, surfactants and organic solvents were compared. The optimum results were achieved when 3.0 g/L Tween 80 was added to the fermentation broth on the 5th day of the fermentation, to give a maximum increase of 51.3 and 41.8% (p < 0.05) in the yield of mycelial biomass and BPS production, respectively. / The underlying mechanisms by which Tween 80 could increase the mycelial growth and EPS production in PTR were investigated by three novel approaches including changes in the nutrient uptake by mycelium, the morphology of mycelial pellets, and the fatty acid composition in the mycelial cell membrane. Firstly, the addition of Tween 80 significantly increased the glucose consumption rate by the mycelium, implying that the efficiency of nutrient uptake from the fermentation broth was enhanced. Secondly the addition of Tween 80 could extend the growth period of the mycelium possibly by maintaining the intact structure of the mycelial pellets and preventing its disintegration caused by shear stress in the fermentation system. Thirdly, the addition of Tween 80 could increase the incorporation of oleic acid which was a constituent of Tween 80 itself into the mycelial cell membrane of PTR, altering its fatty acid composition and increase the cell membrane permeability. The first two results explained the enhancement in the mycelial growth and EPS production while the last one was related to the extracellular transport of EPS to the fermentation broth. / This study aimed at comparing the effectiveness in the use of stimulatory agents with different chemical structures for enhancing the production of mycelial biomass and exopolysaccharide (BPS) by submerged fermentation of an edible mushroom Pleurotus tuber-regium (PTR). The chemical characteristics and antitumor activity of the BPS produced with and without the addition of the most effective stimulatory agent (Tween 80 which is a permitted food additive) were also compared. The underlying mechanisms by which Tween 80 could exert its effect on the mushroom mycelium were investigated by using chemical methods and microscopic techniques as well as proteomic analysis. / Zhang, Bobo. / Adviser: Chi Keung Peter Cheung. / Source: Dissertation Abstracts International, Volume: 73-08, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 132-156). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_345148 |
| Date | January 2011 |
| Contributors | Zhang, Bobo., Chinese University of Hong Kong Graduate School. Division of Life Sciences. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xv, 157 leaves : ill. (some col.)) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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