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[求助]
求助一篇英文文献，有效期至08年11月23日
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题目为γ-Poly(glutamic acid)Formation by Bacillus licheniformis hysiological and Biochemical Studies |
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abstract
★ ★ ★
tiantianbaobao(金币+3,VIP+0):谢谢，估计这篇文献是找不到了。
tiantianbaobao(金币+3,VIP+0):谢谢，估计这篇文献是找不到了。
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查不到全文，给一些信息吧，方便别人查 γ-Poly(glutamic acid) formation by Bacillus licheniformis 9945a: physiological and biochemical studies Gregory A. Birrer*, a, Anne-Marie Cromwicka and Richard A. Gross, a aUniversity of Massachusetts Lowell, Department of Chemistry, One University Avenue, Lowell, MA 01854, USA Received 8 March 1994; revised 5 August 1994. Available online 27 January 2003. Abstract Cryogenically frozen vegetative cells of Bacillus licheniformis 9945a derived from young mucoid colonies were used to inoculate γ-poly(glutamate) (γ-PGA) production media containing l-glutamate, citrate and glycerol as carbon sources. A gel permeation chromatography (GPC) method was developed to determine γ-PGA volumetric yield and molecular weight directly using culture filtrates. For GPC volumetric yield measurements, a calibration curve was generated using purified γ-PGA to relate the γ-PGA GPC peak area and polymer weight. Purified γ-PGA was characterized by elemental analysis, 1H- and 13C-NMR spectroscopy. Cultures of B. licheniformis using all three carbon sources showed the following characteristics: cell growth mainly during the first 24 h; largest γ-PGA volumetric productivity (0.12 gl−1 h−1) between 48 and 96 h; 11 gl−1 γ-PGA volumetric yield by 96 h; reduction (utilization) of glycerol, glutamate and citrate during a 96 h cultivation time from 80 to 45 gl−1, 18 to 10 gl−1 and 12 to 1 gl−1, respectively; a decrease in pH from 7.4 to 5.5 by 42 h cultivation; acetic acid secretion into the medium at a maximum level of 4.5 gl−1 and detection of the metabolite 2,3-butanediol (as acetoin) as a fermentation by-product at 42 h and through a 96 h cultivation period. The presence of 2,3-butanediol indicated that the level of oxygen in the medium no longer supported a fully aerobic mode of metabolism. When the medium formulation was altered by removal of either citrate, l-glutamate or glycerol in shake flask experiments where pH was not controlled, 2.3, 9.0 and 4.0 gl−1, respectively, of γ-PGA were formed. Variation of the medium ionic strength by the addition of up to 4% (w/v) NaCl led to the formation of γ-PGA of relatively higher molecular weight but lower volumetric yield. Studies carried out on 5-day-old B. licheniformis cultures suggested that γ-PGA depolymerase is intracellularly located or cell-bound. Culture filtrates showed no significant γ-PGA depolymerase activity. Keywords: Bacillus licheniformis 9945a; γ-poly(glutamate); gel permeation chromatography |
4楼2008-11-13 11:21:15
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