Microbial production of a poly (γ-glutamic acid) derivative by Bacillus subtilis
Microbial production of a poly (γ-glutamic acid) derivative by Bacillus subtilis
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DOI：
10.1016/j.procbio.2004.12.009
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发表时间：
2005-07-01
影响因子：
4.4
通讯作者：
Shieh, CJ
中科院分区：
文献类型：
--
作者：
Shih, IL;Wu, PJ;Shieh, CJ
研究了枯草芽孢杆菌 Cl，一种能够产生甘油和 γ-PGA 生物结合物的细菌。 C1 是一种不依赖谷氨酸的细菌，在缺乏 L-谷氨酸的情况下产生 γ-PGA 衍生物。当细菌在培养基T中37℃、150rpm培养6天时，产生大量的生物结合物，21.4g/l。通过凝胶渗透色谱法测定，生物结合物的数均分子量 (M) 超过 1 x 107，氨基酸分析仅显示谷氨酸峰，H-1 NMR 谱显示 γ-PGA 和甘油的化学位移。在所用条件下生产的每种生物结合物中 D-谷氨酸含量均超过 97%，并且 D-谷氨酸含量与所研究的 Mn2+ 浓度无关。在生物缀合物生产过程中，检测到细胞内谷氨酸消旋酶活性，表明该酶参与 D-谷氨酸供应。生物结合物的分子量随培养基中盐浓度的变化而变化；培养4天后，分别含有0.05%和5% NaCl的培养物的分子量从7.94 x 10(6) Da下降到0.73 x 10(6) Da约10倍。 C1 产生的生物结合物的粘度明显高于 γ-PGA 本身。这种生物结合物是第一个由微生物直接产生的 γ-PGA 衍生物的例子；因此，它是一种独特的生物材料。 (c) 2005 Elsevier Ltd. 保留所有权利。
Bacillus subtilis Cl, a bacterium capable of producing a glycerol and gamma-PGA bioconjugate, was studied. C1 is a glutamate independent bacterium, which produces the gamma-PGA derivative in the absence of L-glutamate. A large amount of the bioconjugate, 21.4 g/l, was produced when the bacteria were cultured in medium T at 37 C, 150 rpm for 6 days. The number-average molecular weight (M) of the bioconjugate was over 1 x 107 as determined by gel permeation chromatography, amino acid analysis showed only glutamic acid peak and the H-1 NMR spectrum showed chemical shifts of both gamma-PGA and glycerol. The D-glutamate content was over 97% in every bioconjugate produced under the conditions used and the D-glutamate content was indifferent to the Mn2+ concentrations under study. During bioconjugate production, an intracellular glutamate racemase activity was detected, suggesting the enzyme is involved in the D-glutamate supply. The molecular weight of the bioconjugate varied with salt concentration in the medium; the molecular weight decreased by a factor of approximately 10 from 7.94 x 10(6) to 0.73 x 10(6) Da at 4-day cultivation time for cultures, which contained 0.05 and 5% NaCl, respectively. The viscosity of the bioconjugate produced by C1 is significantly higher than that of gamma-PGA itself. This bioconjugate is the first example of gamma-PGA derivative directly produced by microbes; thus, it is a unique biomaterial. (c) 2005 Elsevier Ltd. All rights reserved.