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首页> 外文期刊>Journal of Biotechnology >Carotenoid accumulation in bacteria with enhanced supply of isoprenoid precursors by upregulation of exogenous or endogenous pathways
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Carotenoid accumulation in bacteria with enhanced supply of isoprenoid precursors by upregulation of exogenous or endogenous pathways

机译：通过上调外源或内源性途径增加类异戊二烯前体的供应，细菌中的类胡萝卜素积累

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摘要

Carotenoids are isoprenoid pigments of industrial and nutritional interest. Although they are produced in non-carotenogenic Escherichia coli engineered with the appropriate biosynthetic genes, only a limited pool of their metabolic precursors is available in these bacteria. We have compared the production of carotenoids (lycopene) in strains in which the supply of precursors was enhanced either by upregulating the endogenous pathway via overexpression of deoxyxylulose 5-phosphate synthase (DXS) or by incorporating an exogenous MVA+ operon. In strains expressing DXS under the control of a leaky IPTG-inducible promoter, lycopene accumulation was increased up to 8-fold in the absence of inducer. Addition of IPTG, however, negatively affected lycopene production. Although induction of too high levels of the MVA+ operon enzymes also appeared to cause interference with cell metabolism, supplementation with mevalonate (to be metabolized into carotenoid precursors) resulted in a 10-fold increase in lycopene levels in cells with a near wild-type background. An additional 2-fold increase (up to 228mg/l) was obtained using an engineered BL21 strain. These results confirm that the MVA+ pathway is most convenient to upregulate the production of carotenoids (lycopene) production in E. coli but that factors other than precursor supply should be considered for high pigment accumulation levels.
机译：类胡萝卜素是具有工业和营养价值的类异戊二烯颜料。尽管它们是在用适当的生物合成基因改造的非致龋性大肠杆菌中产生的，但这些细菌中只有有限的代谢前体池可用。我们比较了菌株中类胡萝卜素（番茄红素）的生产，在这些菌株中，通过过表达脱氧木酮糖5-磷酸合酶（DXS）的内源途径或通过掺入外源性MVA +操纵子来增强前体的供应。在泄漏的IPTG诱导型启动子的控制下表达DXS的菌株中，在没有诱导剂的情况下，番茄红素的积累增加到8倍。然而，添加IPTG对番茄红素的生产产生负面影响。尽管诱导过高水平的MVA +操纵子酶也似乎会干扰细胞代谢，但是补充甲羟戊酸酯（会被代谢成类胡萝卜素前体）会使具有近乎野生型背景的细胞中番茄红素水平增加10倍。使用改造的BL21菌株获得了额外的2倍增加（最高228mg / l）。这些结果证实，MVA +途径最方便地上调大肠杆菌中类胡萝卜素（番茄红素）的生产，但是对于高色素积累水平，应考虑前体供应以外的因素。

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