Carotenoids are natural tetraterpene pigments widely utilized in the food, pharmaceutical and cosmetic industries. Currently, chemical synthesis of these compounds outperforms their production in Escherichia coli or yeast due to the limited efficiency of the latter. The use of natural microbial carotenoid producers, such as bacteria of the genus Paracoccus (Alphaproteobacteria), may help to optimize this process. In order to couple the ability to synthesize these pigments with the metabolic versatility of this genus, we explored the possibility of introducing carotenoid synthesis genes into strains capable of efficient growth on simple low-cost media. We constructed two carotenoid-producing strains of Paracoccus carrying a new plasmid, pCRT01, which contains the carotenoid synthesis gene locus crt from Paracoccus marcusii OS22. The plasmid was created in vivo via illegitimate recombination between crt-carrying vector pABW1 and a natural “paracoccal” plasmid pAMI2. Consequently, the obtained fusion replicon is stably maintained in the bacterial population without the need for antibiotic selection. The introduction of pCRT01 into fast-growing “colorless” strains of Paracoccus aminophilus and Paracoccus kondratievae converted them into efficient producers of a range of both carotenes and xanthophylls. The exact profile of the produced pigments was dependent on the strain genetic background. To reduce the cost of carotenoid production in this system, we tested the growth and pigment synthesis efficiency of the two strains on various simple media, including raw industrial effluent (coal-fired power plant flue gas desulfurization wastewater) supplemented with molasses, an industrial by-product rich in sucrose. We demonstrated a new approach for the construction of carotenoid-producing bacterial strains which relies on a single plasmid-mediated transfer of a pigment synthesis gene locus between Paracoccus strains. This strategy facilitates screening for producer strains in terms of synthesis efficiency, pigment profile and ability to grow on low-cost industrial waste-based media, which should increase the cost-effectiveness of microbial production of carotenoids.

中文翻译：

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质粒pCRT01的体内产生及其在生产类胡萝卜素副球菌中的应用。可在工业废物上有效生长的菌株。

类胡萝卜素是天然的四萜烯颜料，广泛用于食品，制药和化妆品行业。当前，由于大肠杆菌或酵母的效率有限，这些化合物的化学合成优于其在大肠杆菌或酵母中的生产。使用天然微生物类胡萝卜素生产商，如副球菌（Alphaproteobacteria）细菌，可能有助于优化这一过程。为了将合成这些色素的能力与该属的代谢多功能性结合起来，我们探索了将类胡萝卜素合成基因引入能够在简单的低成本培养基上有效生长的菌株中的可能性。我们构建了携带新质粒pCRT01的两种产副球菌类胡萝卜素的菌株，该质粒包含来自Marcusii marcusii OS22的类胡萝卜素合成基因基因座crt。通过携带crt的载体pABW1和天然“副球菌”质粒pAMI2之间的非法重组，在体内创建了质粒。因此，获得的融合复制子稳定地保持在细菌群体中，而无需选择抗生素。将pCRT01引入快速增长的“无色”嗜热副球菌和kondratievae副球菌菌株后，将其转化为一系列胡萝卜素和叶黄素的有效生产者。产生的颜料的确切轮廓取决于菌株的遗传背景。为了降低该系统中类胡萝卜素的生产成本，我们测试了两种菌株在各种简单培养基上的生长和色素合成效率，包括添加了糖蜜的工业原料废水（燃煤电厂烟气脱硫废水），一种富含蔗糖的工业副产品。我们展示了一种构建类胡萝卜素细菌菌株的新方法，该菌株依赖于单质粒介导的副球菌菌株之间色素合成基因基因座的转移。该策略有助于从合成效率，色素分布和在低成本的基于工业废物的培养基上生长的能力方面筛选生产菌株，这将增加微生物生产类胡萝卜素的成本效益。