Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096, Warsaw, Poland.
Department of Environmental Microbiology and Biotechnology, Institute of Microbiology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096, Warsaw, Poland.
Microb Cell Fact. 2020 Jul 13;19(1):141. doi: 10.1186/s12934-020-01396-z.
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.
类胡萝卜素是一种广泛应用于食品、制药和化妆品行业的天然四萜类色素。由于后者的效率有限，目前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者，如 Paracoccus 属（α变形菌）的细菌，可能有助于优化这个过程。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低成本培养基上高效生长的菌株中的可能性。
我们构建了两个能够生产类胡萝卜素的 Paracoccus 菌株，它们携带一个新的质粒 pCRT01，该质粒含有来自 Paracoccus marcusii OS22 的类胡萝卜素合成基因座 crt。该质粒是通过 crt 携带载体 pABW1 与天然“副球菌”质粒 pAMI2 之间的非法重组在体内创建的。因此，获得的融合复制子无需抗生素选择即可在细菌群体中稳定维持。将 pCRT01 引入快速生长的“无色”Paracoccus aminophilus 和 Paracoccus kondratievae 菌株，将它们转化为一系列类胡萝卜素和叶黄素的高效生产者。所产生的色素的确切特征取决于菌株的遗传背景。为了降低该系统中类胡萝卜素生产的成本，我们在各种简单培养基上测试了两种菌株的生长和色素合成效率，包括补充糖蜜的原始工业废水（燃煤电厂烟气脱硫废水），糖蜜是一种富含蔗糖的工业副产物。
我们展示了一种新的方法，用于构建依赖于质粒介导的在 Paracoccus 菌株之间转移色素合成基因座的类胡萝卜素生产菌株。该策略有利于根据合成效率、色素特征和在低成本工业废物基培养基上生长的能力筛选生产菌株，这应该提高微生物类胡萝卜素生产的成本效益。
