Mediterranean Institute of Oceanology (MIO), Aix-Marseille Université, 163 avenue de Luminy, 13288, Marseille Cedex 9, France.
Mediterranean Institute of Marine and Terrestrial Biodiversity and Ecology (IMBE), Aix-Marseille Université, 27 Boulevard Jean Moulin, 13385, Marseille Cedex 5, France.
Sci Rep. 2021 Apr 20;11(1):8538. doi: 10.1038/s41598-021-87328-2.
Pyomelanin is a polymer of homogentisic acid synthesized by microorganisms. This work aimed to develop a production process and evaluate the quality of the pigment. Three procedures have been elaborated and optimized, (1) an HGA-Mn chemical autoxidation (Pyo yield 0.317 g/g substrate), (2) an induced bacterial culture of Halomonas titanicae through the 4-hydroxyphenylacetic acid-1-hydroxylase route (Pyo, 0.55 g/L), and (3) a process using a recombinant laccase extract with the highest level produced (Pyo, 1.25 g/g substrate) and all the criteria for a large-scale prototype. The chemical structures had been investigated by C solid-state NMR (CP-MAS) and FTIR. C-C bindings predominated in the three polymers, C-O-C (ether) linkages being absent, proposing mainly C-C (α-bindings) and C-C (β-bindings) configurations. This work highlighted a biological decarboxylation by the laccase or bacterial oxidase(s), leading to the partly formation of gentisyl alcohol and gentisaldehyde that are integral parts of the polymer. By comparison, Pyo exhibited an M of 5,400 Da, was hyperthermostable, non-cytotoxic even after irradiation, scavenged ROS induced by keratinocytes, and had a highly DPPH-antioxidant and Fe-reducing activity. As a representative pigment of living cells and an available standard, Pyo might also be useful for applications in extreme conditions and skin protection.
焦黑素是一种由微生物合成的均苯三酸聚合物。本工作旨在开发一种生产工艺并评估该色素的质量。已详细阐述和优化了三个程序，（1）HGA-Mn 化学自氧化（产率为 0.317 g/g 底物），（2）通过 4-羟基苯乙酸-1-羟化酶途径诱导 Halomonas titanicae 细菌培养（产率为 0.55 g/L），和（3）使用最高产量的重组漆酶提取物的工艺（产率为 1.25 g/g 底物），并且符合大规模原型的所有标准。通过 C 固态 NMR（CP-MAS）和 FTIR 研究了化学结构。在这三种聚合物中，C-C 键占主导地位，不存在 C-O-C（醚）键，主要提出了 C-C（α-键合）和 C-C（β-键合）的构型。这项工作突出了漆酶或细菌氧化酶的生物脱羧作用，导致部分形成均苯三酚醇和均苯三甲醛，它们是聚合物的组成部分。相比之下，Pyo 的分子量为 5400 Da，具有超耐热性，即使在照射后也没有细胞毒性，可清除角质形成细胞诱导的 ROS，并具有高度的 DPPH 抗氧化和 Fe 还原活性。作为活细胞的代表性色素和可用标准，Pyo 也可能适用于极端条件和皮肤保护的应用。
