Department of Microbiology, University of Innsbruck, 6020, Innsbruck, Austria.
Department of Biotechnology and Food Engineering, MCI-The Entrepreneurial School, 6020, Innsbruck, Austria.
Photochem Photobiol Sci. 2023 Dec;22(12):2861-2875. doi: 10.1007/s43630-023-00493-3. Epub 2023 Oct 28.
The demand for natural pigments in general, and for fungi-derived pigments in particular, is constantly rising. Wood-decomposing fungi represent a promising source for natural pigments and they are usually easy to cultivate in pure culture. One of them, i.e., Pycnoporus cinnabarinus, offers a highly interesting spectrum of bioactivity, partly due to the formation of the orange-red pigment cinnabarin. However, apart from a few studies addressing its diverse potential biotechnological applications, there is still a large gap of knowledge concerning the influence of light on the formation of cinnabarin. The aim of this work was to investigate the effect of different irradiations on the cinnabarin content, the growth, and the morphology of three different P. cinnabarinus strains. We used highly standardized irradiation conditions and cultivation techniques in combination with newly developed methods for the extraction and direct quantification of cinnabarin.
Red, green, blue, and UV-A irradiation (mean irradiance E = 1.5 ± 0.18 W m) had considerable effects on the growth and colony appearance of all three P. cinnabarinus strains tested. The cinnabarin content determined was, thus, dependent on the irradiation wavelength applied, allowing strain-specific thresholds to be defined. Irradiation with wavelengths below this strain-specific threshold corresponded to a lower cinnabarin content, at least at the intensity applied. The orange-red pigment appeared by light microscopy as incrusted extracellular plaques present on the hyphal walls. Highly efficient vegetative propagation occurred by arthroconidia, and we observed the tendency that this asexual reproduction was (i) most frequent in the dark but (ii) never occurred under UV-A exposure.
This study highlights a differential photo-dependence of growth, morphology, and cinnabarin formation in P. cinnabarinus. This confirms that it is advisable to consider the wavelength of the light used in future biotechnological productions of natural pigments.
对天然色素的需求不断增长，特别是对真菌来源的色素的需求不断增长。木质分解真菌是天然色素的一个很有前途的来源，它们通常很容易在纯培养中培养。其中一种，即红栓菌，提供了一个非常有趣的生物活性谱，部分原因是形成橙红色色素红紫素。然而，除了少数研究探讨了其多种潜在的生物技术应用外，对于光照对红紫素形成的影响，我们仍然知之甚少。本工作的目的是研究不同辐射对三种不同红栓菌菌株的红紫素含量、生长和形态的影响。我们使用高度标准化的辐射条件和培养技术，结合新开发的红紫素提取和直接定量方法。
红、绿、蓝和 UV-A 辐射（平均辐照度 E=1.5±0.18 W m）对所有三种测试的红栓菌菌株的生长和菌落外观都有很大的影响。因此，所测定的红紫素含量取决于所应用的辐射波长，允许定义菌株特异性阈值。在低于该菌株特异性阈值的波长下进行辐照，至少在应用的强度下，对应于较低的红紫素含量。橙红色色素在光学显微镜下表现为附着在菌丝壁上的细胞外斑块。高效的营养繁殖通过节孢子发生，我们观察到这种无性繁殖（i）在黑暗中最常见，但（ii）在 UV-A 暴露下从未发生。
本研究强调了红栓菌的生长、形态和红紫素形成的差异光依赖性。这证实了在未来的天然色素生物技术生产中，考虑所使用光的波长是明智的。
