Synthetic dyes are widely used in the industry; they are chemically stable, difficult to neutralize, and therefore they are a threat to the environment when released into wastewaters. The dyes have a significant impact on plant performance by impairing photosynthesis, inhibiting growth, and entering the food chain and may finally result in the toxicity, mutagenicity and carcinogenicity of food products. Implementation of the dark piment melanin for the adsorption of the synthetic dyes is a new ecologically friendly approach for bioremediation. The aim of the present work was to study the physico-chemical characteristics of melanins from the lichens Lobaria pulmonaria and Lobaria retigera, analyze their adsorption/desorption capacities towards synthetic dyes, and assess the capacity of melanins to mitigate toxicity of the dyes for a common soil bacterium Bacillus subtilis. Unique chelating properties of melanins determine the perspectives of the use of these high molecular weight polymers for detoxification of xenobiotics.

Lichens are unique extremophilic organisms due to their phenomenal resistance to adverse environmental factors, including ultraviolet (UV) irradiation. Melanization plays a special role in the protection of lichens from UV-B stress. In the present study, we analyzed the binding of melanins with the components of cell walls of the mycobiont of the upper cortex in the melanized lichen thalli Lobaria pulmonaria. Using scanning electron and atomic force microscopy, the morphological and nanomechanical characteristics of the melanized layer of mycobiont cells were visualized. Melanization of lichen thalli led to the smoothing of the surface relief and thickening of mycobiont cell walls, as well as the reduction in adhesion properties of the lichen thallus. Treatment of thalli with hydrolytic enzymes, especially chitinase and lichenase, enhanced the yield of melanin from melanized thalli and promoted the release of carbohydrates, while treatment with pectinase increased the release of carbohydrates and phenols. Our results suggest that melanin can firmly bind with hyphal cell wall carbohydrates, particularly chitin and 1,4-β-glucans, strengthening the melanized upper cortex of lichen thalli, and thereby it can contribute to lichen survival under UV stress.

Lichens are symbiotic organisms that effectively survive in harsh environments, including arid regions. Maintaining viability with an almost complete loss of water and the rapid restoration of metabolism during rehydration distinguishes lichens from most eukaryotic organisms. The lichen Xanthoria parietina is known to have high stress tolerance, possessing diverse defense mechanisms, including the presence of the bright-orange pigment parietin. While several studies have demonstrated the photoprotective and antioxidant properties of this anthraquinone, the role of parietin in the tolerance of lichens to desiccation is not clear yet. Thalli, which are exposed to solar radiation and become bright orange, may require enhanced desiccation tolerance. Here, we showed differences in the anatomy of naturally pale and bright-orange thalli of X. parietina and visualized parietin crystals on the surface of the upper cortex. Parietin was extracted from bright-orange thalli by acetone rinsing and quantified using HPLC. Although acetone rinsing did not affect PSII activity, thalli without parietin had higher levels of lipid peroxidation and a lower membrane stability index in response to desiccation. Furthermore, highly pigmented thalli possess thicker cell walls and, according to thermogravimetric analysis, higher water-holding capacities than pale thalli. Thus, parietin may play a role in desiccation tolerance by stabilizing mycobiont membranes, providing an antioxidative defense, and changing the morphology of the upper cortex of X. parietina.

Выделение штамма Inonotus obliquus и интенсификация роста культуры при твердофазном культивировании

Extremophile organisms can survive under extreme conditions through tolerance mechanisms. Such organisms include lichens, which are symbiotic associations of fungi and algae and/or cyanobacteria. Among other factors, the high stress tolerance of lichens can be attributed to their ability to synthesize a wide range of metabolites, including chemically diverse lipid compounds. Despite their obvious relevance, the biochemical mechanisms of stress tolerance in lichens that are mediated by changes in the lipid profile remain understudied. Peltigerous lichens constitute a separate division of lichens characterized by high growth rates and metabolic activity indices. Taking into account the temperate climate in which these lichens grow, it can be assumed that they may be highly sensitive to temperature fluctuations. These factors led to the choice of Peltigera canina, epigeic lichen, as the subject matter of this study. The present work examined stress-induced changes in the redox status of P. canina, as well as changes in its lipid composition at an elevated temperature (40 °С). The exposure of hydrated lichen thalli to an unfavorable temperature led to an increase in the level of hydrogen peroxide, phenoloxidase activity, and lipid peroxidation, which constitutes an important part of stress response in lichen. The stress-induced changes in the redox status of lichen thalli stimulated an increase in lipophilic antioxidant agents: a dramatic increase in the level of α-tocopherol and an increase in carotenoids, specifically β-carotene. Thus, the accumulation of lipophilic antioxidants constitutes an important part of the lipid-mediated stress response of P. canina to temperature elevation.

Many members of the Asparagaceae family are used in traditional medicine in different countries and characterized by a high content of biologically active metabolites. In this work, the qualitative composition and quantitative content of the components of methanol extracts from leaves and underground organs of Sansevieria cylindrica Bojer ex Hook, Sansevieria trifasciata Prain, Polianthes tuberosa L., leaves of Yucca filamentosa L. and Furcraea gigantea var. watsoniana (Hort. Sander) Drumm. were determined. Extraction of plant leaves and underground organs using 80% methanol resulted in 5.2–16.7% and 16–25.1% of the total extractive substances consequently. The presence of steroidal saponins in the extracts was shown by thin layer chromatography. Spirostanol saponins were predominate in the extracts from leaves of Y. filamentosa, F. gigantea and underground organs of S. cylindrica, S. trifasciata, P. tuberosa, furastanol saponins – in the extracts from leaves of S. cylindrica and S. trifasciata. The content of terpenoid and phenolic compounds in the extracts established using spectrophotometry significantly differs depending on the plant species and their anatomical part. All the extracts tested exhibited inhibition of the 2,2-diphenyl-1-picrylhydrazyl free radical in dose-dependent manner. The highest antiradical activity demonstrated the extract from the leaves of Y. filamentosa (IC50 = 25.95 μg/ml) containing the largest amount of phenolic compounds, including flavonoids – 51.3 and 15.5% of the total extractive substances.