Stimulatory effect of ethanol on libertellenone H biosynthesis by Arctic fungus Eutypella sp. D-1

Genome Mining Leads to Diverse Sesquiterpenes with Anti-inflammatory Activity from an Arctic-Derived Fungus

With the advancement of bioinformatics, the integration of genome mining with efficient separation technology enables the discovery of a greater number of novel bioactive compounds. The deletion of the key gene responsible for triterpene cyclase biosynthesis in the polar strain Eutypella sp. D-1 instigated metabolic shunting, resulting in the activation of dormant genes and the subsequent production of detectable, new compounds. Fifteen sesquiterpenes were isolated from the mutant strain, with eight being new compounds. The structural elucidation of these compounds was obtained through a combination of HRESIMS, NMR spectroscopy, and ECD calculations, revealing six distinct skeleton types. Compound 7 possessed a unique skeleton of 5/10 macrocyclic ether structure. Based on the gene functions and newly acquired secondary metabolites, the metabolic shunting pathway in the mutant strain was inferred. Compounds 6, 8, 11, 14, and 15 exhibited anti-inflammatory effects without cytotoxicity through the release of nitric oxide from lipopolysaccharide-stimulated RAW264.7 cells. Notably, acorane-type sesquiterpene 8 inhibited nitric oxide production and modulated the MAPK and NLRP3/caspase-1 signaling pathways. Compound 8 also alleviated the CuSO4-induced systemic neurological inflammation symptoms in a transgenic fluorescent zebrafish model.

Pimarane-Type Diterpenes with Anti-Inflammatory Activity from Arctic-Derived Fungus Eutypella sp. D-1

The Arctic-derived fungus Eutypella sp. D-1 can produce numerous secondary metabolites, and some compounds exhibit excellent biological activity. Seven pimarane-type diterpenes, including three new compounds eutypellenone F (1), libertellenone Y (2), and libertellenone Z (3), and four known compounds (4-7), were isolated from fermentation broth of Eutypella sp. D-1 by the OSMAC strategy of adding ethanol as a promoter in the culture medium. Compound 2 has a rare tetrahydrofuran-fused pimarane diterpene skeleton. The anti-inflammatory activity of all compounds was evaluated. Compounds 3-6 showed a significant inhibitory effect on cell NO release at 10 μmol/L by in vitro experiments, of which 3-5 had inhibitory rates over 60% on nitric oxide (NO) release. Subsequently, the anti-inflammatory activity of 3-5 was evaluated based on a zebrafish model, and the results showed that 3 had a significant inhibitory effect on inflammatory cells migration at 40 μmol/L, while 4 and 5 had a significant inhibitory effect at 20 μmol/L. Moreover, compounds 3-5 have the same conjugated double bond structure, which may be an important group for these compounds to exert anti-inflammatory activity.

Optimization of Protoplast Preparation and Establishment of Genetic Transformation System of an Arctic-Derived Fungus Eutypella sp

Arctic-derived fungus Eutypella sp. D-1 has attracted wide attention due to its huge ability to synthesize secondary metabolites. However, current studies only focus on stimulating its production of new secondary metabolites by OSMAC strategies, and the relationship between secondary metabolites and biosynthetic gene clusters (BGCs) has not been explored. In this study, the preparation and regeneration conditions of Eutypella sp. D-1 protoplasts were explored to lay a foundation for the study of genetic transformation of this fungus. Orthogonal experiment showed that the optimal preparation conditions were 0.75 M NaCl, 20 g/L of lysing enzyme, and 20 g/L of driselase, 28°C for 6 h. The maximum yield of Eutypella sp. D-1 protoplasts could reach 6.15 × 10⁶ cells·ml⁻¹, and the concentration of osmotic stabilizer NaCl was the most important factor for Eutypella sp. D-1 protoplasts. The results of FDA staining showed that the prepared protoplasts had good activity. Besides, the best protoplasts regeneration medium was YEPS, whose maximum regeneration rate is 36%. The mediums with nitrogen sources, such as SR and RM, also had good effects on the Eutypella sp. D-1 protoplast regeneration, indicating that nitrogen sources played an important role on the Eutypella sp. D-1 protoplast regeneration. Subsequent transformation experiments showed that hygromycin resistance genes (hrg) could be successfully transferred into the genome of Eutypella sp. D-1, indicating that the prepared protoplasts could meet the needs of subsequent gene manipulation and research. This study lays a foundation for the genetic transformation of Eutypella sp. D-1.

Combinatorial strategies for production improvement of red pigments from Antarctic fungus Geomyces sp

Natural red pigments have been widely used as food and cosmetics additives. However, due to toxic byproducts or allergen issues, it is still necessary to look for some other red pigment products. This study proposed combinatorial strategies to improve production of a new kind of red pigments from the fungus Geomyces WNF-15A, isolated from Antarctica. A high-production medium was developed by statistical experimental design, which was further simplified for industrial use by single-factor experiments. Strain breeding by atmospheric room temperature plasma mutagenesis generated a mutant, Geomyces sp. WNF-15A-M210, which increased production of red pigments by 24.4% and shortened culture phase by 33.3% comparing with the wild-type. The production of red pigments by this mutant favored a weak alkaline condition but required only mild dissolved oxygen tension. Control of initial pH 8.5 (process pH around 7.5) increased red pigments production by 19% comparing with natural condition. Precursor and inhibitor addition experiments indicated that the red pigments were synthesized by polyketide pathway, and feeding 6 mmol/L precursor of sodium acetate by three aliquots at days 3 to 5 improved biosynthesis of red pigments by 27%. Finally, the developed culture process was verified in a 5-L stirred tank bioreactor. The red pigments production of the pH regulation group reached 1.11-fold of the control and 1.95-fold of the precursor regulation group, respectively. This study provides high-production strain, optimized medium, and bioprocess for the possible industrial production of Antarctic Geomyces red pigments in future. PRACTICAL APPLICATION: Antarctic Geomyces red pigments showed high color value, nontoxic characteristic, and good water solubility. It holds potential for industrial use and is under development for food additive in China currently. This study provides an optional manufacturing process for this new kind of red pigments.

Novel Natural Products from Extremophilic Fungi

Extremophilic fungi have been found to develop unique defences to survive extremes of pressure, temperature, salinity, desiccation, and pH, leading to the biosynthesis of novel natural products with diverse biological activities. The present review focuses on new extremophilic fungal natural products published from 2005 to 2017, highlighting the chemical structures and their biological potential.