Medium optimization for the high yield production of single (+)-terrein by Aspergillus terreus strain PF26 derived from marine sponge Phakellia fusca

Terrein: isolation, chemical synthesis, bioactivity and future prospects of a potential therapeutic fungal metabolite

The increasing risk of drug-resistant infections and unexpected pandemics like Covid-19 has prompted researchers to explore the area of drug repurposing. Natural products, being a result of the evolutionary optimisation processes can be potential starting points for such drug discovery programs. One such unexplored chemical is terrein, a secondary fungal metabolite. Although discovered in 1935 from Aspergillus terreus, the therapeutic potential of terrein has largely remained undeciphered. Research has primarily been focused on its biosynthetic pathways and its mycotoxic effects. However, in the last two decades, its biological properties including anticancer, anti-inflammatory anti-melanogenic, and bacteriocidal activities have been reported. These reports are preliminary in nature and do not adequately establish its overall therapeutic application. From its structural and therapeutic properties, it can be conjectured that terrein may act as a novel multimodal therapeutic. This comprehensive study reviews the synthesis, production and application aspects of terrein to understand its importance.

Unveiling the dermatological potential of marine fungal species components: Antioxidant and inhibitory capacities over tyrosinase

Marine fungi are a rich source of biologically active molecules, but a poorly explored bioresource for cosmeceutical products. This study evaluates the phytochemistry, antioxidant, and antityrosinase effects of the organic extracts of marine fungi isolated from various marine environments in India. Out of 35 screened fungal strains, methanol extracts of strains P2, Talaromyces stipitatus, and D4, Aspergillus terreus exhibited antityrosinase activity of 45% and 43%, respectively, at the lowest concentration of 0.5 mg/mL. The highest free radicals scavenging activity of 94% and 97% was observed at 500 mg/mL, respectively, of the same fungal extracts. The total phenolic content ranged from 8.20 to 20.30 mg/g of the dry weight of extract, expressed as gallic acid equivalent. GC-MS analysis of T. stipitatus and A. terreus extract identified seven and 10 major compounds, respectively. Some of the major compounds included azetidine, (3E)-3-[(3,5-dimethoxybenzoyl)hydrazono]-N-isobutyl butanamide, aziridine, and 3-methylcyclopentanone, 1,1-dimethylcyclohexane, cyclopentane carboxylic acid, N-allyl-4,5,6,7-tetrahydro-2-benzothiophene-1-carboxamide, cyclo(l-Pro-l-Val), and 3-phenylpropionitrile. In conclusion, this study showed abundant fungal resources in Indian marine environments. A correlation between total phenolic contents of the extracts confirmed that phenolic compounds play an important role in antioxidant as well as antityrosinase activity of the marine fungal extracts and can be viewed as new potential antityrosinase and antioxidant resources.

Large-Scale Production of Bioactive Terrein by Aspergillus terreus Strain S020 Isolated from the Saudi Coast of the Red Sea

The diversity of symbiotic fungi derived from two marine sponges and sediment collected off Obhur, Jeddah (Saudi Arabia), was investigated in the current study. A total of 23 isolates were purified using a culture-dependent approach. Using the morphological properties combined with internal transcribed spacer-rDNA (ITS-rDNA) sequences, 23 fungal strains (in the majority Penicillium and Aspergillus) were identified from these samples. The biological screening (cytotoxic and antimicrobial activities) of small-scale cultures of these fungi yielded several target fungal strains which produced bioactive secondary metabolites. Amongst these isolates, the crude extract of Aspergillus terreus strain S020, which was cultured in fermentation static broth, 21 L, for 40 days at room temperature on potato dextrose broth, displayed strong antimicrobial activities against Pseudomonas aeruginosa and Staphylococcus aureus and significant antiproliferative effects on human carcinoma cells. Chromatographic separation of the crude extract by silica gel column chromatography indicated that the S020 isolate could produce a series of chemical compounds. Among these, pure crystalline terrein was separated with a high yield of 537.26 ± 23.42 g/kg extract, which represents the highest fermentation production of terrein to date. Its chemical structure was elucidated on the basis of high-resolution electrospray ionization mass spectrometry (HRESIMS) or high-resolution mass spectrometry (HRMS), 1D, and 2D NMR spectroscopic analyses and by comparison with reported data. The compound showed strong cytotoxic activity against colorectal carcinoma cells (HCT-116) and hepatocellular carcinoma cells (HepG2), with IC₅₀ values of 12.13 and 22.53 µM, respectively. Our study highlights the potential of A. terreus strain S020 for the industrial production of bioactive terrein on a large scale and the importance of future investigations of these strains to identify the bioactive leads in these fungal extracts.

Protein improvement of banana peel through sequential solid state fermentation using mixed-culture of Phanerochaete chrysosporium and Candida utilis

Banana peel (BP) is a major waste produced by fruit processing industries. Pre-treatment of BP at different temperatures led to 40% reduction in saponin at 100 °C (from 9.5 to 5.7 mg/g). Sequential mixed culture of Phanerochaete chrysosporium (P. chrysosporium) and Candida utilis (C. utilis) gave highest protein enrichment (88.93 mg/g). There is 26% increase in protein synthesis (from 88.93 to 111.78 mg/g) after media screening. Inclusion of KH₂PO₄, FeSO₄·7H₂O, wheat flour and sucrose in the media contributed positively to protein synthesis, while elevated concentration of urea, peptone, K₂HPO₄, KCl, NH₄H₂PO_4, and MgSO₄.7H₂O are required to reach optimum protein synthesis. Total soluble sugar (TSS), total reducing sugar (TRS) and total carbohydrate (CHO) consumption varied with respect to protein synthesis in all experimental runs. Optimum protein synthesis required 6 days and inclusion of 5% sucrose, 0.6% NH₄H₂PO₄, 0.4% KCl, and 0.5% MgSO₄·7H₂O as concentration media constituents to reach 140.95 mg/g protein synthesis equivalent to 300% increase over the raw banana peel protein content (35.0 mg/g).

Polyketides in Aspergillus terreus: biosynthesis pathway discovery and application

The knowledge of biosynthesis gene clusters, production improving methods, and bioactivity mechanisms is very important for the development of filamentous fungi metabolites. Metabolic engineering and heterologous expression methods can be applied to improve desired metabolite production, when their biosynthesis pathways have been revealed. And, stable supplement is a necessary basis of bioactivity mechanism discovery and following clinical trial. Aspergillus terreus is an outstanding producer of many bioactive agents, and a large part of them are polyketides. In this review, we took polyketides from A. terreus as examples, focusing on 13 polyketide synthase (PKS) genes in A. terreus NIH 2624 genome. The biosynthesis pathways of nine PKS genes have been reported, and their downstream metabolites are lovastatin, terreic acid, terrein, geodin, terretonin, citreoviridin, and asperfuranone, respectively. Among them, lovastatin is a well-known hypolipidemic agent. Terreic acid, terrein, citreoviridin, and asperfuranone show good bioactivities, especially anticancer activities. On the other hand, geodin and terretonin are mycotoxins. So, biosynthesis gene cluster information is important for the production or elimination of them. We also predicted three possible gene clusters that contain four PKS genes by homologous gene alignment with other Aspergillus strains. We think that this is an effective way to mine secondary metabolic gene clusters.

From Discovery to Production: Biotechnology of Marine Fungi for the Production of New Antibiotics

Filamentous fungi are well known for their capability of producing antibiotic natural products. Recent studies have demonstrated the potential of antimicrobials with vast chemodiversity from marine fungi. Development of such natural products into lead compounds requires sustainable supply. Marine biotechnology can significantly contribute to the production of new antibiotics at various levels of the process chain including discovery, production, downstream processing, and lead development. However, the number of biotechnological processes described for large-scale production from marine fungi is far from the sum of the newly-discovered natural antibiotics. Methods and technologies applied in marine fungal biotechnology largely derive from analogous terrestrial processes and rarely reflect the specific demands of the marine fungi. The current developments in metabolic engineering and marine microbiology are not yet transferred into processes, but offer numerous options for improvement of production processes and establishment of new process chains. This review summarises the current state in biotechnological production of marine fungal antibiotics and points out the enormous potential of biotechnology in all stages of the discovery-to-development pipeline. At the same time, the literature survey reveals that more biotechnology transfer and method developments are needed for a sustainable and innovative production of marine fungal antibiotics.

Modification of artificial sea water for the mass production of (+)-terrein by Aspergillus terreus strain PF26 derived from marine sponge Phakellia fusca

(+)-Terrein shows multiple bioactivities, however, its mass production is a big challenge. Aspergillus terreus strain PF26 derived from South China Sea sponge Phakellia fusca has been cultured to produce (+)-terrein successfully, but artificial sea water (ASW) of high salinity used in the fermentation medium may cause the corrosion risk of metal bioreactor, which limits the fermentation on a large scale. In this study, we modified the components of ASW by removing NaCl and CaCl2 from the original formula, which reduced about 80% salinity of ASW. As a result, 7·56 g l(-1) (+)-terrein production was achieved in shake flask, which was 78·72% higher than using the original ASW, and the cultivation time was decreased from 24 to 15 days. Then, the modified ASW was used for the fermentation of A. terreus strain PF26 in a 500 l stirred bioreactor, consequently 2·5 g l(-1) of (+)-terrein production was achieved.

SIGNIFICANCE AND IMPACT OF THE STUDY

The fermentation of marine micro-organisms always needs to use sea water or artificial sea water (ASW), which limits the fermentation on a large scale, as the high-salinity medium may cause the corrosion risk of bioreactor. In this study, the ASW formula is simplified to reduce the sea water salinity and improve the yield of (+)-terrein, finally, the modified ASW was successfully used for the mass production of (+)-terrein by A. terreus strain PF26 in a 500 l bioreactor.

(+)‑Terrein inhibits human hepatoma Bel‑7402 proliferation through cell cycle arrest

Hepatoma is a common malignant tumor. Thus, the development of a high‑efficacy therapeutic drug for hepatoma is required. In this study, (+)‑terrein isolated from the marine sponge‑derived Aspergillus terreus PF‑26 against cell growth, apoptosis and cell cycle were assessed by MTT and flow cytometry. mRNA array containing 73 cell cycle‑related genes and three cell morphology‑related genes was generated and its performance evaluated. The cell cycle pathway map was created using the pathview package. The results showed that (+)‑terrein inhibited the growth of Bel‑7402 cells with alterations in cell morphology and a reduced transcript expression of cell morphology genes (fibronectin, N‑cadherin, and vimentin). In addition, flow cytometric analysis revealed that (+)‑terrein arrested the Bel‑7402 cell cycle without inducing apoptosis. Based on multiple mRNA analysis, the downregulated expression of the CCND2, CCNE2, CDKN1C, CDKN2B, ANAPC, PKMYT1, CHEK2 and PCNA genes was observed in 10 µM (+)‑terrein‑treated Bel‑7402 cells (>2‑fold and P≤0.05), compared with the controls. Thus, the antiprolife-rative mechanism of (+)‑terrein against Bel‑7402 cells may be due to the cell cycle arrest by blocking cell cycle gene expression and changing cell morphology.

The marine-derived fungal metabolite, terrein, inhibits cell proliferation and induces cell cycle arrest in human ovarian cancer cells

The difficulties faced in the effective treatment of ovarian cancer are multifactorial, but are mainly associated with relapse and drug resistance. Cancer stem-like cells have been reported to be an important contributor to these hindering factors. In this study, we aimed to investigate the anticancer activities of a bioactive fungal metabolite, namely terrein, against the human epithelial ovarian cancer cell line, SKOV3, primary human ovarian cancer cells and ovarian cancer stem-like cells. Terrein was separated and purified from the fermentation metabolites of the marine sponge-derived fungus, Aspergillus terreus strain PF26. Its anticancer activities against ovarian cancer cells were investigated by cell proliferation assay, cell migration assay, cell apoptosis and cell cycle assays. The ovarian cancer stem-like cells were enriched and cultured in a serum-free in vitro suspension system. Terrein inhibited the proliferation of the ovarian cancer cells by inducing G2/M phase cell cycle arrest. The underlying mechanisms involved the suppression of the expression of LIN28, an important marker gene of stemness in ovarian cancer stem cells. Of note, our study also demonstrated the ability of terrein to inhibit the proliferation of ovarian cancer stem-like cells, in which the expression of LIN28 was also downregulated. Our findings reveal that terrein (produced by fermention) may prove to be a promising drug candidate for the treatment of ovarian cancer by inhibiting the proliferation of cancer stem-like cells.

Nutrition and bioprocess development for efficient biosynthesis of an antitumor compound from marine-derived fungus

An integrated nutrition and bioprocess strategy was developed for improving the biosynthesis of an antitumor compound, 1403C, by a marine-derived fungus, Halorosellinia sp. (no. 1403). First, statistical design strategies were synthetically applied to optimize the nutritional composition. The resulting 1403C production reached 2.07 g/l, which was 143.5 % higher than the original production. However, it only produced 0.44 g/l of 1403C in 5-l bioreactor fermentation. Thus, the operating parameters including culture pH, dissolved oxygen, agitation speed, impeller type and inoculum level were considered to improve the fermentation process, and an effective control strategy for 1403C production by Halorosellinia sp. submerged in a 5-l bioreactor was established. When inoculating 0.22 g/l dry biomass, controlling dissolved oxygen not lower than 30 % during the growth phase but ranging between 30 and 40 % during the stationary phase, using a double-layer six-flat-blade Rushton disc turbine agitated at 400 rpm, keeping short-term low pH and rapid-rising pH with glucose starvation, the highest 1403C production was finally obtained at 1.32 g/l, which was promoted by 200 % compared to before optimization. Fermentation scale-up was finally performed in a 500-l bioreactor, and 1403C production of 1.09 g/l was obtained.

Enhanced production of a novel cytotoxic chromone oxalicumone A by marine-derived mutant Penicillium oxalicum SCSIO 24-2

Many marine natural products hold great potential for the development of new and much needed drugs. However, the production of active metabolites by marine-derived microorganisms is usually very low, and large-scale culture has to be involved to meet the need of chemical structural modification and deep pharmacy study. In order to enhance the production of a novel cytotoxic sulfur-containing chromone oxalicumone A (OA), germinating spores of a marine-derived wild strain Penicillium oxalicum SCSGAF 0023 were mutated by microwave and ultraviolet light irradiation, which led to the obtainment of a mutant P. oxalicum SCSIO 24-2 that could produce fivefold increase in OA production (3.42 ± 0.21 mg/l) as compared to the wild strain. This is the first report that germinating spores are applied in marine-derived Penicillium sp. mutating to enhance the production of OA. Further, Plackett-Burman design and central composite design were adopted to optimize the basic medium components for increasing OA production by the mutant SCSIO 24-2 in shake flasks. The results indicated that three medium components including mannitol, maltose, and L-cysteine had significant effects on OA production, and their concentrations were optimized as 36, 27.9, and 0.99 g/l, respectively. In the optimized medium, the OA production (18.31 ± 0.27 mg/l) by mutant SCSIO 24-2 was 4.4-fold higher than that in the basic medium. These results of this work promise to improve the present production of OA and may be adopted to enhance other objective products' production by marine-derived fungi.

Medium optimization for exopolysaccharide production in liquid culture of endophytic fungus Berkleasmium sp. Dzf12

Berkleasmium sp. Dzf12, an endophytic fungus from Dioscorea zingiberensis, is a high producer of spirobisnaphthalenes with various bioactivities. The exopolysaccharide (EPS) produced by this fungus also shows excellent antioxidant activity. In this study, the experimental designs based on statistics were employed to evaluate and optimize the medium for EPS production in liquid culture of Berkleasmium sp. Dzf12. For increasing EPS yield, the concentrations of glucose, peptone, KH(2)PO(4), MgSO(4)·7H(2)O and FeSO(4)·7H(2)O in medium were optimized using response surface methodology (RSM). Both the fractional factorial design (FFD) and central composite design (CCD) were applied to optimize the main factors which significantly affected EPS production. The concentrations of glucose, peptone and MgSO(4)·7H(2)O were found to be the main effective factors for EPS production by FFD experimental analysis. Based on the further CCD optimization and RSM analysis, a quadratic polynomial regression equation was derived from the EPS yield and three variables. Statistical analysis showed the polynomial regression model was in good agreement with the experimental results with the determination coefficient (adj-R(2)) as 0.9434. By solving the quadratic regression equation, the optimal concentrations of glucose, peptone and MgSO(4)·7H(2)O for EPS production were determined as 63.80, 20.76 and 2.74 g/L, respectively. Under the optimum conditions, the predicted EPS yield reached the maximum (13.22 g/L). Verification experiment confirmed the validity with the actual EPS yield as 13.97 g/L, which was 6.29-fold in comparison with that (2.22 g/L) in the original basal medium. The results provide the support data for EPS production in large scale and also speed up the application of Berkleasmium sp. Dzf12.