1,4-Disubstituted-1,2,3-triazole (Tz) is widely used in peptides as a trans-amide bond mimic, despite having hazardous effects on the native peptide activity. The impact of amide bond substitution by Tz on peptide secondary structures is scarcely documented. We performed a Tz scan, by systematically replacing peptide bonds following the Aib residues with Tz on two model peptaibols: alamethicin F50/5 and bergofungin D, which adopt stable α- and 3₁₀ helices, respectively. We observed that the Tz insertion, whatever its position in the peptide sequences, abolished their antimicrobial activity. The structural consequences of this insertion were further investigated using CD, NMR and X-ray diffraction. Importantly, five crystal structures that were incorporated with Tz were solved, showing various degrees of alteration of the helical structures, from minor structural perturbation of the helix to partial disorder. Together, these results showed that Tz insertions impair helical secondary structures.

A marine-derived strain of Clonostachys rosea isolated from sediments of the river Loire estuary (France) was investigated for its high lipid production. The fungal strain was grown on six different culture media to explore lipid production changes. An original branched conjugated fatty acid, mainly present in triglycerides and mostly produced when grown on DCA (23% of total fatty acid composition). It was identified as 4-Me-6E,8E-hexadecadienoic on the basis of spectroscopic analyses. This fatty acid reduced viability of MCF-7 breast cancer cells in a dose dependent manner (up to 63%) at physiological free fatty acid human plasma concentration (100 μM). Reduction of gene expression of two lipogenic enzymes, the acetyl CoA carboxylase (ACC) and the fatty acid synthase (FAS) was evaluated to explore the mechanisms of action of 4-Me-6E,8E-16:2 acid. At 50 μM, 50% and 35% of mRNA gene expression inhibition were observed for ACC and FAS, respectively.

The most common sterol in fungi is ergosterol, which has frequently been investigated in human pathogenic fungal strains. This sterol, and others isolated from fungal strains, has also demonstrated cytotoxicity against cancer cell lines and antimicrobial activities. Marine fungi can produce high amounts of bioactive compounds. So, a screening was performed to study sterol composition using GC/MS in 19 marine fungal strains and ergosterol was always the major one. One strain, Clonostachys rosea MMS1090, was selected due to its high amount of eburicol and a one strain many compounds approach was performed on seven culture media to optimize its production. After purification and structural identification by NMR, eburicol was assessed against four cancer cell lines, MCF-7, MDA-MB-231, NSCLC-N6-L16 and A549, and seven human pathogenic bacteria Staphylococcus aureus, Bacillus sp., Bacillus cereus, Listeria ivanovii, Escherichia coli, Citrobacter freundii and Salmonella spp. The most significant activity was cytotoxicity against MCF-7 cells (2 µM). This is the first report of such an accumulation of eburicol in the marine fungal strain C. rosea confirming its potential in the production of bioactive lipids.

R-phycoerythrin (R-PE) can be enzymatically extracted from red seaweeds such as Palmaria palmata. This pigment has numerous applications and is notably known as an antioxidant, antitumoral or anti-inflammatory agent. Enzymes secreted by P. palmata associated fungal strains were assumed to be efficient and adapted for R-PE extraction from this macroalga. The aim of the present study was to quantify both xylanolytic and cellulolytic activities of enzymatic extracts obtained from six Palmaria palmata derived fungal strains. Degradation of P. palmata biomass by fungal enzymatic extracts was also investigated, focused on soluble protein and R-PE extraction. Enzymatic extracts were obtained by solid state fermentation. Macroalgal degradation abilities were evaluated by measuring reducing sugar release using DNS assays. Soluble proteins and R-PE recovery yields were evaluated through bicinchoninic acid and spectrophotometric assays, respectively. Various enzymatic activities were obtained according to fungal isolates up to 978 U/mL for xylanase and 50 U/mL for cellulase. Enzymatic extract allowed high degrading abilities, with four of the six fungal strains assessed exhibiting at least equal results as the commercial enzymes for the reducing sugar release. Similarly, all six strains allowed the same soluble protein extraction yield and four of them led to an improvement of R-PE extraction. R-PE extraction from P. palamata using marine fungal enzymes appeared particularly promising. To the best of our knowledge, this study is the first on the use of enzymes of P. palmata associated fungi in the degradation of its own biomass for biomolecules recovery.