Isolation and bioassay screening of fungal endophytes from North Atlantic marine macroalgae

Endophytic fungi of marine macroalgae and the bioactive chemicals they produce have not been widely explored or documented. In this study, fungal endophytes were isolated from four species of brown, three species of red, and two species of green marine algae collected from the Shetland Islands, UK. Sixty-four distinct endophytes were isolated, 36 of which were identified to the genus or species level, with the highest diversity of isolable fungi being obtained from the green algae. Extracts of fungal tissue and spent nutrient broth were prepared from each isolate and screened for bioactivity. Antimicrobial and larvicidal assays revealed that the extracts from 24 endophytes showed antifungal activity, 25 displayed activity against Gram-positive bacteria, 20 showed activity against Gram-negative bacteria, and 11 showed larvicidal activity.