Ulva sp.

Noor, Sadia, Begum, Mst. Nadira, Rony, Satyajit Roy, Uddin, Mohammad Zashim, Sohrab, Md. Hossain & Mazid, Md. Abdul, 2024, Bioactivity and chemical screening of endophytic fungi associated with the seaweed Ulva sp. of the Bay of Bengal, Bangladesh, Botanica Marina (Warsaw, Poland) 67 (2), pp. 115-129 : 116

2.2 Isolation of endophytic fungi associated with Ulva sp.

The technique used by Chowdhury et al. (2016) was modified to isolate endophytic fungi from Ulva sp. To remove sand and adhering debris, the seaweed samples were coarsely washed with seawater from the collection site before being transported and processed in the lab within the shortest possible time. The seaweed samples were then subjected to surface sterilization, i.e., immersion of samples in ethanol (EtOH, 70 %), sodium hypochlorite solution (NaOCl, 5 %), and finally in EtOH (70 %) sequentially taking 1–2 min in each solution. To eliminate EtOH residues, all algal samples were then washed three times with sterile water. The selected samples were divided aseptically into small pieces (1–1.5 cm long), which were then put on the culture media supplemented with streptomycin sulphate (100 mg l −1, to suppress bacterial contamination), and then incubated at room temperature in the dark. A few positive controls (media with unsterilized algal samples), a few negative controls (media without any algal samples) and some imprints of sterilized algal samples on the culture media were also incorporated to detect endophytic fungi and to test the effectiveness of the surface sterilization process. The culture medium was prepared by dissolving agar (16 g l −1) in artificial seawater ( Nagano et al. 2009; Robinson 1954) and autoclaving at 121 ° C for 15 min. The hyphal tips that developed on the initial cultures were transferred to potato dextrose agar ( PDA). Pure cultures of the isolated endophytic fungi were then obtained by serial dilution or streaking methods ( Fergus 1964).