| Coral symbiotic and epiphytic fungi and their metabolites have been studied actively. The products are diverse and rich in bioactivity. Nevertheless, the thermotolerant fungi in corals have not been reported. The heat-resistant coral fungus Aspergillus terreus C21-5B was identified, its physiological characteristics, and the antioxidant activities were studied to provide a basis for further research and utilization of the fungus. The strain was identified by morphological observation and 18S rRNA sequence analysis; The physiological characteristics of the strain were studied by measuring the colony diameter under the condition of different concentration of sea table salts, pH and temperature; the antioxidant activities of the strain were determined based on the scavenging rate of DPPH free radical and ABTS free radical; the active components of C21-5 metabolism were analyzed by thin layer chromatography and high performance liquid chromatography. The coral fungus C21-5B was identified as Aspergillus terreus. The study on its physiological characteristics showed that the concentration of sea table salt for the growth of C21-5B was 0.0%-20.0%, pH 2.0-12.0, and temperature 15-45 ℃. The optimum growth conditions were that the concentration of sea table salt was 0.5%-3.5%, pH 6.0-8.0, and temperature 35 ℃. The metabolite extracted with ethyl acetate of the fungus C21-5 had comparatively high antioxidant activity, and the EC50 of DPPH and ABTS free radicals were 0.113 mg/mL and 0.504 mg/mL, respectively. It was found adopting the analysis with thin layer chromatography and high performance liquid chromatography that there were somewhat more polar components of neutrality, including alkaloids, lipoid compound, reducing substances, flavonoids and aromatic amines. Aspergillus terreus C21-5B is a thermotolerant and facultative marine fungus, which has strong acid-base tolerance capacity, with abundant category of metabolites and obvious antioxidant activity, it has the potential of development and utilization. |
