Isolation of marine fungi associated with Sarcophyton ehrenbergi and the effect of temperature on their production of secondary metabolites / Liu Yuanwei

Liu , Yuanwei (2023) Isolation of marine fungi associated with Sarcophyton ehrenbergi and the effect of temperature on their production of secondary metabolites / Liu Yuanwei. Masters thesis, Universiti Malaya.

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Abstract

Despite limited knowledge on their ecological functions, soft coral-derived fungi produce a range of bioactive secondary metabolites, and have an impact on a diverse microbiome. Little attention has been given to soft corals and their associated fungi in Malaysia, especially the secondary metabolites they produce. Increased seawater temperature has been found to promote pathogen growth and weaken coral disease resistance, thus shifting coral-fungi association. This study isolates and identifies four fungal strains, Aspergillus sydowii, Acrocalymma sp., Lindgomyces sp. and Phomatospora sp., from a population of soft coral Sarcophyton ehrenbergi collected off the waters of Port Dickson in the Straits of Malacca. In addition, Aspergillus sydowii and Acrocalymma sp. were incubated at 25°C, 30°C and 35°C for two weeks to investigate the effect of increased temperatures on secondary metabolites production. The fungal biomass was extracted in ethyl acetate to obtain crude extracts, which were then analysed by TLC, HPLC and Q-TOF LCMS. Findings revealed that increased temperatures negatively affected the biomass production of both species, while the highest yields of crude extract were recorded at 35°C for Aspergillus sydowii and at 30°C for Acrocalymma sp. HPLC profiles of both species indicate an overall reduction in peak detection with an increase in temperature, despite a few unique peaks recorded at specific temperatures. On the contrary, LCMS profiles indicate that total numbers of compounds from crude extracts of both species follow a similar pattern as temperature increases, whereas the highest numbers were recorded at 25°C for Aspergillus sydowii and at 35°C for Acrocalymma sp. Detailed analysis of chemical formulas of LCMS results shows that the majority of detected chemicals were primary metabolites, which could be the high sensitivity of Q- TOF LCMS. The investigation in secondary metabolites from soft coral-associated fungi under rising seawater temperature illustrated potential biological responses to seawater temperature rise.

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