Isolation, Antimicrobial Activity, and Metabolites of Fungus Cladosporium sp. Associated with Red Alga Porphyra yezoensis
Cladosporium sp. isolate N5 was isolated as a dominant fungus from the healthy conchocelis of Porphyra yezoensis. In the re-infection test, it did not cause any pathogenic symptoms in the alga. Twenty-one cultural conditions were chosen to test its antimicrobial activity in order to obtain the best condition for large-scale fermentation. Phenylacetic acid, p-hydroxyphenylethyl alcohol, and l-ß-phenyllactic acid were isolated from the crude extract as strong antimicrobial compounds and they are the first reported secondary metabolites for the genus Cladosporium. In addition, the Cladosporium sp. produced the reported Porphyra yezoensis growth regulators phenylacetic acid and p-hydroxyphenylacetic acid. No cytotoxicity was found in the brine shrimp lethality test, which indicated that the environmental-friendly Cladosporium sp. could be used as a potential biocontrol agent to protect the alga from pathogens.
This work was supported by the National High Technology Research and Development Program of China (2007AA09Z412), and the Innovative Key Project of the Chinese Academy of Sciences (KZCX2-YW-209). We thank R. Machinek and H. Frauendorf for NMR and mass spectra respectively, and F. Lissy and A. Kohl for technical assistance. Many thanks to Prof. W. E. G. Müller, from Mainz University for his kind help in correction of this paper.
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