Identification Of An Endophytic Fungus, Aspergillus Terreus Mp15 Isolated From Swietenia Macrophylla Leaves With Antibacterial And Antioxidant Activities
| dc.contributor.author | Chan, Olivia Jade Yin | |
| dc.date.accessioned | 2016-10-24T03:36:25Z | |
| dc.date.available | 2016-10-24T03:36:25Z | |
| dc.date.issued | 2015-11 | |
| dc.description.abstract | This research was aimed to study the antimicrobial activity of the endophytic fungi previously isolated from the leaves of Swietenia macrophylla King. In the primary screening, one out of nine endophytic fungal isolates exhibited antimicrobial activity against at least one of the tested microorganisms. This fungal isolate was selected for further tests and was then identified as Aspergillus terreus based on its cultural features and molecular sequences. Based on the result obtained from the disc diffusion assay, the ethyl acetate extract (extracellular) of this fungal isolate showed promising and stable antibacterial activity against all the tested Gram positive bacteria. The zones of inhibition recorded were ranged from 10.3 ± 0.4 to 13.7 ± 0.6 mm, whilst minimal inhibitory concentration (MIC) ranged from 0.75 to 2.00 mg/mL and minimal bactericidal concentration (MBC) ranged from 2.00 to 8.00 mg/mL. The extract was bactericidal against Bacillus subtilis, Bacillus spizizenii and Staphylococcus aureus, while bacteriostatic against Bacillus cereus. Furthermore, the addition of host plant extract in the fermentation broth had no significant effect on the antibacterial activities of the endophytic fungal isolate, suggesting that it may have its own biosynthetic pathway to produce bioactive compounds. Besides, time kill study revealed that the antibacterial activity of the ethyl acetate extract was concentration dependant towards S. aureus. Moreover, starting at the 4th hour of treatment, the bacterial cells were completely killed with MIC without any regrowth in subsequent hours. The significant bactericidal effect of extract against S. aureus was also evidenced when viewed under scanning electron microscope. The bacterial cells were collapsed, no longer in coccal shape and there were formation of cavities on the cell surfaces. On the other hand, this A. terreus MP15 extract exhibited potential antioxidant activity and also consisted of high total phenolic content. Furthermore, on bioautography assay, it revealed that a yellow spot with retention factor, Rf value 0.52 from this extract contributed to the antibacterial activity. Subsequently, the yellow fraction labeled as 2a of the extract exhibited more potent antibacterial activity as the MIC and MBC values were lowered, both ranged from 0.25 to 0.50 mg/mL. Besides, brine shrimp toxicity test also demonstrated that the fraction was non-toxic. The gas chromatography-mass spectrometry analysis of this yellow fraction revealed that the major compound was di-n-octyl phthalate, which may contribute to the antibacterial and antioxidant activities of the extract. Therefore, the extract of A. terreus MP15 can be regarded as a safer and potential source as antibacterial and antioxidant food preservatives, as well as yellow colorant. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/2810 | |
| dc.language.iso | en | en_US |
| dc.publisher | Universiti Sains Malaysia | en_US |
| dc.subject | Endophytic Fungus | en_US |
| dc.title | Identification Of An Endophytic Fungus, Aspergillus Terreus Mp15 Isolated From Swietenia Macrophylla Leaves With Antibacterial And Antioxidant Activities | en_US |
| dc.type | Thesis | en_US |
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