BIODEGRADATION OF USED LUBRICATING OIL BY MICROBES ISOLATED FROM PRISTINE SOIL ENVIRONMENT - O. P, Abioye; P, Agamuthu; A.R, Abdul Aziz (Malaysian Journal of Science, 2011)
The effect of ultraviolet radiation (UVR) on the growth, lipid content and fatty acid profile of the tropical microalga Chlorella vulgaris UMACC 001 was investigated under laboratory and natural UVR conditions. The Chlorella was exposed to 10 days of PAR+UVA+UVB (1.17 Wm-2), PAR+UVA (8.54 Wm-2) and PAR alone (42 µmolm-2s-1) in the laboratory study. The natural UVR study was carried out by exposing the cultures to the natural environment on the roof-top of the Institute of Graduate Studies Building, University of Malaya for 54 hours. The average levels of UVA radiation, UVB radiation and PAR irradiance over the exposure period ranged from 3.66 to 27.95 Wm-2, 1.61 to 16.50 Wm-2 and 282 to 1480 µmol m-2s-1, respectively. UVA radiation did not affect the growth of Chlorella vulgaris UMACC 001 in both the laboratory and natural UVR studies. In contrast, growth was adversely affected by UVB radiation in the laboratory study. UVB radiation is known to decrease the stability of D1 protein (the herbicide binding protein of chloroplasts) of the photosystem II reaction centre (PSII), affect rubisco activity, pigment composition as well as generate superoxide dismutase, all of which would reduce photosynthesis and growth. No significant difference was observed in the lipid content of the cultures exposed to UVR compared to PAR alone in both laboratory and roof-top (natural UVR) cultures. Chlorella vulgaris UMACC 001 exhibited different response in fatty acid profiles under laboratory condition compared to roof-top (natural UVR) cultures. In the laboratory condition, more saturated fatty acids (SFA) were produced in the cultures exposed to laboratory-produced UVB radiation compared to PAR alone, while more polyunsaturated fatty acids (PUFAs) were produced in the cultures exposed to natural UVB radiation compared to PAR alone. Kesan radiasi ultraungu ke atas pertumbuhan, kandungan lemak dan profil asid lemak bagi mikroalga tropika Chlorella vulgaris UMACC 001 telah disiasat dalam keadaan makmal dan semulajadi. Chlorella tersebut didedah kepada PAR+UVA+UVB (1.17 Wm-2), PAR+UVA (8.54 Wm-2) dan PAR persendirian (42 mol m-2s-1) selama 10 hari dalam kajian makmal. Kajian semulajadi radiasi ultraungu dijalankan dengan mendedahkan kultur tersebut kepada persekitaran semulajadi di atas bumbung bangunan Institut Penggajian Pascasiswazah, Universiti Malaya selama 54 jam. Paras purata radiasi UVA, UVB dan PAR dalam tempoh pendedahan radiasi ultraungu semulajadi adalah 3.66 hingga 27.95 Wm-2, 1.61 hingga 16.50 Wm-2 dan 282 hingga 1480 µmol m-2s-1, masing-masing. Tiada kesan radiasi UVA ke atas tumbesaran Chlorella vulgaris UMACC 001 dalam kedua-dua eksperimen makmal dan semulajadi. Sebaliknya tumbesaran mikroalga tersebut menurun dengan ketara apabila didedahkan kepada radiasi UVB di dalam makmal. Diketahui bahawa radiasi UVB mengurangkan kestabilan protein D1 dalam fotosistem II (PSII), mempengaruhi aktiviti rubisco, komposisi pigment dan menghasilkan radikal superoxide yang mana semua akan mengurangkan fotosintesis dan tumbesaran. Tiada perbezaan ketara diperhatikan dalam kandungan lemak bagi kultur yang didedahkan kepada radiasi ultraungu berbanding dengan PAR persendirian dalam kedua-dua kajian makmal dan semulajadi. Chlorella vulgaris UMACC 001 menunjukkan tindak balas yang berbeza dalam profil asid lemak apabila kultur tersebut didedahkan kepada radiasi ultraungu dalam keadaan makmal dan semulajadi. Dalam keadaan makmal, lebih banyak asid lemak tepu (SFA) dihasilkan dalam kultur yang didedahkan kepada radiasi UVB berbanding dengan PAR persendirian, tetapi lebih banyak asid lemak poli tidak tepu (PUFAs) dihasilkan dalam kultur yang didedahkan kepada radiasi ultraungu-B semulajadi berbanding dengan PAR persendirian di atas bumbung (radiasi ultraungu semulajadi).