Chee , Mei Sing
(2010)
Effect Of Crude Aldehyde Dehydrogenase
On The Degradation Of Crude Oil By A
Local Isolate, Acinetobacter Baumannii
Fetl C4.
Masters thesis, Universiti Sains Malaysia.
Abstract
Detection of hydrocarbon-degrading enzymes activities in microorganisms capable
of utilizing crude oil as a carbon source were done using potential oil-degraders
isolated from soil and water samples collected from water and oil-contaminated
areas in Penang. Seven potential isolates categorized as Group I bacteria were
selected based on the criteria that they displayed good growth on solid crude oil
medium using 6 different types of crude oil which were named as. Tapis, Khefji
Dubai, Bunga Kekwa, Angsi, Dulang, and Penara. These crude oil media were
prepared without the addition of surfactant. Out of seven isolates, oil-degrading
bacterium designated as FETL C4 displayed good growth on different types of crude
oil media prepared. Biochemical test results identified this isolate as Acinetobacter
sp. Further confirmation was done using 16S rRNA gene analysis and Remel Rapid
Identification Kit. Aldehyde dehydrogenase (ALDH) activity was detected during
the cultivation of this isolate when grown in minimal salt medium containing 1%
(w/v) Tapis crude as a carbon source. Optimizations on the production of this
enzyme were done by manipulating physical and chemical parameters of the growth
and enzyme production. The optimization process were carried out in a flask system
(250 mL) and then further scaled up via fermenter system (5 L). Cells were
harvested from the growth medium when maximum points were reached for both
enzyme activity and degradation of the crude oil. The optimal conditions when
aldehyde dehydrogenase activity detected at the highest rate were obtained at 0.2 giL
(NH4)2S04, 0.4 giL KH2P04, 0.8 giL Na2HP04, 1.0 giL Tapis crude, 0.2 giL Tween
80 as surfactant, cultivation temperature at 37°C, initial medium pH 8.0, with
addition of 5% inoculum (1 x 106 cells/mL) and agitated at 600 rpm. Aeration rate
was set at 2L per minute to enhance the growth of the isolate. Biomass production
and degradation rate of the crude oil were 2.0 giL and 70%, respectively.
Zymogram analysis of aldehyde dehydrogenase on different aldehyde substrates
revealed that only one activity band that involved in the metabolism of various
aldehyde substrates. Quantitative analysis of this enzyme on different aldehyde
substrates showed a higher preference towards aldehyde with carbon 12.
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