抄録
The degradation of three kinds of oils such as alkylbenzene, A heavy oil and the Iranian heavy crude oil by a bacterial strain, Caulobacter sp., isolated from the sea water of Tokyo Bay was studied experimentally in the enriched seawater (ESW) medium. The alkylbenzene used in the present study is a mixture of n-hexylbenzene, n-heptylbenzene, n-nonylbenzene and n-pentadecane.
The maximum rate of degradation was observed after a lag period of 6 to 14 days and the bacteria were found to degrade the oils at the rates calculated to be in a range from 1.1x10-11 to 3.7x10-11 mg-oil/cell/hr for the alkyl-benzene, from 5.9 10-12 to 5.3x 10-11 mg-oil/cell/hr for A heavy oil and from 1.6 10-11 to 1.1 10-10 mg-oil/cell/hr for the Iranian heavy crude oil.
The fraction of degradation of the alkylbenzene attained to 100 percent in the low oil contents of the range below 200 mg-oil /l while the A heavy oil and the Iranian heavy crude oil were degraded at most in about 80 percent even at low oil contents.
The maximum degradation rate, rm mg-oil/l /hr, was correlated with the amount of the initial total oil per liter of ESW, S mg-oil/l, as expesssed by the following equation :rm = (rm)max(SS+Km)where (rm)max denotes the ultimate value of rm when the oil is added in large excess and Km is a saturated constant. The value of (rm)max and Km for the oils used in the present study were calculated to be as follows : in the case of alkylbenzene, (rm)max=12.3 mg-oil/l/hr and Km=950.8 mg-oil/l; in the case of the A heavy oil, (rm)max=7.63 mg-oil/l/hr and Km=1045 mg-oil/l; in the case of the Iranian heavy crude oil, (rm)max=7.25 mg-oil/l/hr and Km=496 mg-oil/l.
