الفهرس 
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Abstract
Eight bacterial strains designed as MAM-P1, MAM-P8, MAM-P13 and MAM-P14 (group A) were isolated from soil contaminated with crude petroleum oil from El Zytea-port, Suez Canal, Egypt. While bacterial strains MAM-P22, MAM-P25, MAM-P26 and MAM-P39 (group B) were isolated from soil contaminated with crude petroleum oil from Cairo Oil Refining Company, Mostrod, Qalyubia, Egypt. These bacterial isolates were evaluated for their ability to grow on HMW-PAHs (benz[a]anthracene, benzo[a]pyrene and Pyrene) as a sole carbon and energy source.
The ability of eight bacterial isolates to grow on different concentrations (500µM, 750 µM, 1000 µM, 1250 µM and 1500 µM) of HMW-PAHs (benz[a]anthracene, benzo[a]pyrene and Pyrene) was investigated by recording their growth and secretion of extracellular protein at zero time (initial) and after 3, 6, 9, 12, 15, 18 and 21days incubation period.
These bacterial isolates also degraded and utilized different concentrations [(525µM, 550µM, 610µM and 625µM) and (1025µM, 1050µM, 1210µM and 1225µM )] of HMW-PAHs mixtures [(B[a]P+Pyr) and (B[a]A+ B[a]P+Pyr)] respectively. Their ability to utilize HMW-PAHs was investigated by recording their growth and secretion of extracellular protein at zero time (initial) and after 3, 6, 9, 12, 15, 18 and 21days of incubation.
Best growing bacterial isolate on different concentrations of HMW-PAHs was isolate MAM-P8 as indicated by growth and extracellular protein concentration, in which its growth increased as concentration of HMW-PAHs increased, also its growth increased along incubation period (21 days).
The maximum growth of strain MAM-P8 was reached after 21 days of incubation at all concentrations of HMW-PAHs and also in mixtures of HMW-PAHs.
Degradation Percentage of B[a]A, B[a]P, Pyr and also HMW-PAHs mixtures was measured by using HPLC for most potent bacterial isolates (MAM-P1, MAM-P8 and MAM-P13).
from results of HPLC, strain MAM-P8 showed highest percentage of HMW-PAHs degradation, as results revealed that it degraded B[a]A at concentration 1500 µM by 22.2% while Pyr was degraded at 1000µM by 77%. In case of mixture (B[a]P and Pyr) strain MAM-P8 degraded pyr (600µM) and B[a]P (25µM) by 27% and 74% respectively, while in mixture (B[a]A, B[a]P and Pyr) strain MAM-P8 degraded B[a]A (600µM), Pyr (600µM) and B[a]P (25µM) by 66%, 65% and 73% respectively.
The determination of the degradation intermediates of B[a]A and Pyr have been investigated by GC/MS. The pathway of degradation was phthalic acid degradation route as indicated by the intermediates produced by strain MAM-P8. In case of mixtures(double and triple) The corner stone intermediates in degradation of Pyr, B[a]A and B[a]P were trans-4,4-dimethoxy-beta-methylchalcone and phthalic acid (phthalic acid monocyclohexyl ester, phthalic acid monobutyl ester and phthalic anhydride) and benzanthraquinone.
from 16S-rRNA analysis of isolate MAM-P8 it showed similarity of 99% to Bacillus altitudinis strain. So isolate MAM-P8 was identified as Bacillus altitudinis.
We concluded that:
1- All eight bacterial isolates were able to grow on different concentrations (500µM, 750 µM, 1000 µM, 1250 µM and 1500 µM) of HMW-PAHs (B[a]A, B[a]P and Pyr).
2- These bacterial isolates can also degrade different concentrations [(525 µM, 550 µM, 610µM and 625µM) and (1025µM, 1050µM, 1210µM and 1225µM )] of HMW-PAHs mixtures [(B[a]P+Pyr)and (B[a]A+ B[a]P+Pyr)].
3- Best growing bacterial isolate on different concentrations of HMW-PAHs was MAM-P8 as indicated by growth rate, extracellular protein concentration and percentage of degradation (from results of HPLC, MAM-P8 showed highest percentage of HMW-PAHs degradation).