EFFECT OF BIOSURFACTANTS ON THE DEGRADATION OF SELECTED HYDROCARBONS BY PSEUDOMONAS AERUGINOSA

Document Type : Original Article

Authors

1 Department of Microbiology, Faculty of Pharmacy, University of Zagazig - Egypt

2 Department of Microbiology, Faculty of Pharmacy, Zagazig University , Egypt

Abstract

Thirty two of different bacterial strains including Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas lemoignei, Alcaligenes faecalis, Alcaligenes eutrophus and Bacillus subtilis degraded tetradecane, hexadecene, pristane and 2- methylnaphthalene hydrocarbons with different percent. Pseudomonas aeruginosa I strain was the best strains in degradation of hydrocarbons and the only strain produced biosurfactants. Biosurfactants were produced by the isolated Pseudomonas aeruginosa mainly at the beginning of stationary phase of growth. After 7 days of incubation in a non-hydrocarbon medium, about 10 ml of crude surfactant could be removed from 1000 ml of culture supernatant. Biosurfactants lowered the surface tension of water to 35 dyn/cm, achieved critical micelle concentration (CMC) at 20 µg/ml and exhibited an emulsifying activity of 315 U/ml. Addition of 100µg/ ml of concentrated biosurfactant increased the biodegradation. Addition of biosurfactant to culture medium improved biodegradation of tetradecane from 70% to 95%; pristane from 50% to 70%; hexadecene from 40% to 60% and 2- methylnaphthalene from 10 % to 20%. However, the inocula addition caused only 10% increase in percentage of tetradecane, hexadecene and pristane degradation and no increase in percentage of 2- methylnaphthalene biodegradation.

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