Factors affecting biosurfactant production by oil degrading Aeromonas spp. isolated from a tropical environment.

An Aeromonas spp. was isolated from tropical estuarine water. The organism grew on crude oil and produced biosurfactant that could emulsify hydrocarbons. The peak growth and biosurfactant production was on the 8th day. The organism grew on a range of hydrocarbons that include crude oil and hexadecane while no growth was recorded on some hydrocarbons that include benzene. The biosurfactant produced by the organism emulsified a range of hydrocarbons with diesel (E24=65) as the best substrate and hexane (E24=22) as the poorest. After purification, the biosurfactant was found to contain about 38% carbohydrate and an unidentified lipid. No protein was present in the purified biosurfactant. Production of biosurfactant was highest in medium with glucose and lowest in the medium with diesel+acetate. Soybean was the best nitrogen source for biosurfactant production. The activity of the biosurfactant was enhanced optimally at NaCl concentration of 5%, pH of 8.0 and temperature of 40 degrees C. The biosurfactant retained 77% of its original activity after 120 min of exposure to heat at a temperature of 100 degrees C. Biosurfactant may be produced with this organism using non-hydrocarbon substrates such as glucose and soybean that are readily available and would not require extensive purification for use in food and pharmaceutical industries.

Ultrastructure of two oil-degrading bacteria isolated from the tropical soil environment.

Two oil-degrading bacteria identified as Pseudomonas aeruginosa and Micrococcus luteus were isolated from crude-oil-polluted soils in Nigeria. The organisms were grown on n-hexadecane and sodium succinate and then examined for the presence of hydrocarbon inclusions. Inclusion bodies were found in n-hexadecane-grown cells and were absent in succinate-grown cells. Formation of hydrocarbon inclusion bodies appears to be a general phenomenon among hydrocarbon utilizers.

Degradation of anthracene by bacteria isolated from oil polluted tropical soils.

Four bacteria, identified as Pseudomonas aeruginosa, Alcaligenes eutrophus, Bacillus subtilis and Micrococcus luteus were isolated from crude oil polluted soils using anthracene as the sole carbon and energy source. All the organisms utilized n-hexadecane, n-tetradecane, diesel oil, engine oil and naphthalene as sole carbon sources. None could utilize hexane, cycloheptane, xylene, benzene, toluene, phenol, fluoranthene,and kerosene as carbon sources. Highest cell density obtained with 0.1% (w/v) anthracene were 4.5 x 10(7) (cfu/ml), 8.6 x 10(6) (cfu/ml), 5.4 x 10(6) and 2.4 x 10(6) (cfu/ml) respectively, for P. aeruginosa, A. eutrophus, B. subtilis and M. luteus after 30 days incubation. Growth of the organisms on a Nigerian crude oil resulted in a residual oil concentration of 22.2%, 33.3%, 39.3%, 44% and 91.7% respectively, for P. aeruginosa, A. eutrophus, B. subtilis, M. luteus and the noninoculated control on the 14 th day. Ring fission enzymes of the meta pathway were detected in induced cells of P. aeruginosa and A. eutrophus while ortho pathway enzymes were detected in B. subtilis and M. luteus. P. aeruginosa and A. eutrophus had specific catechol-2,3-dioxygenase activities of 3.8 +/- 0.183 and 0.64 +/- 0.032 micromol/min x mg protein respectively while catechol-1,2-dioxygenase activities of 1.95 +/- 0.029 and 1.89 +/- 0.026 micromol/min x mg protein were detected in B. subtilis and M. luteus respectively. This work, highlights the capability of these unreported tropical strains of A. eutrophus, B. subtilis and M. luteus as anthracene degraders.