Samir S. Radwan

Crude oil and hydrocarbon-degrading strains of Rhodococcus rhodochrous isolated from soil and marine environments in Kuwait

Soil and marine samples collected from different localities in Kuwait were screened for microorganisms capable of oil degradation. Both fungi and bacteria were isolated. The fungal flora consisted of Aspergillus terreus, A. sulphureus, Mucor globosus, Fusarium sp. and Penicillum citrinum. Mucor globosus was the most active oil degrading fungus isolated. Bacterial isolates included Bacillus spp. Enterobacteriaceae, Pseudomonas spp., Nocardia spp., Streptomyces spp.,and Rhodococcus spp. Among these Rhodococcus strains were the most efficient in oil degradation and, relatively speaking, the most abundant. Bacterial and fungal isolates differed in their ability to degrade crude oil, with Rhodococcus isolates being more active that fungin in n-alkane biodegradation, particularly in the case of R. rhodochrous. In addition to medium chain n-alkanes, fungi utilized one or more of the aromatic hydrocarbons studied, while bacteria failed to do so. R. rhodochorous KUCC 8801 was shown by GLC and post-growth studies to be more efficient in oil degradation than isolates known to be active oil degraders.

High-temperature hydrocarbon degradation by Bacillus stearothermophilus from oil-polluted Kuwaiti desert

Kuwaiti desert samples contaminated with crude oil contained Bacillus stearothermophilus strains capable of growth on crude oil as a sole source of carbon and energy, obligately at high temperature. No thermophilic oil utilizers were present in water samples collected from the Arabian Gulf. Most of the desert strains had an optimum temperature of 60°C and grew best on pentadecane (C15), hexadecane (C16) and heptadecane (C17). n-Alkanes with shorter and longer chains, n-alkenes, and aromatic hydrocarbons were less readily utilized.

Sources of C20-polyunsaturated fatty acids for biotechnological use

SummaryPolyunsaturated fatty acids with 20 carbon atoms exhibit unique physiological activities in the human body, for example lowering of cholesterol and triacylglycerols in plasma, prevention of atherosclerosis and other cardiovascular diseases and reduction of colagen-induced thrombocyte aggregation. Moreover, these fatty acids are of great value in the nutrition of edible marine animals reared in mariculture, and as precursors of eicosanoid hormones. Potential sources of such fatty acids include fungi, mainly lower Phycomycetes, microalgae, viz. dinoflagellates, diatoms and unicellular red algae, marine macroalgae, particularly Phaeophyta and Rhodophyta, and mosses. The biomass may be enriched with C20-polyunsaturated fatty acids by chilling, nitrogen starvation, controlled illumination and incubation with lipophilic compounds.

Rhizospheric hydrocarbon-utilizing microorganisms as potential contributors to phytoremediation for the oily Kuwaiti desert.

Roots of the wild desert plants, Senecio glaucus, Cyperus conglomeratus, Launaea mucronata, Picris babylonica and Salsola imbricata and the crop plants Vicia faba and Lupinus albus grown in oil polluted and clean soils were densely associated with hydrocarbon utilizing bacteria. The most dominant were Cellulomonas flavigena, Rhodococcus erythropolis and Arthrobacter sp. The rhizosphere soils of all plants contained more hydrocarbon-utilizers than the soils apart. This rhizosphere effect was much more pronounced for plants growing in oil-polluted than clean soils. C. flavigena predominant in the rhizosphere of Vicia faba took up representative test aliphatic and aromatic hydrocarbons. Thus, these bacteria could be contributing in nature to detoxifying and bioremediating the soil around the roots. It was concluded that vegetation may be a feasible approach for cleaning oil-polluted soil, including the polluted Kuwaiti desert areas.

Soil management enhancing hydrocarbon biodegradation in the polluted Kuwaiti desert

Oil-polluted Kuwaiti desert samples, exposed to the open air, were subjected to specific types of management, once every 2 weeks, throughout a year; control samples were not treated. The total amounts of extractable alkanes from the control samples remained fairly constant during the dry hot months, but decreased during the rainy months reaching, after 1 year, slightly more than one-half of the amount at zero time. This result demonstrates the self-cleaning of the Kuwaiti desert and the essential role of moisture in this process. Out of the eight types of management studied, the repeated fertilization of the polluted sample with 3% KNO3 solution was most efficient, reducing the extractable alkanes after 1 year to about one-third of zero reading. Repeated fertilization with treated sewage effluent was inhibitory to alkane biodegradation, probably because of increasing soil acidity. The latter inhibitory effect was annulled by liming. Repeated irrigation with 3% NaCl solution was inhibitory, but 1% NaCl solution slightly promoted alkane biodegradation. The various samples contained 1010–1011 oil-utilizing bacteria/g soil, predominantly Bacillus, Pseudomonas, Rhodococcus and Streptomyces. Oil-utilizing fungi were much less frequent and were predominantly Aspergillus and Penicillium species. The microbial numbers varied not only according to the type of soil management but also to the season.

Bioremediation of oily sea water by bacteria immobilized in biofilms coating macroalgae

Abstract Using the standard plate method and a solid mineral medium containing crude oil as a sole source of carbon and energy, 10 different macroalgae from the Arabian Gulf were found associated with large numbers of oil-utilizing bacteria. Each gram fresh alga was associated with about two to about 30 million cells of bacteria predominantly belonging to the nocardioforms and the genus Acinetobacter . Shaking macroalgal samples in sea water batches containing known amounts of individual hydrocarbons led to considerable attenuation of these compounds as measured by GLC. Thus, bacteria associated with macroalgae consumed about 64–98% of n- octadecane and about 38–56% phenanthrene from medium aliquots containing 0.03% of the test hydrocarbon after 2 weeks. Meanwhile, the oil-utilizing bacteria, especially the nocardioforms, associated with the macroalgae increased in number by about 32–490 fold, depending on the macroalgae and hydrocarbons studied. On the other hand, relatively negligible numbers of bacteria were released into the sea water compared with the numbers immobilized on the macroalgal surfaces. Individual bacterial isolates could grow on a wide range of pure alkanes and aromatic hydrocarbons as sole sources of carbon and energy. It was concluded that macroalgae submerged in the sea waters are coated with biofilms rich in oil-utilizing bacteria, that contribute to hydrocarbon attenuation in water. These natural biological consortia represent valuable tools that could be of high potential for phytoremediation of oily sea water.

Utilization of hydrocarbons by cyanobacteria from microbial mats on oily coasts of the Gulf

Several pieces of evidence indicate that Microcoleu chthonoplastes and Phormidium corium, the predominant cyanobacteria in microbial mats on crude oil polluting the Arabian Gulf coasts, contribute to oil degradation by consuming individual n-alkanes. Both cyanobacteria grew phototrophically better in the presence of crude oil or individual n-alkanes than in their absence, indicating that hydrocarbons may have been utilized. This result was true when growth was measured in terms of dry biomass, as well as in terms of the content of biliprotein, the accessory pigment characteristic of cyanobacteria. The phototrophic biomass production by P. corium was directly proportional to the concentration of n-nonadecance (C19) in the medium. The chlorophyll to carotene ratio of hydrocarbon-grown cyanobacteria did not decrease compared to the ratio in the absence of hydrocarbons, indicating that on hydrocarbons the organisms were not stressed. Comparing the fatty acid patterns of total lipids from hydrocarbon-grown cyanobacteria to those of the same organisms grown without hydrocarbons confirms that n-alkanes were taken up and oxidized to fatty acids by both cyanobacteria.

Lipids of n-Alkane-Utilizing Microorganisms and Their Application Potential

Publisher Summary This chapter describes the lipids of n -Alkane-utilizing microorganisms and their application potential. The chapter refers the potential commercial values of various lipid classes and fatty acids. In addition, reference is made to environmental considerations associated with the proposed application of microorganisms in controlling oil pollution and in enhanced oil recovery. That lipids of n -alkaline-utilizing microorganisms should be expected to differ from the lipids of the same organisms grown on conventional substrates is apparent from the following arguments. (1) n -Alkanes, being water insoluble, expectedly induce in cell membranes alterations that allow for their enhanced active transport. Such alterations may involve the membrane lipids which contribute to about 50% of the membrane weight. )2) Alkanes, themselves lipids, are taken up, chemically unchanged, and thus directly contribute to the total cell lipids. (3) Initial phases of n -alkane metabolism involve the oxidation of these substrates to fatty alcohols and fatty acids that become, in part, incorporated into complex cell lipid compounds. (4) Several n -alkane-utilizing microorganisms reveal cytological entities that are associated with their growth on n -alkanes as substrates. Thus, certain bacteria produce intracytoplasmic membranes, and yeasts produce peroxisomes. Like other biological membranes and organelles, these cytological entities are expected to be rich in lipids.

The potential of oil-utilizing bacterial consortia associated with legume root nodules for cleaning oily soils

The surfaces of root nodules of Vicia faba and Lupinus albus (legume crops), were colonized with bacterial consortia which utilized oil and fixed nitrogen. Such combined activities apparently make those periphytic consortia efficient contributors to bioremediation of oily nitrogen-poor desert soils. This was confirmed experimentally in this study. Thus, cultivating V. faba, L. albus and, for comparison, Solanum melongena, a nonlegume crop, separately in oily sand samples resulted in more oil attenuation than in an uncultivated sample. This effect was more pronounced with the legume crops than with the nonlegume crop. Furthermore, in flask cultures, V. faba plants with nodulated roots exhibited a higher potential for oil attenuation in the surrounding water than plants with nodule-free roots. Denaturation gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified 16S rRNA coding genes revealed that periphytic bacteria had DGGE bands not matching those of the oil-utilizing rhizospheric bacteria. Legume nodules also contained endophytic bacteria whose 16S rDNA bands did not match those of Rhizobium nor those of all other individual periphytic and rhizospheric strains. It was concluded that legume crops host on their roots bacterial consortia with a satisfactory potential for oil phytoremediation.

Oil Pollution and Cyanobacteria

There is increasing evidence that ancient cyanobacteria were among the direct biogenic contributors to oil formation. This fact underlines the historical and ecological relations between these photosynthetic microorganisms and petroleum. Evidence that cyanobacteria are capable of hydrocarbon degradation is tentative, but preliminary studies indicate that some strains are capable of oxidizing aromatic and aliphatic oil constituents. Further, in cyanobacterial-dominated mats, the cyanobacteria live in natural association with hydrocarbon-degrading bacteria and fungi that occur in the cyanobacterial polysaccharide layers. Such mat associations flourish in oil-polluted coastal areas of subtropical regions like the Arabian Gulf. The combined activities of the cyanobacteria and the associated oil-degrading organotrophs appear to be crucial and effective in bioremediating such polluted environments.