Gideon C. Okpokwasili

Monitoring of microbial hydrocarbon remediation in the soil

Bioremediation of hydrocarbon pollutants is advantageous owing to the cost-effectiveness of the technology and the ubiquity of hydrocarbon-degrading microorganisms in the soil. Soil microbial diversity is affected by hydrocarbon perturbation, thus selective enrichment of hydrocarbon utilizers occurs. Hydrocarbons interact with the soil matrix and soil microorganisms determining the fate of the contaminants relative to their chemical nature and microbial degradative capabilities, respectively. Provided the polluted soil has requisite values for environmental factors that influence microbial activities and there are no inhibitors of microbial metabolism, there is a good chance that there will be a viable and active population of hydrocarbon-utilizing microorganisms in the soil. Microbial methods for monitoring bioremediation of hydrocarbons include chemical, biochemical and microbiological molecular indices that measure rates of microbial activities to show that in the end the target goal of pollutant reduction to a safe and permissible level has been achieved. Enumeration and characterization of hydrocarbon degraders, use of micro titer plate-based most probable number technique, community level physiological profiling, phospholipid fatty acid analysis, 16S rRNA- and other nucleic acid-based molecular fingerprinting techniques, metagenomics, microarray analysis, respirometry and gas chromatography are some of the methods employed in bio-monitoring of hydrocarbon remediation as presented in this review.

Bioremediation techniques–classification based on site of application: principles, advantages, limitations and prospects

Environmental pollution has been on the rise in the past few decades owing to increased human activities on energy reservoirs, unsafe agricultural practices and rapid industrialization. Amongst the pollutants that are of environmental and public health concerns due to their toxicities are: heavy metals, nuclear wastes, pesticides, green house gases, and hydrocarbons. Remediation of polluted sites using microbial process (bioremediation) has proven effective and reliable due to its eco-friendly features. Bioremediation can either be carried out ex situ or in situ, depending on several factors, which include but not limited to cost, site characteristics, type and concentration of pollutants. Generally, ex situ techniques apparently are more expensive compared to in situ techniques as a result of additional cost attributable to excavation. However, cost of on-site installation of equipment, and inability to effectively visualize and control the subsurface of polluted sites are of major concerns when carrying out in situ bioremediation. Therefore, choosing appropriate bioremediation technique, which will effectively reduce pollutant concentrations to an innocuous state, is crucial for a successful bioremediation project. Furthermore, the two major approaches to enhance bioremediation are biostimulation and bioaugmentation provided that environmental factors, which determine the success of bioremediation, are maintained at optimal range. This review provides more insight into the two major bioremediation techniques, their principles, advantages, limitations and prospects.

Drilling fluid base oil biodegradation potential of a soil Staphylococcus species

Staphylococcus sp. isolated from oil-contaminated soil was grown in 1% drilling fluid base oil, HDF- 2000, as a sole source of carbon and energy. The organism has strong affinity for the substrate, growing at the rate of 0.16 h-1. It uses adherence and emulsification as mechanisms for oil uptake. In a nutrient-rich marine broth, base oil (up to 2.0% v/v) and glucose (up to 1.6% w/v) have no significant effect on the growth rates. This showed that the Staphylococcus sp. is a strong primary utilizer of the base oil and has potential for application in bioremediation processes involving oil-based drilling fluids. Key words : Drilling fluid base oil, Staphylococcus sp., biodegradation African Journal of Biotechnology Vol.2(9) 2003: 293-295

Seasonal ecology of hydrocarbon-utilizing microbes in the surface Waters of a river

Seasonal changes in the microbial communities of the New Calabar Riverwater have been investigated. Analyses of the BOD, pH, salinity, oil and grease levels of effluents of industries sited along the river were also conducted. High hydrocarbon-utilizing microbial populations were found. The percentage of hydrocarbon-utilizing heterotrophic bacteria ranged between 0–98% and 0–68% in the rainy and dry months, respectively. Counts of hydrocarbon-utilizing actinomycetes in the rainy months ranged between 0–95% and 2–55% in the dry months. The hydrocarbon-utilizing yeast population ranged between 1–95% and 2–85% for the rainy and dry months, respectively. Rainy month values for hydrocarbon-utilizing mould population ranged from 0–17% while dry month values ranged from 0–47%. The hydrocarbon-utilizing cyanobacterial population ranged between 0–95% and 0–33% in the rainy and dry months, respectively. Our results suggest that the heterotrophic bacterial and cyanobacterial populations are higher in the rainy months than in the dry months. However, the hydrocarbon-utilizing yeast, mould and actinomycete populations did not show seasonal variation.

SEASONAL INFLUENCES OF THE ORGANIC POLLUTION MONITORING OF THE NEW CALABAR RIVER, NIGERIA

Monitoring of the New Calabar River water was conductedmonthly for a period of one year to ascertain seasonalinfluences and industrial effluent discharges on the organicpollution status of the river. Dissolved oxygen (DO) levelsranged between 3.4 and 9.1 mg/l and 4.4–9.0 mg/l for therainy and dry seasons respectively. Total dissolved solids(TDS) levels ranged between 6.5 and 4013.9 mg/l for the rainyseason and 4.32–619.5 mg/l for the dry season. The ranges forthe organic pollutant parameters were: biochemical oxygendemand, 0.25–4.20 mg/l and 0.15–4.95 mg/l; COD, 10–1000mg/l and 15–100 mg/l; oil and grease, 0.00001–5000 μg/l and0.00001–800 μg/l; anionic surfactants, 2.0–30 μgMBAS/l and 0.1–2.0 μg MBAS/l for the rainy and dryseasons respectively. The ranges for the same parameters forthe industrial effluent were: DO, 2.1–3.9 mg/l and 6.5–10.8mg/l; BCD, 0.35–1.4 mg/l and 2.3–2.7 mg/l; COD, 508 mg/l and20–576 mg/l; oil and grase, 0.07–50 μg/l and0.048–25.0 μg/l; and anionic surfactants, 4.0–7.3μg MBAS/l and 0,2–17.0 μg MBAS/l for the rainyand dry seasons respectively. These results indicate thatseasonal changes as well as industrial effluent dischargesinfluenced the organic load of the river.

Primary biodegradation of antionic surfactants in laundry detergents

Abstract Microbial degradation of surfactant components of five powdered laundry detergents and sodium dodecyl sulphate (SDS) was investigated. Biodegradation was evaluated by monitoring substrate disappearance in terms of methylene blue active substances (MBAS) using “river — water die-away” method. While SDS and three commercial detergents were degraded in 21 days or less, two persisted for 28 days or more. One of them was only 45% degraded in 32 days.

Dynamics of indigenous bacterial communities associated with crude oil degradation in soil microcosms during nutrient-enhanced bioremediation.

Bacterial population dynamics were examined during bioremediation of an African soil contaminated with Arabian light crude oil and nutrient enrichment (biostimulation). Polymerase chain reaction followed by denaturing gradient gel electrophoresis (DGGE) were used to generate bacterial community fingerprints of the different treatments employing the 16S ribosomal ribonucleic acid (rRNA) gene as molecular marker. The DGGE patterns of the nutrient-amended soils indicated the presence of distinguishable bands corresponding to the oil-contaminated–nutrient-enriched soils, which were not present in the oil-contaminated and pristine control soils. Further characterization of the dominant DGGE bands after excision, reamplification and sequencing revealed that Corynebacterium spp., Dietzia spp., Rhodococcus erythropolis sp., Nocardioides sp., Low G+C (guanine plus cytosine) Gram positive bacterial clones and several uncultured bacterial clones were the dominant bacterial groups after biostimulation. Prominent Corynebacterium sp. IC10 sequence was detected across all nutrient-amended soils but not in oil-contaminated control soil. Total heterotrophic and hydrocarbon utilizing bacterial counts increased significantly in the nutrient-amended soils 2 weeks post contamination whereas oil-contaminated and pristine control soils remained fairly stable throughout the experimental period. Gas chromatographic analysis of residual hydrocarbons in biostimulated soils showed marked attenuation of contaminants starting from the second to the sixth week after contamination whereas no significant reduction in hydrocarbon peaks were seen in the oil-contaminated control soil throughout the 6-week experimental period. Results obtained indicated that nutrient amendment of oil-contaminated soil selected and enriched the bacterial communities mainly of the Actinobacteria phylogenetic group capable of surviving in toxic contamination with concomitant biodegradation of the hydrocarbons. The present study therefore demonstrated that the soil investigated harbours hydrocarbon-degrading bacterial populations which can be biostimulated to achieve effective bioremediation of oil-contaminated soil.

Tolerance of Nitrobacter to toxicity of hydrocarbon fuels

The effects of four hydrocarbon fuels (jet fuel, kerosene, gasoline and diesel oil) on the nitrite utilization and logarithmic rate of growth of Nitrobacter were investigated. Nitrite utilization was determined by coupling of diazotised sulfanilic acid with naphthylamine hydrochloride. Nitrite utilization increased with increase in exposure period to the fuels. Low fuel concentrations proved stimulatory while high concentrations were inhibitory to the nitrification process. The percent-log survival of Nitrobacter decreased with increase in exposure time and concentration of the fuels. Nitrobacter sensitivity to hydrocarbon fuels decreased in the order, kerosene > jet fuel = gasoline > diesel oil.

Response of Nitrobacter to toxicity of drilling chemicals

The effect of drilling chemicals on nitrate utilization and logarithmic rate of growth of Nitrobacter was investigated using varying concentrations of the chemicals. Results indicated that all the drilling chemicals tested were inhibitory to nitrate utilization and caused decrease in growth rate of Nitrobacter. An increase in nitrite utilization by Nitrobacter with increase in exposure time to the chemicals was observed. Nitrite utilization decreased with increase in concentration of the chemicals. Some concentrations of drilling chemicals stimulated the growth rate of Nitrobacter as exposure time increased. Inhibition of nitrite utilization was greatest with Carbotrol and least with Chaux (lime) and Huile-clean. These results showed that drilling chemicals inhibit an aspect of nitrification in the biosphere thereby negatively affecting soil and water fertility.

Biodeterioration Abilities of Microorganisms in Brake Fluids

Aims: To identify the parameters that get affected when brake fluids biodeteriorate and also to make known that brake fluids biodeteriorates into novel compounds. To also identify the organisms that deteriorates brake fluids most.