Effects of Zeolite-Containing Material and Ammonium Nitrate on Biodegradation of n-Tridecane in Heavy Clay-Loam Leached Chernozem with High Organic Matter Content

Biostimulation based on usage of soil amendments is growing due to their efficiency in removing different petroleum hydrocarbons (PHC) from contaminated sand or loam-sand soils. However, the research on clay-rich soils with higher organic carbon content, in which PHC biodegradation may proceed differently and which are more difficult to clean up, has been less extensive. In a pot experiment, we studied and compared the effects of two soil amendments, natural zeolite-containing material (ZCM, 50 g kg^?1) as a bulking agent and ammonium nitrate (0.3 g N kg^?1) as a nitrogen fertilizer, on biodegradation of n-tridecane (1 wt.%) in a weakly acidic heavy clay loam leached chernozem with fairly high organic carbon content (3.71%). After 48 days, the nitrogen-amended contaminated soil showed enhancement of both respiratory activity (basal and substrate-induced respiration rates) and the number of n-tridecane- degraders. As a consequence, the extent of n-tridecane biodegradation (86.5%) was essentially higher in the presence of added nitrogen than that in the non-amended soil (73.7%). In contrast, due to the partial retention of n-tridecane molecules in its pores, ZCM retarded biodegradation to 56.0%, showed no significant effect on the number of n-tridecane-degraders and, moreover, enhanced the decomposition of the soil intrinsic organic matter. The obtained data indicate that more precautions should be considered when using porous sorbents such as ZCM for remedial arrangements in PHC-contaminated soils.     

Stimulation of Diesel Fuel Biodegradation by Indigenous Nitrogen Fixing Bacterial Consortia

Abstract Successful stimulation of N₂ fixation and petroleum hydrocarbon degradation in indigenous microbial consortia may decrease exogenous N requirements and reduce environmental impacts of bioremediation following petroleum pollution. This study explored the biodegradation of petroleum pollution by indigenous N₂ fixing marine microbial consortia. Particulate organic carbon (POC) in the form of ground, sterile corn-slash (post-harvest leaves and stems) was added to diesel fuel amended coastal water samples to stimulate biodegradation of petroleum hydrocarbons by native microorganisms capable of supplying a portion of their own N. It was hypothesized that addition of POC to petroleum amended water samples from N-limited coastal waters would promote the growth of N₂ fixing consortia and enhance biodegradation of petroleum. Manipulative experiments were conducted using samples from coastal waters (marinas and less polluted control site) to determine the effects of POC amendment on biodegradation of petroleum pollution by native microbial consortia. Structure and function of the microbial consortia were determined by measurement of N₂ fixation (acetylene reduction), hydrocarbon biodegradation (¹⁴C hexadecane mineralization), bacterial biomass (AODC), number of hydrocarbon degrading bacteria (MPN), and bacterial productivity (³H-thymidine incorporation). Throughout this study there was a consistent enhancement of petroleum hydrocarbon degradation in response to the addition of POC. Stimulation of diesel fuel biodegradation following the addition of POC was likely attributable to increases in bacterial N₂ fixation, diesel fuel bioavailability, bacterial biomass, and metabolic activity. Toxicity of the bulk phase water did not appear to be a factor affecting biodegradation of diesel fuel following POC addition. These results indicate that the addition of POC to diesel-fuel-polluted systems stimulated indigenous N₂ fixing microbial consortia to degrade petroleum hydrocarbons. Received: 29 December 1998; Accepted: 6 April 1999     

Biostimulation of n-Alkane Degradation in Diesel Fuel-Spiked Soils

Nutrient enhancement of bioremediation with nitrogen, namely biostimulation, increases process performance. Selection of a proper nitrogen source is critical for bioremediation applications. In this study, the effects of different nitrogen sources on biodegradation of C₁₀–C₂₅ n-alkane compounds in diesel fuel-spiked soil were revealed, and the most appropriate nitrogen source for biodegradation of semi- and non-volatile n-alkanes was investigated. Bioremediation of diesel fuel contaminated soil was monitored in lab-scale reactors for 15 days. Ammonium sulfate, potassium nitrate and urea were used as nitrogen sources. Carbon dioxide and oxygen levels in the reactors were recorded to monitor microbiological activity. Contaminant removal process was investigated by pH, heterotrophic plate count, total petroleum hydrocarbons (TPH) and C₁₀–C₂₅ n-alkane analyses. First-order kinetic constants were calculated via respirometric and contaminant concentration data. According to total C₁₀–C₂₅ n-alkane removal levels and degradation rate constants, ammonium sulfate addition resulted in the most efficient contaminant removal followed by potassium nitrate and urea. Simultaneous degradation of individual n-alkanes was observed for all of the nitrogen sources. Urea addition changed the distribution of individual n-alkane concentrations relative to the pre-experimental concentrations. Nitrogen source type had no differential effect on degradation rates of semi- (C₁₀–C₁₆) and non-volatile (C₁₇–C₂₅) fractions.     

Nitrogen Cycling and Nitric Oxide Emissions in Oil-Impacted Prairie Soils

A remote site in the Tallgrass Prairie Preserve of Oklahoma (The Nature Conservancy) was contaminated with crude oil from a pipeline break and is being bioremediated using landfarming techniques. Landfarming is designed to stimulate microbial-based catabolism of petroleum through combined dilution/mixing and fertilization-based effects. To evaluate nitrogen-based effects during remediation, the site was sectioned and treated with urea, ammonium sulfate, or ammonium nitrate. Samples were obtained from prairie soil without chemical nitrogen addition and with or without hydrocarbon contamination. Nitrogen cycling dynamics were followed by measuring ammonium, nitrite, nitrate, and volatile nitric oxide (NO_x) levels. Nitrifying and denitrifying bacterial numbers were estimated and compared to soil oxygen, carbon dioxide, and methane levels as well as to overall total petroleum hydrocarbon (TPH) reduction. For a prairie ecosystem of this type, a high level of fertilization, particularly with nitrogen, can have ecological effects almost as profound as the petroleum contamination itself. Fertilization of the oil-contaminated soil with the reduced and/or oxidized forms of nitrogen quickly resulted in elevated steady-state levels of both ammonium and nitrate, and exceptionally high levels of NO_x released from soil. Although nitrogen fertilization increased microbial nitrogen metabolism and nitrogen cycling, it had minimal effects on the overall remediation efficiency.     

Hexadecane mineralization activity in ornithogenic soil from Seabee Hook,Cape Hallett,Antarctica

Ornithogenic soils that form in penguin rookeries contain high levels of organic carbon and nitrogen. On Seabee Hook, Cape Hallett, Antartica, ornithogenic soil was contaminated with hydrocarbons following establishment of a scientific research station. In these soils hydrocarbon biodegradation could be supported by available soil nitrogen. Hexadecane mineralization activity was detected in vitro in ornithogenic soil when incubated at 5 or 15°C. At 5°C the extent of hexadecane mineralization was higher in hydrocarbon-contaminated soil than in uncontaminated soil. Alkane-degrading bacteria isolated from Seabee Hook soil were identified as Rhodococcus or Gordonia spp. or an unclassified Corynebacterineae. The alkane degraders grew on n-alkanes from heptane (C8) to eicosane (C20) and pristane, and utilized uric acid or ammonium nitrate as nitrogen source. All of the isolates possessed urease activity. Results of this study indicate biodegradation of hydrocarbons may contribute to the natural attenuation of oil spills in ornithogenic surface soils in summer.     

Bioremediation strategies for diesel and biodiesel in oxisol from southern Brazil

Leaks and spillages during the extraction, transport and storage of petroleum and its derivatives may result in environmental contamination. Biodiesel is an alternative energy source that can contribute to a reduction in environmental pollution. The aim of the present work was to evaluate biodegradation of diesel, biodiesel, and a 20% biodiesel-diesel mixture in oxisols from southern Brazil, using two bioremediation strategies: natural attenuation and bioaugmentation/biostimulation. Fuel biodegradation was monitored over 60 days by dehydrogenase activity, CO₂ evolution and gas chromatography. The bacterial inoculum employed for bioaugmentation/biostimulation consisted of Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia and PCR-DGGE using 16S RNAr primers showed that some members of this consortium survived in the soil after 60 days. The biodegradation of pure biodiesel was higher for bioaugmentation/biostimulation than for natural attenuation, suggesting that the addition of the microbial consortium, together with adjustment of the macronutrient ratio, increased biodiesel degradation. The results of dehydrogenase and respiratory activity, together with GC analysis, suggested that the presence of biodiesel may, by stimulating general microbial degradative metabolism, increase the biodegradation of petroleum diesel. The microbial community was altered by both treatments, with natural attenuation producing a lower diversity index than the amended soil. The bioaugmentation/biostimulation strategy was showed to have a high potential for cleaning up soils contaminated with diesel and biodiesel blends.     

Genotoxicity Assessment of Wood-Preserving Waste-Contaminated Soil Undergoing Bioremediation

Bioremediation represents one of the most cost-effective technologies for treatment of petroleum hydrocarbons in contaminated surface soils. A major concern for regulatory agencies when evaluating bioremediation is how to determine acceptable levels for residual organics in soil. Although guidelines have been developed for some organics in soil, limited information is available to define acceptable levels of the metabolites of biological degradation. The products of oxidative degradation are likely to be more water soluble and may also be more toxic. The purpose of the current study was to monitor changes in compound concentration and genotoxicity in soils undergoing bioremediation. The site selected for this study was a former wood-preserving site in the northwestern United States. Soil samples were collected over a 4-year period from two 6075-m² land treatment units. Conditions for biodegradation were enhanced by the addition of water and nutrients, as well as by frequent tilling to add oxygen. Due to the location of the facility, the temperature was conducive to a more rapid rate of biodegradation for approximately 6 months per year. Soil samples were collected using a grid system and solvent extracted. Polycyclic aromatic hydrocarbons were quantified in soil extracts using gas chromatography-mass spectrometry (GC/MS), and genotoxicity measured using the Salmonella/microsome assay. After 2 years of treatment, concentrations of total and carcinogenic polycyclic aromatic hydrocarbons (PAHs) were reduced to approximately 10% the concentration in the untreated soil. However, the mean weighted activity of the untreated soil was 293 net revertants per g soil, whereas the extracts of soil collected after 2 years induced a mean weighted activity of 325 net revertants per g soil. Thus, although biodegradation clearly reduced the concentration of total and carcinogenic PAHs in the surface soils, the results from the genotoxicity bioassay indicate that there was a lag in the reduction of mutagenicity in treated soils.     

Chemical Vapor Intrusion from Soil or Groundwater to Indoor Air: Significance of Unsaturated Zone Biodegradation of Aromatic Hydrocarbons

The soil vapor to indoor air exposure pathway is considered in a wide number of risk-based site management programs. In screening-level assessments of this exposure pathway, models are typically used to estimate the transport of vapors from either subsurface soils or groundwater to indoor air. Published studies indicate that the simple models used to evaluate this exposure pathway often over estimate the impact for aromatic hydrocarbons (e.g., benzene, toluene, ethylbenzene, and xy-lene or BTEX), while showing reasonable agreement for estimates of chlorinated hydrocarbon impacts (e.g., PCE, TCE, DCE). Aerobic biodegradation of the petroleum hydrocarbons is most often attributed as the source of this disparity in the model/ data comparisons. This paper looks at the significance of aerobic biodegradation of aromatic hydrocarbons as part of the assessment of chemical vapor intrusion from soil or groundwater to indoor air. A review of relevant literature summarizing the available field data as well as various modeling approaches that include biodegradation is presented. This is followed by a simple modeling analysis that demonstrates the potential importance of biodegradation in the assessment of the soil vapor to indoor air exposure pathway. The paper concludes with brief discussions of other model considerations that are often not included in simple models but may have a significant impact on the intrusion of vapors into indoor air.     

Effects of Heterogeneity and Experimental Scale on the Biodegradation of Diesel

Biodegradation of petroleum hydrocarbon contamination is a common method forremediating soils and groundwater. Due to complexities with field-scale studies,biodegradation rates are typically evaluated at the bench-scale in laboratory studies.However, important field conditions can be difficult to mimic in the laboratory. Thisstudy investigates three scaling factors that can impact laboratory biodegradation ratesand that are frequently unaccounted for in typical laboratory experimental procedures.These factors are soil heterogeneity, morphology of petroleum hydrocarbon non-aqueous phase liquids (NAPLs) and soil moisture distribution. The effects of these factors on the biodegradation rate of diesel NAPL is tested under a variety of experimental procedures from well-mixed batch studies to four-foot static soil columns. The results indicate that a high degree of variability results from even small-scale heterogeneities. In addition, it appears that as the experimental scale increases, the measured biodegradation rates slow. The results indicate that diesel biodegradation rates derived from small-scale experiments are not necessarily representative of field-scale biodegradation rates.     

Effects of diurnal temperature variation on microbial community and petroleum hydrocarbon biodegradation in contaminated soils from a sub‐Arctic site

Contaminated soils are subject to diurnal and seasonal temperature variations during on‐site ex‐situ bioremediation processes. We assessed how diurnal temperature variations similar to that in summer at the site from which petroleum hydrocarbon‐contaminated soil was collected affect the soil microbial community and the extent of biodegradation of petroleum hydrocarbons compared with constant temperature regimes. Microbial community analyses for 16S rRNA and alkB genes by pyrosequencing indicated that the microbial community for soils incubated under diurnal temperature variation from 5°C to 15°C (VART5‐15) evolved similarly to that for soils incubated at constant temperature of 15°C (CST15). In contrast, under a constant temperature of 5°C (CST5), the community evolved significantly different. The extent of biodegradation of C10–C16 hydrocarbons in the VART5‐15 systems was 48%, comparable with the 41% biodegradation in CST15 systems, but significantly higher than CST5 systems at 11%. The enrichment of Gammaproteobacteria was observed in the alkB gene‐harbouring communities in VART5‐15 and CST15 but not in CST5 systems. However, the Actinobacteria was abundant at all temperature regimes. The results suggest that changes in microbial community composition as a result of diurnal temperature variations can significantly influence petroleum hydrocarbon bioremediation performance in cold regions.     

Isolation and Characterization of a New Benzene,Toluene, and Ethylbenzene Degrading Bacterium, <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. B113

A bacterium designated strain B113, able to degrade benzene, toluene, and ethylbenzene compounds (BTE), was isolated from gasoline-contaminated sediment at a gas station in Geoje, Korea. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate belonged to the genus Acinetobacter. The biodegradation rates of benzene, toluene, and ethylbenzene were relatively low in MSB broth, but the addition of yeast extract had a substantial impact on the biodegradation of BTE compounds, which suggested that yeast extract might provide a factor that was necessary for its growth or BTE biodegradation activity. However, interestingly, the biodegradation of BTE compounds occurred very quickly in slurry systems amended with sterile soil. Moreover, if soil was combusted first to remove organic matters, the enhancement effect on BTE biodegradation was lost, indicating that some insoluble organic compounds were probably beneficial for BTE degradation in contaminated sediment. This study suggests that strain B113 may play an important role for biodegradation of BTE in the contaminated site.     

Effects of amendments on biodegradation of crude petroleum by sediment bacteria from Bonny River Estuary

The biodegradation of Bonny light crude petroleum by bacteria in batch culture was enhanced by the addition to culture media, of 0.2 mg of urea and soya bean lecithin per 100 ml of crude oil, sediment and water mixture. Biodegradation was found to be purely an aerobic process. There was a direct relationship between hydrocarbon content and proportion (%) of total heterotrophic count that was capable of growing on crude petroleum as sole carbon and energy source.     

Petroleum biodegradation in marine environments

Petroleum-based products are the major source of energy for industry and daily life. Petroleum is also the raw material for many chemical products such as plastics, paints, and cosmetics. The transport of petroleum across the world is frequent, and the amounts of petroleum stocks in developed countries are enormous. Consequently, the potential for oil spills is significant, and research on the fate of petroleum in a marine environment is important to evaluate the environmental threat of oil spills, and to develop biotechnology to cope with them. Crude oil is constituted from thousands of components which are separated into saturates, aromatics, resins and asphaltenes. Upon discharge into the sea, crude oil is subjected to weathering, the process caused by the combined effects of physical, chemical and biological modification. Saturates, especially those of smaller molecular weight, are readily biodegraded in marine environments. Aromatics with one, two or three aromatic rings are also efficiently biodegraded; however, those with four or more aromatic ring are quite resistant to biodegradation. The asphaltene and resin fractions contain higher molecular weight compounds whose chemical structures have not yet been resolved. The biodegradability of these compounds is not yet known. It is known that the concentrations of available nitrogen and phosphorus in seawater limit the growth and activities of hydrocarbon-degrading microorganisms in a marine environment. In other words, the addition of nitrogen and phosphorus fertilizers to an oil-contaminated marine environment can stimulate the biodegradation of spilled oil. This notion was confirmed in the large-scale operation for bioremediation after the oil spill from the Exxon Valdez in Alaska. Many microorganisms capable of degrading petroleum components have been isolated. However, few of them seem to be important for petroleum biodegradation in natural environments. One group of bacteria belonging to the genus Alcanivorax does become predominant in an oil-contaminated marine environment, especially when nitrogen and phosphorus fertilizers are added to stimulate the growth of endogenous microorganisms.     

Bioremediation of experimental petroleum spills on mineral soils in the Vestfold Hills,Antarctica

The effect of nutrient and water enhancement on the biodegradation of petroleum was tested in Antarctic mineral soils. Nitrogen, phosphorus and potassium were applied in solution, with or without gum xanthan or plastic covers, to sites artificially contaminated with distillate. The effectiveness of these procedures was assessed by measuring changes in total petroleum hydrocarbons; heptadecane/pristane and octadecane/phytane ratios; in concentrations of major hydrocarbon components and in microbial numbers and activity.Significantly lower hydrocarbon concentrations were recorded after one year in soils treated with fertilizer solutions, but only in the surface 3 cm. These soils also showed lowered heptadecane/pristane and octadecane/ phytane ratios and had the highest levels of microbial activity relative to other plots. Soils treated with gum xanthan. or covered with plastic had the highest residual hydrocarbon levels. Both treatments inhibited evaporative loss of hydrocarbon, and there were indications that gum xanthan was utilized by the microbiota as an alternative carbon source to distillate. Higher temperatures were recordecd under the plastic but no stimulation of biodegradation was detected.Estimated numbers of metabolically active bacteria were in the range 10⁷ to 10⁸ g^–1 dry weight of soil, with an estimated biomass of 0.03 to 0.26 mg g^–1 soil. Estimated numbers of amoebae were in the range 10⁶ to 10⁷ g^–1 soil (biomass of 2 to 4 mgg^–1). The highest populations were recorded in fertilized, contaminated soils, the only soils where petroleum degradation was demonstrated.     

Compositional changes during landfarming of weathered michigan crude oil‐contaminated soii

Laboratory landfarming experiments were conducted to study the bioremediation potential of weathered Michigan crude oil‐contaminated soils. It was found that landfarming was successful in removing up to 90% of the total petroleum hydrocarbons (TPH) in the soil within 22 weeks of treatment. Boiling point analyses of untreated and treated soils indicate a significant removal of TPH compounds independent of molecular weight or carbon number. Up to 85% of heavy petroleum hydrocarbons with carbon numbers above 44 were biode‐graded. In addition, approximately 93% of saturated and 79% of aromatic compounds of the TPH were biodegraded during the 22 week treatment period. The use of polyethylene sheeting as a landfarm cover does not appear to adversely affect biodegradation kinetics under laboratory conditions. Finally, equilibrium leachate concentrations for BTEX and regulated (in Michigan) polynuclear aromatics (PNAs) were below the respective detection limits for each compound. It can be concluded that landfarming of these weathered soils will be highly successful in removing petroleum hydrocarbons while not adversely impacting either ground‐water or surface water quality.     

Empirical Models Estimating Carbon Dioxide Accumulation in Two Petroleum Hydrocarbon–Contaminated Soils

Bioremediation is a popular method in degrading diesel fuel contaminants from soil. Bioremediation can be enhanced by estimating the effect of important environmental parameters on microbial activity. Respirometry was used to develop empirical models describing the effects of temperature, moisture, nitrogen, and phosphorus concentration on microbial activity in a diesel-contaminated soil from Wyoming. Carbon dioxide (CO₂) data were analyzed using a base equation where its coefficient values were functions of each parameter. Two physiologically different groups of microorganisms were identified from the results under different operating temperatures. The empirical correlations were combined into one model and this model was tested against a hydrocarbon-contaminated soil collected from a site in Egypt with similar history of contamination. The predicted CO₂ evolution agreed well with the actual data obtained from the Egyptian soil samples, showing a sound predicting power of the empirical model for petroleum hydrocarbon biodegradation. Overall, the empirical correlations developed from the respirometric data provide a method to describe microbial activity in diesel-contaminated soils.     

Does Bioavailability Limit Biodegradation? A Comparison of Hydrocarbon Biodegradation and Desorption Rates in Aged Soils

In order to determine whether bioavailability limits the biodegradability of petroleum hydrocarbons in aged soils, both the biodegradation and abiotic desorption rates of PAHs and n-alkanes were measured at various time points in six different aged soils undergoing slurry bioremediation treatment. Alkane biodegradation rates were always much greater than the respective desorption rates, indicating that these saturated hydrocarbons apparently do not need to be dissolved into the aqueous phase prior to metabolism by soil microorganisms. The biodegradation of PAHs was generally not mass-transfer rate limited during the initial phase, while it often became so at the end of the treatment period when biodegradation rates equaled abiotic desorption rates. However, in all cases where PAH biodegradation was not observed or PAH removal temporarily stalled, bioavailability limitations were not deemed responsible for this recalcitrance since these PAHs desorbed rapidly from the soil into the aqueous phase. Consequently, aged PAHs that are often thought to be recalcitrant due to bioavailability limitations may not be so and therefore may pose a greater risk to environmental receptors than previously thought.     

Guidelines for land‐treating petroleum hydrocarbon‐contaminated soils

During land treatment, environmental parameters are optimized to achieve the fastest and most complete biodegradation of petroleum hydrocarbons present in contaminated soils. This article provides specific guidelines for optimization of the land treatment process at a field site. In particular, the necessary steps in the land treatment procedure are outlined in the time sequence expected under field conditions. Specific steps include sampling and site assessment, determination of contaminant levels and characteristics, estimation of biodegradation potential, estimation of bacterial numbers in soil, design of the land treatment unit, adjustment of the soil pH and moisture content, addition of nutrient fertilizers and bulking agents, operation of the land treatment unit involving tilling and irrigation, periodic monitoring of specific environmental parameters, and final closure of the site. In addition, a number of examples are used to familiarize the reader with the numerical calculations involved in optimization of the land treatment operation.     

Evaluation of Soil Vapor Extraction and Bioventing for a Petroleum-Contaminated Shallow Aquifer in Korea

The feasibility of soil vapor extraction and bioventing technologies was examined for a petroleum hydrocarbon-contaminated site. The test site was highly contaminated with toluene, ethylbenzene, and xylene, due to leakage from petroleum storage tanks. Three respiration tests demonstrated that the test site conditions were appropriate for application of air-based remediation technologies. The oxygen consumption rates ranged from 4.32 to 7.68 %-O₂/day and biodegradation rates ranged from 2.72 to 4.84?mg/kg-day in respiration tests. In a 120-day soil vapor extraction pilot test, high initial mass removals (with tailing effects) were observed. As expected for the soil vapor extraction, the volatilization rate was much higher than the biodegradation rate. In a bioventing trial, the biodegradation effect was predominant, but a tailing effect was not observed. From this study, the suggested sequence of remediation is to construct an integrated system of soil vapor extraction and bioventing and initially operate the soil vapor extraction system until the volatilization rate becomes smaller than the biodegradation rate. After that, the system needs to be changed over to a bioventing mode. Field demonstration supports the feasibility of the proposed integrated system.     

Biodegradation of cyanide by Rhodococcus UKMP-5M

A new bacterial strain, Rhodococcus UKMP-5M isolated from petroleum-contaminated soils demonstrated promising potential to biodegrade cyanide to non-toxic end-products. Ammonia and formate were found as final products during growth of the isolate with KCN as the sole nitrogen source. Formamide was not detected as one of the end-products suggesting that the biodegradation of cyanide by Rhodococcus UKMP-5M may have proceeded via a hydrolytic pathway involving the bacterial enzyme cyanidase. No growth of the bacterium was observed when KCN was supplied as the sole source of carbon and nitrogen even though marginal reduction in the concentration of cyanide was recorded, indicating the toxic effect of cyanide even in cyanide-degrading microorganisms. The cyanide biodegradation ability of Rhodococcus UKMP-5M was greatly affected by the presence of organic nutrients in the medium. Medium containing glucose and yeast extract promoted the highest growth rate of the bacterium which simultaneously assisted complete biodegradation of 0.1 mM KCN within 24 hours of incubation. It was found that growth and cyanide biodegradation occurred optimally at 30°C and pH 6.3 with glucose as the preferred carbon source. Acetonitrile was used as an inducer to enhance cyanide biodegradation since the enzymes nitrile hydratase and/or nitrilase have similarity at both the amino acid and structural levels to that of cyanidase. The findings from this study should be of great interest from an environmental and health point of views since the optimum conditions discovered in the present study bear a close resemblance to the actual scenario of cyanide wastewater treatment facilities.