Microbial growth and substrate utilization kinetics

Microbial growth on and utilization of environmental contaminants as substrates have been studied by many researchers. Most times, substrate utilization results in removal of chemical contaminant, increase in microbial biomass and subsequent biodegradation of the contaminant. These are all aimed at detoxification of the environmental pollutants. Several microbial growth and biodegradation kinetic models have been developed, proposed and used in bioremediation schemes. Some of these models include Monod’s, Andrews, Bungay’s weighted model, general substrate inhibition models (GSIM) and sum kinetic models. Most research on microbial potentials to degrade chemical pollutants has been performed on a laboratory scale. There is a need to extend such studies to pilot scale as well as to fullscale field applications.Keywords: Microbial growth, substrate utilization, biodegradation, kinetics, detoxification, organic contaminants, models, environmental pollutant

Enhancement of recovery of residual oil using a biosurfactant slug

A laboratory investigation of the mobilization and displacement of residual oil in a sand-pack using biosurfactant slug was conducted. The biosurfactant employed was extracted from a culture of Pseudomonas sp. grown on kerosine- supplemented mineral salts medium. Characterization of the biosurfactant extract revealed a mixture of glycolipid and phospholipid in a ratio of 3.35:1. The irreducible water saturation (Swi) and initial residual oil saturation (Sor) of the sand-pack were 0.280 ± 0.003 and 0.373 ± 0.006, respectively. Core flooding experiment showed that an optimum oil recovery of 52.19% of the in-place residual oil was achieved at biosurfactant incubation time (BIT) of 120 h. These results suggest that biosurfactant produced by Pseudomonas species is a potential “candidate” for microbially enhanced oil recovery.Keywords: Laboratory investigation, enhanced oil recovery, biosurfactant slug, Pseudomonas specie

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: 293-29

MICROBIAL AND OTHER RELATED CHANGES IN A NIGER DELTA RIVER SEDIMENT RECEIVING INDUSTRIAL EFFLUENTS.

The microbial and other related changes of Okpoka- Woji River serving as a sink for effluents of industries located in its vicinity within the TransAmadi Industrial area were investigated. Sediment samples were collected from six sampling stations located along the channel for the assessment of total heterotrophic and hydrocarbon-utilizing bacteria, total heterotrophic and hydrocarbon-utilizing fungi, pH, electrical conductivity, redox potential, total organic carbon, oil and grease and total petroleum hydrocarbon. The mean values for the total heterotrophic and hydrocarbon- utilizing bacteria ranged from 3.4 x 105 to 7.84 x 105cfu/g and 1.58 x 105 to 4.57 x 105cfu/g respectively. The mean values of the total heterotrophic and hydrocarbon – utilizing fungal counts ranged from 1.98 x 104 to 8.83 x 104cfu/g and 5.08 x 103 to 9.93 x 103cfu/g respectively. The pH mean values ranged from 4.87 to 6.17 while the redox potential mean values ranged from 57.70 to 125.7mV. The electrical conductivity and total organic carbon mean values ranged from 138.02 to 3113µS/cm and 3.58 to 6.32% respectively. The mean values for the oil and grease and total petroleum hydrocarbon ranged from 3791.72 to 21,537.30mg/Kg and 3037.60 to 17,461.63mg/Kg respectively. The bacterial genera isolated from the samples included Nocardia, Pseudomonas. Klebsiella, Lactobacillus, Flavobacterium, Escherichia, Bacillus, Micrococcus, Proteus, Citrobacter and Staphylococcus. The fungal isolates included Rhizopus, Aspergillus, Fusarium, Mucor and Candida. The study showed that the river is being polluted by the activities of the industries operating in the area

Characterization of hydrocarbon utilizing bacteria in tropical marine sediments

Hydrocarbon utilizing bacteria present in Nembe waterside sediments, a marine habitat in Port Harcourt, Nigeria, were characterized using standard culture dependent techniques. The sediment samples were collected along the navigational route with an Eckman sediment grab (Wild Life Supply Co., NY). The samples had meant total heterotrophic bacterial count of 6.6 × 107cfu g-1 and hydrocarbon utilizing bacteria of 8.22 × 102 cfu g-1. The hydrocarbon utilizing bacteria isolated and identified belonged to the following genera; Bacillus, Nocardia, Staphylococcus, Pseudomonas, Flavobacterium, Escherichia, Acinetobacter and Enterobacter. Bacillus spp. were the most isolated followed by Pseudomonas spp. Gas chromatographic analysis of the sediment sample showed a total petroleum hydrocarbon concentration of 102.02 mg kg-1 and presence of higher chain hydrocarbons like C14, C16, C18 and C28. Species of the bacteria isolated are known hydrocarbon  degraders and it is assumed that the genera identified from the sediment may have the catabolic capability to use petroleumhydrocarbons as source of carbon. Thus the marine sediments of the Niger Delta, Nigeria may habour important genera of bacteria that may have beneficial applications in petroleum microbiology

Effect of Petroleum Fuels and Lubricants on Soil Properties of Auto-mechanic Workshops and Garages in Cape Coast Metropolis, Ghana

Soil properties of petroleum hydrocarbon contaminated soils from automobile mechanical shops in the Cape Coast Municipality of the Central Region of Ghana were investigated to assess their alternation due to the petroleum hydrocarbon contamination. Soil samples were collected from eight automobile mechanical shops and control sites and analyzed using standard protocols. The mean particle size distribution followed the order: sand 64.79±19.47 > silt 22.81±9.47 > 12.40±14.68. The distributions for the control samples followed a similar order. The particle size distribution of soils from the study sites was not significantly different from those of the control sites (p<0.05). There were greater variations in soil characteristics of control samples than those of the contaminated soils, with significant differences observed between most of the soil characteristics of the two sites (p<0.05). Significant correlations were observed between some soil properties, between temperature and conductivity (p< 0.01; r=-0.689); temperature and organic matter (p< 0.05; r= 0.422); pH and conductivity (p< 0.01; r= 0.549); pH and nitrate (p< 0.05; r= 0. 430); pH and Phosphate (p< 0.01; r= 0.652); nitrate and phosphate (r= 0. 728, p< 0.01), organic matter and phosphate (p< 0.01; r= 0. 692); moisture and nitrate (r= 0. 787, p< 0.0); and between moisture and phosphate (r= 0. .633, p< 0.01). Petroleum hydrocarbon contamination altered soil properties and may adversely affect sensitive bacteria.Keywords: Physiochemical properties, Soil, Petroleum hydrocarbon, Contaminatio

Crude Oil-Degradation and Plasmid Profile of Nitrifying Bacteria Isolated from Oil-Impacted Mangrove Sediment in the Niger Delta of Nigeria

The crude oil degradability and plasmid profile of autotrophic nitrifying bacteria, Nitrosomonas and Nitrobacter species, isolated from mangrove sediment in the Niger Delta of Nigeria were studied. The effects of temperature, pH and optical density on the utilization of different carbon sources by the bacteria were also investigated. Results showed that nitrifying bacteria could utilize kerosene, diesel oil, jet fuel and engine oil as carbon sources. None utilized hexane and xylene but moderate growth was observed in benzene, phenol and toluene. However, their ability to utilized crude oil varied both in rates of utilization and in growth profiles. Mixed culture of the isolates degrades 52 % of crude oil introduced into the medium followed by Nitrosomonas sp. with 40 % degradation. The least was Nitrobacter sp. with 20 % degradation. The ability of the autotrophs to degrade crude oil was found to be plasmid-mediated through curing experiment and electrophoresis. The size of the plasmid involved was estimated to be 23 kb. The high crude oil utilization of the mixed culture implies that nitrifying bacteria isolated from contaminated ecosystem are excellent crude oil degraders and can be harnessed for bioremediation purposes

Environmental and Microbial Influences on Corrosion of Selected Types of Petroleum Industry Steel

This study explored the influence of brackish water sediment, mangrove swamp sediment, clayey/lateritic soil, and river water (freshwater) sediment on the corrosion rates of carbon, mild, and stainless steels and the species of sulphate reducing bacteria (SRB) and iron bacteria associated with the process. The material loss following burial of the steel samples for a 9-month period was assessed. Standard and specialised microbiological techniques were employed in the characterisation of the bacterial species. Qualitative assessment for corrosion was done via optical microscopy and macroscopy. Corrosion was highest on steel buried in brackish water sediment and lowest in that from river water sediment. Carbon steel was the most susceptible to corrosion while stainless steel was the most resistant. Sulphite, sulphide, nitrate and phosphate concentrations had a strong impact on corrosion rates. Thiobacillus, Leptothrix and Gallionella dominated amongst the iron bacteria while Desulfobacter and Desulfovibrio dominated amongst the SRB. There were significant differences in corrosion rates and bacterial abundance from one environment to the other. Iron bacteria showed greater abundance than SRB across the different environments and steel types. Iron bacteria counts, however, did not correlate positively with corrosion rates. The findings suggest that oil industry facilities in brackish water environments are more liable to corrosion than those located in fresh water ecosystems