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Aim:The aim of this study was to evaluate the toxicological effects of plastic composted soil on some nitrifying bacteria which are Nitrosomonas sp. and Nitrobacter sp. Methodology: Five plastic composted soil samples were collected from different locations within the Edo State Waste Management site located at Iyowa in Benin City which were merged to form a composite sample. Nitrosomonas sp. and Nitrobacter sp. were isolated from the soil samples. Plastic composted soil concentrations were prepared for LC 50 and EC 50 determination. Nitrobacter and Nitrosomonas acute toxicity test was carried out. Initial nitrite concentrations were determined and plates of Winograsky agar were immediately inoculated by spread plate techniques. Nitrite accumulation and utilization were also determined and inoculation by spread plate method was carried out from the various plastic composted soil concentrations after 1 h, 2 h, 3 h and 4 h time Original Research Article intervals. Plates were incubated at room temperature (28+/-2°C) for 24 h. The percentage inhibition of bacteria (Nitrosomonas sp. and Nitrobacter sp.) was determined using the probit regression analysis in Excel Microsoft.

The study examined the effect of plastic waste on soil bacteria and fungi. The test soil samples were collected from Lokoja international market waste dump site and the control soil sample was collected from non plastic contaminated garden in Salem University, Lokoja. The samples were analysed using Gas chromatography with mass spectrometer. The test soil sample soil sample had high quantity of plastic contaminant which were Methylene chloride 17.45mg/kg, hexane 10.05mg/kg, chloroform 1.56mg/kg, toluene 5.87mg/kg, tetrachloroethylene 1.48mg/kg as compared to the control garden soil sample, which had methylene chloride 0.54mg/kg, hexane 0.26mg/kg, chloroform 0.31mg/kg, toluene 5.87mg/kg and tetrachloroethylene 0.01mg/kg. The result showed the presence of plastic in the soil and it effect on bacteria and fungi. The totals of 11 bacteria were isolated from both soil samples using nutrient agar. The bacteria isolated are; Corynebacterium spp. (12%), Enterobacter spp. (8%), Acinetobacter spp. (6%), Escherichia coli (16%), Epidermis, Bacillus subtilis (15%), Serratia sp. (8%), Proteus spp. (4%), Micrococcus luteus (7%), Flavobacterium spp. (10%), Pseudomonas aeruginosa (15%). Micrococcus luteus, Flavobacterium spp. and Pseudomonas aeruginose were not isolated in plastic composted soil sample due to the presence of plasticizers. The total of 6 fungi were isolated, namely Penicilliun expansion (12%), Sacchromyces sp. (24%), Aspergillus niger (19%), Fusarium spp. (20%), Rhizopus stolonifer (10%) and Mucor piriformis (15%). This study reveals the effect of plastic waste, as it inhibits the growth of microorganism that is important for soil activities, thereby reducing the soil nutrients, fertility and productivity.

The production of biosurfactants by Actinomycetes isolated from hydrocarbon contaminated soils and Ikpoba river sediments were evaluated. Soil samples were collected from mechanic workshops located in various parts of Benin City and Ikpoba river sediments. Physico-chemical analyses were performed. Isolation of Actnomycetes was done using starch casein agar incorporation with antibiotics incubated for 7 -10 days at 30 o C. Growth on mineral salt medium initiated the production of biosurfactants which was extracted by centrifugation and filtration followed by liquid extraction using chloroform: methanol (2:1v/v). Characterization and stability studies were conducted. The pH of the contaminated soil was 4.92 +/-0.049 while that of Ikpoba river sediments was 6.62+/-0.056. The hydrocarbon contaminated soils had a higher concentration of surphur, nitrogen, potassium, sodium, magnesium and manganese compared to Ikpoba River, but only chlorine concentration was higher in Ikpoba River. Aerobic Gram positive rods with extensive branching were observed confirming growth of Streptomyces sp. The result showed stability across different temperature ranges with no significant difference observed in the two sites in emulsification activity (P>0.05). There was significant difference observed in the mean surface tension of the biosurfactants produced from the two sites across different temperature ranges with hydrocarbon contaminated soil having higher values (P>0.05). There was also significant surface tension difference between pH2 and pH8 (P<0.05) suggesting higher activity within those ranges. The result also show stability across different salt concentrations and had foaming characteristics. Actinomycetes have complex enzymatic mechanism that aids hydrocarbon mineralization and thus increases the potential for biosurfactant production. These biosurfactants are stable across temperature ranges and are not majorly affected by salt concentration; this property aids its potential usage in decontamination of oil contaminated areas in the Niger Delta region of Nigeria and other countries.