The selection of bioremediation techniques is important for purification of contaminated soil for agricultural use. Studies on soil contaminated with petroleum substances have indicated that the applied method of remediation has a bigger impact on the development of oat seedlings than the level of contamination. A yeast inoculum appeared to be a technique which was the friendliest to vegetation of oat
Bioremediation is based on microorganisms able to use pollutants either as a source of carbon or in co-metabolism, and is a promising strategy in cleaning the environment. Using soil contaminated with petroleum products from an industrial area in Saudi Arabia (Jubail), and after enrichment with the polycyclic aromatic hydrocarbon (PAH) naphthalene, a Methylobacterium radiotolerans strain (N7A0) was isolated that can grow in the presence of naphthalene as the sole source of carbon. M. radiotolerans is known to be resistant to gamma radiation, and this is the first documented report of a strain of this bacterium using a PAH as the sole source of carbon. The commonly reported Pseudomonas aeruginosa (strain N7B1) that biodegrades naphthalene was also identified, and gas chromatography analyses have shown that the biodegradation of naphthalene by M. radiotolerans and P. aeruginosa did follow both the salicylate and phthalate pathways.
This study is aimed at measuring the effect of pig, cow, horse and poultry manures on the degradation of selected Polycyclic Aromatics Hydrocarbons present in oil sludge. Four kilograms of soil amended with 1.2 kg of oil sludge was mixed with wood chips in a ratio of 1:2 (w:v) soil mixture: wood chips. The mixture was divided into fi ve parts and four parts were separately mixed with pig, cow, horse or poultry manures in a ratio of 2:1 (w:w) and the fi fth portion was used as the control with no manure added. All experiments were incubated for 10 months at room temperature. Compost piles were turned weekly for aeration and moisture level was maintained by adding deionised water enough to prevent the compost from getting dry. Moisture level, pH, temperature, CO2 evolution and oxygen consumption were measured monthly and the ash content of the compost at the end of experimentation. Highest temperature reached was 27.5°C in all compost heaps, pH ranged from 5.5 to 7.8 and CO2 evolution was highest in poultry manure at 18.78 μg/dwt/day. Microbial growth and activities were enhanced as indicated by increase in temperature, moisture level, pH value and respiration rate in all the compost piles. Bacteria capable of utilizing PAHs were isolated, purifi ed and characterized by molecular techniques using polymerase chain reaction with specifi c universal primers and the amplicons were sequenced. Bacteria identifi ed were Bacillus, Arthrobacter and Staphylococcus species. Percentage reduction in PAHs was measured using automated soxhlet extractor with Dichloromethane and gas chromatography/mass spectrometry. Results from PAH concentration measurements showed reduction of between 77% and 99%. Co- -composting of contaminated soil with animal manures enhanced the reduction in PAHs.
Compounds present in oil sludge such as polycyclic aromatic hydrocarbons (PAHs) are known to be cytotoxic, mutagenic and potentially carcinogenic. Microorganisms including bacteria and fungi have been reported to degrade oil sludge components to innocuous compounds such as carbon dioxide, water and salts. In the present study, we isolated different bacteria with PAH-degrading capabilities from compost prepared from oil sludge and animal manures. These bacteria were isolated on a mineral base medium and mineral salt agar plates. A total of 31 morphologically distinct isolates were carefully selected from 5 different compost treatments for identification using polymerase chain reaction (PCR) of the 16S rRNA gene with specific primers (universal forward 16S-P1 PCR and reverse 16S-P2 PCR). The amplicons were sequenced and sequences were compared with the known nucleotides from the GenBank. The phylogenetic analyses of the isolates showed that they belong to 3 different clades; Firmicutes, Proteobacteria and Actinobacteria. These bacteria identified were closely related to the genera Bacillus, Arthrobacter, Staphylococcus, Brevibacterium, Variovorax, Paenibacillus, Ralstonia and Geobacillus. The results showed that Bacillus species were predominant in all composts. Based on the results of the degradation of the PAHs in the composts and results of previous studies on bacterial degradation of hydrocarbons in oil, the characteristics of these bacterial isolates suggests that they may be responsible for the breakdown of PAHs of different molecular weights in the composts. Thus, they may be potentially useful for bioremediation of oil sludge during compost bioremediation.
Three chromium resistant bacterial strains, Pseudomonas fluorescens PF28, Enterobacter amnigenus EA31 and Enterococcus gallinarum S34 isolated from tannery waste contaminated soil were used in this study. All strains could resist a high concentration of K2Cr2O7 that is up to 300 mg/L. The effect of these strains on clover plants (Trifolium campestre) in the presence of two chromium salts CrCl3 and K2Cr2O7 was studied in soil microcosm. Application of chromium salts adversely affected seed germination, root and shoot length. Bacterial inoculation improved the growth parameters under chromate stress when compared with non inoculated respective controls. There was observed more than 50% reduction of Cr(VI) in inoculated soil microcosms, as compared to the uninoculated soil under the same conditions. The results obtained in this study are significant for the bioremediation of chromate pollution.
Petroleum products are complex mixture of compounds of varied biological properties. They can cause harmful changes in contaminated ecosystems and threaten humans and living organisms as well. Bioremediation (including bioremediation stimulated by biogenic substances and inoculation with biopreparations from autochthonous bacteria and fungi) can result in creation of metabolites of a varied structure and biological activeness, which has been partly recognised. Some of them are more toxic than an initial substrate. Besides, they might have mutagenic features and be responsible for cancer. Estimation of bioremediation effectiveness in waste pits was completed with toxicological monitoring. It was led with the use of living organisms as biomarkers representing all trophic levels of a chosen ecosystem: producers, consumers and reducers. This process enables total estimation of natural environment conditions. The aim of the research was to determine the influence of petroleum contaminants and indirect metabolites (produced during bioremediation) on soil biocenose. The results of biotests (toxicity, phytotoxicity and genotoxity) have been taken into account. The following biotests, prepared and produced by Microbiotest, have been applied: PhytotoxkitTM, Ostracodtoxkit FTM, acute toxicity tests Microtox® Solid Phase and Ames mutagenicity tests. The obtained results enabled observation of changes in toxic properties during purification of the soil taken from waste pits. In addition, it can be claimed whether the areas are suitable for forest usage.