Environmental pollution has posed a major threat to terrestrial, aquatic, and marine ecosystems, thereby affecting microflora and micro-fauna populations. This study assessed the growth attributes of maize plants on crude oil-polluted soils amended with agro-wastes. Six kilograms each of composite soil sample was weighed and transferred into one hundred and fifty labeled plastic buckets with drainage holes for soil aeration and spiked with 300mls each of crude oil, allowing for 14 days of soil acclimatization. Soil amendments such as groundnut husks, cassava peels, empty fruit bunch of oil palm, and maize cob powder were applied and allowed for 90 days. Maize seeds were sowed, while periodic data were collected and subjected to a three-way ANOVA. The result obtained revealed that maize seeds grown on agro-wastes treated and pristine control soils show early seed germination than the crude oil-polluted control soil. The plant height obtained for GnH14P + MaC14P at 10% was the highest with a mean (of 152.81cm2), and the leaf area of the maize from soil treated with GnH14P + EFBOP14P at 10% had the highest mean (756cm2), the leaf length of maize from soil treated with GnH14P + CasP14P at 3%, 6%, and 10% was the highest with mean ranging (54-97 cm2) with no significant difference in mean values obtained. The stem girth, number of leaves, and leaf width were generally improved in the bio-remediated soils. The result for the yield performance of maize shows that the days to flowering were shortened in the bio-remediated soil compared to the prolonged flowering days observed in the crude-oil polluted control. The number of seeds per cob was high in the bio-remediated soils while no seed was obtained in the crude-oil-polluted control soils. It can be concluded that the ameliorated treatment with the agro-wastes improves the performance of maize plants in crude oil-polluted soils.

Anthropogenic activities have polluted soil and aquatic ecosystems by introducing harmful heavy metals (HMs) such as cadmium, copper, mercury, lead, manganese, nickel, zinc, and others. These HMs lead to serious health conditions in humans like cancer, skin lesions, birth defects, liver and kidney damage, and mental retardation leading to other disabilities. Conventional methods of HM remediation of contaminated soil and water include physical, chemical, biological, and integrated methods. The use of physical and chemical methods, in isolation, has been reduced in practice, owing to their negative impacts, however, work on suitable integrated approaches, and the use of organisms for HM remediation has been in steady progress since past few decades. These approaches have proved to be eco-friendly, cost-effective, and show reduced negative impacts on the environment and biota. However, there is consistent increase in anthropogenic contribution to this problem, so, to keep pace with it, more recently work is in advancement on exploiting the biological system to increase the efficiency of bioremediation, using the latest technologies such as genetic engineering and nanotechnology. This paper provides an overview of the current methods deployed to address this problem, developments made in this field in past few decades, and evokes a research thrust that might lead to novel remediation approaches in the future.

Heavy metal contamination poses grave risks to all kinds of life. The fastest growing automotive, electroplating, and battery industries release the most common heavy metal, Nickel, into the environment, which has lethal impacts on human health. Our research aims to find Ni-resistant bacteria in the metal-contaminated soil that have a great potential for removing Ni from the environment. Attempts have been made to extract and characterize Ni-resistant bacteria from automobile and electroplating industry waste-contaminated soil using serial dilution, streak plating, and various morphological, biochemical, and genetic techniques. The maximum tolerable concentration of Ni and other heavy elements, such as cadmium, lead, and aluminium for the selected isolate, was investigated using the UV-Vis spectrophotometric method. Additionally, the bacterial strain's ability to remove Ni was assessed using an atomic absorption spectrophotometer.  The current research reveals a novel strain of Kluyvera cryocrescens that could withstand Ni, Cd, Pb, Al, and combinations of these heavy metals. The maximum tolerance concentration of K. cryocrescens M7 for Ni, Cd, Pb, and Al was found to be 150 ppm, 200 ppm, 1000 ppm, and 150 ppm, respectively. Additionally, it was also observed that the bacterial strain could remove Ni by 29.57%, 35.36%, 48.41%, 46.91%, and 44.88% after 12, 24, 48, 72, and 96 hours, respectively. The strain has also exhibited resistance to vancomycin, ampicillin, carbenicillin, and streptomycin. This research discovered a novel bacterial strain, K. cryocrescens M7 that may be beneficial for removing heavy metals, particularly Ni, from metal-contaminated soil.

Textile effluents are highly colored for synthetic dyes, cause significant water pollution due to high pH, TDS, EC, BOD, and COD content, and are harmful to aquatic species. Among different treatment processes, biological treatment process is considered as a promising approach. In this investigation, a mixed aerobic bacterial consortium was used for the treatment of wastewater. In addition, the fenton process with a normal sand filter was used for treatment and compared with the biological method. The mean values of BOD, COD, TDS, EC, DO, and pH in the raw wastewater indicated that the effluent was highly contaminated according to Bangladesh standard (ECR, 1997). Both the biological treatment process and fenton process separately showed promising removal of pollution load. The aerobic mixed bacterial consortium reduced TDS (66.67%), EC (60%), BOD (91.67%), and COD (85.45%) and fenton process reduced TDS (74.71%), EC (55.11%), BOD (88.33%), and COD (83.63%) compared to the raw effluent bacterial consortium simultaneously degraded dyes and decolorized the wastewater from dark deep green to transparent. Color removal for the mixed aerobic bacterial process after 72 hours of aeration was 58.57% and for the fenton process with a normal sand filter was 80%. BOD and COD removal percentages for aerobic mixed bacterial consortium showed higher removal efficiency than the fenton process with a normal sand filter. Though 92 hours of aeration showed the maximum satisfactory result, aeration time could be reduced to 72 hours which also satisfied the Bangladeshi standard (ECR, 1997).

Butachlor (BUT) is a chloroacetanilide herbicide widely applied to rice paddies to control annual grass and broad-leaf weeds. A BUT-degrading bacterial strain (PK) was isolated from paddy soils. Biochemical and 16S rRNA sequencing characteristics confirmed the strain as Pseudomonas aeruginosa (99% resemblance). The isolate dissipated BUT (100 μg/mL) in an M9 liquid medium with a rate of 0.5 ± 0.03 day-1 and DT50 and DT90 of 1.38 ± 0.10 days and 4.58 ± 0.32 days, respectively. Soil dissipation of BUT was investigated under flooded conditions. In sterile soils, the isolate increased the dissipation of BUT (200 μg/g) (DT50 = 12.38 ± 1.83 days, DT90 = 41.12 ± 6.09 days, k = 0.06 ± 0.01 day-1) compared to sterile non-inoculated samples (DT50 = 26.87 ± 2.82 days, DT90 = 89.25 ± 9.36 days, k = 0.03 ± 0.00 day-1). In non-inoculated non-sterile soil experiments, the dissipation of BUT was faster (DT50 = 15.17 ± 2.11 days, DT90 = 50.38 ± 7.02 days, k = 0.05 ± 0.00 day-1) compared to non-inoculated sterile ones, and inoculating the isolate accelerated the removal of BUT in non-sterile soils significantly (DT50 = 8.03 ± 1.20 days, DT90 = 26.68 ± 3.97 days, k = 0.09 ± 0.01 day-1). BUT inhibited soil respiration (SR) initially for 5 days, followed by an increase until day 20. The increase in SR was more pronounced in the co-presence of BUT and the isolate. The results of this research suggest P. aeruginosa PK as a suitable candidate for BUT bioremediation.

In recent years, environmental pollution by coal mining is a long-established human activity affecting all levels of life with various environmental impacts by generating heavy metals. The presence of heavy metals even in trace amount is toxic and detrimental to all living organisms. The coal mine area in Bokaro is one of the “Toxic Hotspot” in India. Bacteria have evolved uptake and efflux mechanisms to adapt in heavy metals contaminated environments and thus represent a potential source for bioremediation processes. In the present study, we isolated and characterized eight heavy metal resistant bacteria (NK-1 to 8) from soil sample in Bokaro coal mines, India. Isolates were selected based on high level of heavy metal resistance and its biochemical characterization. The following bacteria were identified based on 16S rRNA gene sequencing Enterobacter ludwigii (KM029957; NK-1), Klebsiella pneumonia (KM029958; NK-2), Enterobacter ludwigii (KM029959; NK-3), Enterobacter ludwigii (KM029960; NK-4), Klebsiella oxytoca (KM029961; NK-5), Enterobacter cloacae (KM029962; NK-6), Acinetobacter gyllenbergii (KM029963; NK-7), Enterobacter cloacae (KM029964; NK-8). A high degree of metal resistance associated with multiple antibiotic resistances was also detected in the selected isolate which was confirmed by the presence of plasmid. These isolates can further be used for bioremediation of heavy metals from contaminated site.

Fungi are successful microorganisms in the bioremediation of environmental pollution. So, this study aimed to determine the potential of Trichoderma tomentosum to remediate cadmium, lead, and nickel contaminations from potato dextrose agar (PDA) and potato dextrose broth (PDB) media. Growth rates, toxicity tolerance sporulation, bio-sorption capacity, and bio-sorption efficiency of the fungus were evaluated under different concentrations of CdCl2, Pb(NO3)2, and NiCl2. The findings demonstrated that the growth rate of the fungus differed depending on concentration, metal type, and medium. More metals in PDA medium induced more inhibition on fungus growth rates; however, the rate was independent from the heavy metals concentrations in PDB medium. Cadmium was the most toxic metal tested against T. tomentosum, with a 72h LC50 of 37 ppm. It was about 3.16 and 4.24 times as toxic as nickel and lead, respectively. In the control condition, sporulation of the fungus began at 72 hours, but under the heavy metals, it began at 168, 168, and 192 hours, respectively, for Pb, Ni, and Cd. Both the bio-sorption capacity and efficacy of the fungus were significantly enhanced by an increase in metal content and the highest values were obtained at 200 ppm of the salts. The heavy metals total bio-sorption capacity order was Ni < Cd < Pb in the aqueous medium. The conclusion was that T. tomentosum has a greater potential for the biosorption of heavy metals; hence, the fungus may be employed for the bioremediation of heavy metals from polluted sites, particularly wastewater and industrial influents.

Bioremediation has become a trending and developing field in environmental restoration through the use of micro-organisms to utilize and reduced the concentration and toxicity of various chemical pollutants. This study is on bioremediation of hydrocarbon-polluted soils using some agricultural wastes. Ninety (90) plastic buckets were filled with 4kg each of the composite soil. The soil contained in the plastic buckets was spiked with 250ml crude oil, except in the unpolluted plastic buckets (0%) crude oil. The agro-wastes (plantain stem sap, bush mango peels, and fruited pumpkin husk powder) in single and combined forms were applied after 14 days soil pollution. The amendments were applied as follows: Pristine control (0% agro-wastes), crude-oil control (0% agro-wastes), 150g, 250g, and 350g of the agro-wastes. Soil samples were collected at 90 days for soil microbial counts and the total hydrocarbon content of the soil. Data collected were subjected to 2-way ANOVA. The result showed that the microbial population in the crude-oil polluted soil amended with different agricultural wastes significantly increased (p<0.05) the total heterotrophic and crude oil utilizing bacterial and fungal counts in the soils and the increase in microbial population result in a significant reduction in total hydrocarbon content (THC) of the soils. The reduction in the THC of the soil was treatment dependent. It is, therefore concluded that based on the efficiency of these agro-wastes in enhancing microbial degradation, further studies should be carried out on the enzyme activities and production of bio-surfactant from the wastes to shorten the degradation time.

In this study, among the 21 diesel-degrading bacteria that were isolated from an oil-polluted area in Fars (Iran), 6 bacterial strains were tested for their capability to metabolize and grow on diesel oil by degrading its hydrocarbons content. The biochemical characteristics and 16S rRNA sequence analysis of diesel-degrading bacteria showed that these strains were related to the genus Pseudomonas. Among the six isolates, five strains (L1, I2, D1, D2, and G1) were clustered with Pseudomonas aeruginosa, whereas only one strain (K3) was clustered with Pseudomonas fragi. Gas chromatographic (GC) analysis of the diesel oil that was remaining in the culture medium after 10 days of culture at 30°C showed that P. aeruginosa I2 presented the highest growth rate and diesel-oil degradation (88%) between all isolates. P. aeruginosa I2 also presented the best emulsification activity, but the best hydrophobicity was seen in P. aeruginosa G1. By applying these bacteria in bioremediation processes, diesel oil contamination in soil can be counteracted.

Greenhouse experiment was conducted for four months using Leucaena leucocephala and Pleurotus tuber-regium to determine their bioremediation potentials. Leucaena leucocephala, Pleurotus tuber-regium and Leucaena leucocephala combined with Pleurotus tuber-regium were tested for their ability to improve nutrient (N, P, K, total organic carbon) and reduce heavy metals (Zn, Ni, Pb, Cu) of soil polluted with spent engine oil [5% (w/v)] and soil without spent engine oil was used as control. Bioaccumulation of nutrients and heavy metals in Leucaena leucocephala and Pleurotus tuber-regium were also determined. The highest reduction in Zn, Ni, Pb and Cu (41%, 48.39%, 61.60 and 52.72% respectively) were recorded in soil remediated with Leucaena leucocephala alone, reduction of 30.40%, 26.53%, 48.07% and 39.60% respectively were recorded in soil remediated with Pleurotus tuber-regium alone while in soil remediated with combined Pleurotus tuber-regium and Leucaena leucocephala, reductions of 32.7%, 33.43%, 88.41% and 46.22% respectively were recorded. Bioaccumulation of Zn, Ni, Pb and Cu in Leucaena leucocephala increased by 73.41%, 85.46%, 3366.04% and 125.53% respectively, similarly in Pleurotus tuber-regium by 30.16%, 21.67%, 71.11% and 53.21% respectively. These studies have shown that Pleurotus tuber-regium and Leucaena leucocephala are capable of bioremediating spent engine oil polluted soil although, treatment with Leucaena leucocephala alone tends to be most effective of these treatments.