Latest Research on Enhanced Biodegradation : Dec 2021


Cyclodextrin-Enhanced Biodegradation of Phenanthrene

The effectiveness of in situ bioremediation in many systems may be constrained by low contaminant bioavailability due to limited aqueous solubility or a large magnitude of sorption. The objective of this research was to evaluate the effect of hydroxypropyl-β-cyclodextrin (HPCD) on phenanthrene solubilization and biodegradation. Results showed that analytical-grade HPCD can significantly increase the apparent solubility of phenanthrene. The increase in apparent solubility had a major impact on the biodegradation rate of phenanthrene. For example, in the presence of 105 mg L-1 HPCD, the substrate utilization rate increased from 0.17 mg h-1 to 0.93 mg h-1 while the apparent solubility was increased from 1.3 mg L-1 to 161.3 mg L-1. As a result, only 0.3% of the phenanthrene remained at the end of a 48 h incubation for the highest concentration of HPCD tested (105 mg L-1). In contrast, 45.2% of the phenanthrene remained in the absence of HPCD. Technical-grade HPCD, which contains the biodegradable impurity propylene glycol, also increased the substrate utilization rate, although to a lesser extent than the analytical-grade HPCD. On the basis of these results, it appears that HPCD can significantly increase the bioavailability, and thereby enhance the biodegradation, of phenanthrene.[1]


Enhanced biodegradation of aromatic pollutants in cocultures of anaerobic and aerobic bacterial consortia

Toxic aromatic pollutants, concentrated in industrial wastes and contaminated sites, can potentially be eliminated by low cost bioremediation systems. Most commonly, the goal of these treatment systems is directed at providing optimum environmental conditions for the mineralization of the pollutants by naturally occurring microflora. Electrophilic aromatic pollutants with multiple chloro, nitro and azo groups have proven to be persistent to biodegradation by aerobic bacteria. These compounds are readily reduced by anaerobic consortia to lower chlorinated aromatics or aromatic amines but are not mineralized further. The reduction increases the susceptibility of the aromatic molecule for oxygenolytic attack. Sequencing anaerobic and aerobic biotreatment steps provide enhanced mineralization of many electrophilic aromatic pollutants. The combined activity of anaerobic and aerobic bacteria can also be obtained in a single treatment step if the bacteria are immobilized in particulate matrices (e.g. biofilm, soil aggregate, etc.). Due to the rapid uptake of oxygen by aerobes and facultative bacteria compared to the slow diffusion of oxygen, oxygen penetration into active biofilms seldom exceeds several hundred micrometers. The anaerobic microniches established inside the biofilms can be applied to the reduction of electron withdrawing functional groups in order to prepare recalcitrant aromatic compounds for further mineralization in the aerobic outer layer of the biofilm.[2]


Role of Soil pH in the Development of EnhancedBiodegradation ofFenamiphos

Repeatedtreatment with fenamiphos (ethyl 4-methylthio-m-tolylisopropylphosphoramidate) resulted in enhanced biodegradation of thisnematicide in two United Kingdom soils with a high pH (≥7.7).In contrast, degradation of fenamiphos was slow in three acidic UnitedKingdom soils (pH 4.7 to 6.7), and repeated treatments did not resultin enhanced biodegradation. Rapid degradation of fenamiphos wasobserved in two Australian soils (pH 6.7 to 6.8) in which it was nolonger biologically active against plant nematodes. Enhanced degradingcapability was readily transferred from Australian soil to UnitedKingdom soils, but only those with a high pH were able to maintain thiscapability for extended periods of time. This result was confirmed byfingerprinting bacterial communities by 16S rRNA gene profiling ofextracted DNA. Only United Kingdom soils with a high pH retainedbacterial DNA bands originating from the fenamiphos-degradingAustralian soil. A degrading consortium was enriched from theAustralian soil that utilized fenamiphos as a sole source of carbon.The 16S rRNA banding pattern (determined by denaturing gradient gelelectrophoresis) from the isolated consortium migrated to the sameposition as the bands from the Australian soil and those from theenhanced United Kingdom soils in which the Australian soil had beenadded. When the bands from the consortium and the soil were sequencedand compared they showed between 97 and 100% sequence identity,confirming that these groups of bacteria were involved in degradingfenamiphos in the soils. The sequences obtained showed similarity tothose from the genera Pseudomonas, Flavobacterium,and Caulobacter. In the Australian soils, two differentdegradative pathways operated simultaneously: fenamiphos was convertedto fenamiphos sulfoxide (FSO), which was hydrolyzed to thecorresponding phenol (FSO-OH) or was hydrolyzed directly to fenamiphosphenol. In the United Kingdom soils in which enhanced degradation hadbeen induced, fenamiphos was oxidized to FSO and then hydrolyzed toFSO-OH, but direct conversion to fenamiphos phenol did notoccur.[3]


Enhanced Biodegradation of Spent Lubricating Oil Contaminated Soil Using Poultry Litter

Enhanced biodegradation of spent lubricating oil contaminated soil using (40% w/w) poultry litter was studied for a period of 56 days. The bacterial count ranged from 1.7×106 cfu/ml – 4.0×106 cfu/ml for oil free soil (OFS), 1.7×106–9.0×105 for oil polluted soil (OPS) and 1.7×105 – 1.0×106 for Poultry Amended oil polluted soil (PAOPS) while the fungal count ranged from 1.2 x105cfu/ml to 5.0 x 105cfu/ml OFS, 4.0×10 -5.0 x105 for OPS and 1.2×105 – 5.0x 105 for PAOPS. The result revealed higher bacterial counts in poultry litter amended soil (PAOPS) compared to oil polluted soil (OPS) and oil free soil (OFS). The fungi counts were low in all treatments (OFS, OPS and PAOPS) .Ten organisms were isolated in the course of this study. The bacteria were Bacillus spp, Micrococcus spp, Pseudomonas spp, Proteus spp and Staphylococcus spp while the fungi include yeasts, Aspergillus niger, Aspergillus flavus, Mucor Spp, Penicillium spp. PAOPS had higher nitrate and phosphorus content compared to OFS and OPS. This result indicates that poultry litter could be used as biostimulating agent to enhance the biodegradation of spent lubricating oil contaminated soil.[4]


Evaluation of Crude Oil Biodegradation Potentials of Some Indigenous Soil Microorganisms

This study evaluated the crude oil degradation potentials of some indigenous soil microorganisms. The microbial isolates were among those obtained from crude oil contaminated and uncontaminated agricultural soils of Awoye, Orioke-Iwamimo, Igodan-Lisa and Oba-Ile all in Ondo State, Nigeria. The isolates were tested for crude oil degradation potentials by visual turbidity, extent of breakdown of overlaid oil and the optical density by spectrophotometry method at the wavelength of 540 nm. Brevundimonas diminuta, Bacillus subtilis, Flavobacterium species, Enterobacter species, Klebsiella pneumoniae, Pseudomonas aeruginosa, Alcaligenes faecalis, Bacillus megaterium, Klebsiella edwardsii, Bacillus aryabhattai, Aspergillus flavus, Kodamaea ohmeri, Cephalosporium species, Mucor mucedo, Paecilomyces variotii, Candida parapsilopsis and Trichoderma species were among the sixteen bacterial and seven fungal isolates tested. The findings in this study revealed varying optical densities of 0.324-0.647 for bacteria and 0.497 -0.812 for fungi at days 11 and 17 respectively thus suggesting different responses and potentials to breakdown crude oil. The highest degradative ability was shown by Klebsiella edwardsii (OD 0.647) followed by Pseudomonas aeruginosa (OD 0.575) and Klebsiella pneumoniae (OD 0.490). Paecilomyces variotii showed the highest degradative ability (OD 0.812) among the fungi. The results also suggest that these microorganisms with high degradative ability may be useful in seeding petroleum hydrocarbon polluted agricultural soils for bioremediation.[5]


Reference

[1] Wang, J.M., Marlowe, E.M., Miller-Maier, R.M. and Brusseau, M.L., 1998. Cyclodextrin-enhanced biodegradation of phenanthrene. Environmental Science & Technology, 32(13), pp.1907-1912.

[2] Field, J.A., Stams, A.J., Kato, M. and Schraa, G., 1995. Enhanced biodegradation of aromatic pollutants in cocultures of anaerobic and aerobic bacterial consortia. Antonie van Leeuwenhoek, 67(1), pp.47-77.

[3] Singh, B.K., Walker, A., Morgan, J.A.W. and Wright, D.J., 2003. Role of soil pH in the development of enhanced biodegradation of fenamiphos. Applied and Environmental Microbiology, 69(12), pp.7035-7043.

[4] Stephen, E. and Temola, O.T., 2014. Enhanced biodegradation of spent lubricating oil contaminated soil using poultry litter. Biotechnology Journal International, pp.868-876.

[5] Ikuesan, F.A., 2017. Evaluation of crude oil biodegradation potentials of some indigenous soil microorganisms. Journal of Scientific Research and Reports, pp.1-9.

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