Biodegradation Studies Research Articles

Accumulation of manganese oxides in biological activated carbon filters: Implications for biodegradation studies

AbstractA comparison of granular and biological activated carbon (GAC and BAC) media used for drinking water treatment was made to assess differences in surface elemental composition. Fresh GAC, recently commissioned GAC and end‐of‐service life BAC from a water treatment plant in New Zealand were analyzed using scanning electron microscopy, energy‐dispersive spectroscopy, and inductively coupled plasma‐mass spectrometry (ICP‐MS). Imaging revealed dense microbial colonization of the BAC surface compared to GAC media, and a mineralized surface layer high in manganese and oxygen. ICP‐MS analysis also confirmed high levels of Mn in the BAC media relative to GAC media. As many bacterial species known to colonize BAC filters are also known as Mn oxidizers, this suggests a biogenic origin of the Mn‐oxide deposition on the BAC surface. Given the properties of Mn‐oxides, they may be implicated in the mechanism by which bacteria capture and metabolize substrates in BAC filters.

Sustainable polyesters via direct functionalization of lignocellulosic sugars.

The development of sustainable plastics from abundant renewable feedstocks has been limited by the complexity and efficiency of their production, as well as their lack of competitive material properties. Here we demonstrate the direct transformation of the hemicellulosic fraction of non-edible biomass into a tricyclic diester plastic precursor at 83% yield (95% from commercial xylose) during integrated plant fractionation with glyoxylic acid. Melt polycondensation of the resulting diester with a range of aliphatic diols led to amorphous polyesters (Mn = 30-60 kDa) with high glass transition temperatures (72-100 °C), tough mechanical properties (ultimate tensile strengths of 63-77 MPa, tensile moduli of 2,000-2,500 MPa and elongations at break of 50-80%) and strong gas barriers (oxygen transmission rates (100 µm) of 11-24 cc m-2 day-1 bar-1 and water vapour transmission rates (100 µm) of 25-36 g m-2 day-1) that could be processed by injection moulding, thermoforming, twin-screw extrusion and three-dimensional printing. Although standardized biodegradation studies still need to be performed, the inherently degradable nature of these materials facilitated their chemical recycling via methanolysis at 64 °C, and eventual depolymerization in room-temperature water.

Engineering Pseudomonas putida To Produce Rhamnolipid Biosurfactants for Promoting Phenanthrene Biodegradation by a Two-Species Microbial Consortium.

ABSTRACTPolycyclic aromatic hydrocarbons (PAHs) are a group of organic contaminants that pose a significant environmental hazard. Phenanthrene is one of the model compounds for the study of biodegradation of PAHs. However, the biodegradation of phenanthrene is often limited by its low water solubility and dissolution rate. To overcome this limitation, we engineered a strain of Pseudomonas putida to produce rhamnolipid biosurfactants and thereby promote phenanthrene biodegradation by an engineered strain of Escherichia coli constructed previously in our lab. The E. coli-P. putida two-species consortium exhibited a synergistic effect of these two distinct organisms in degrading phenanthrene, resulting in an increase from 61.15 to 73.86% of the degradation ratio of 100 mg/L phenanthrene within 7 days. After additional optimization of the degradation conditions, the phenanthrene degradation ratio was improved to 85.73%.IMPORTANCE Polycyclic aromatic hydrocarbons (PAHs), which are recalcitrant, carcinogenic, and tend to bioaccumulate, are widespread and persistent environmental pollutants. Based on these characteristics, the U.S. Environmental Protection Agency has listed PAHs as priority contaminants. Although there are many methods to treat PAH pollution, these methods are mostly limited by the poor water solubility of PAHs, which is especially true for the biodegradation process. Recent evidence of PAH-contaminated sites suffering from increasingly severe impact has emerged. As a result, the need to degrade PAHs is becoming urgent. The significance of our study lies in the development of nonpathogenic strains of biosurfactant-producing Pseudomonas aeruginosa for promoting the degradation of phenanthrene by engineered Escherichia coli.

INVESTIGATION OF THE ABILITY TO BIODEGRADABILITY OF POLYURETHANE FOAM COMPOSITE MATERIALS WITH ALBUCID AND THE DYNAMICS OF ALBUCID RELEASE IN VITRO

Studies of biodegradability of polyurethane foam (PUF) composite materials with albucid under the influence of biological medium 199 (BM 199) and saline solution for 2 weeks, 1, 3 and 6 months were conducted. IR spectroscopy, physical-mechanical tests, DSC and TGA before and after incubation in model mediums were investigated. It was found that the influence of BM 199 and saline solution on the structure and properties of composite materials with albucid is similar. According to the results of physical-mechanical studies under the influence of model mediums there are processes of biodegradation which are confirmed by a decrease in adhesive strength after incubation in BM 199 and saline solution. According to IR spectroscopy, biodegradation is accompanied by redistribution of hydrogen bonds of NH groups of the polymer matrix. The results of studies by the DSC method indicate a decrease of Tg and increase of ΔСР of PUF composites with albucid compared to the control, which is associated with increasing of segmental mobility of macromolecules under the influence of model mediums and due to the albucid release from polymer matrix. It was found that PUF and PUF composites with albucid in vitro remain heat-resistant materials, because after incubation in BM 199 and a saline solution there is an increase in T0 and Tmax by the TGA method. Studies of the dynamics of albucid release from the PUF matrix were carried out. It was found that the composite materials are capable to the prolonged release of the drug. The amount of released albucid is 36.0 % on the 60th day of the experiment, which does not exceed the therapeutic dose and has no toxic effects. Therefore, polyurethane foam composite materials with albucid can be proposed as promising materials for use as implants with prolonged action of albucid in ophthalmological surgery.

Exploring bacterial communities through metagenomics during bioremediation of polycyclic aromatic hydrocarbons from contaminated sediments

The goal of this study was to evaluate the degradation effectiveness of PAHs degrading bacteria at the mesocosm level, including Stenotrophomonas maltophilia (SC), mixed culture (MC), and enriched native microflora (EC) at the mesocosm level. Maximum degradation was found in the mesocosm MC (26.67 %), followed by SC (25.08 %) and EC (18.25 %) after 60 days. Thus, mixed culture and Stenotrophomonas maltophilia could be a game changer in the PAHs bioremediation at the chronically contaminated sites. MiSeq sequencing has revealed dominancy of γ-Proteobacteria, α-Proteobacteria, β-Proteobacteria at class level and Sphingomonadales, oceanospirillales, Rhodothermales at Order level. Families Alcanivoracaceae, Alteromonadaceae, Nocardiaceae, Rhodospirillaceae and genus Stenotrophomonas, Alcanivorax, Methylophaga, Fluviicola and Rhodoplanes were considerably increased which play key role in the PAHs degradation. Dominant bacterial communities have revealed resilience community to enable potential PAHs degradation process in all the mesocosms. To the best our knowledge this is the first ever attempt in PAHs biodegradation study conducted at the mesocosm level mimicking natural environmental conditions. Consequently, this study could be a benchmark against which future progress studies for the policy makers and stakeholders to design appropriate bioremediation study for the historically PAHs polluted contaminate sites.

Fabrication, characterization and toxicological evaluation of polyethylene glycol/sodium polystyrene sulfonate hydrogels for controlled delivery of Acetaminophen

Acetaminophen is a white crystalline odorless drug. It decreases the formation of prostaglandins by inhibiting the cyclooxygenase enzyme (COX-3), thus, used in the relieving of pain and fever. The recommended dose of acetaminophen is very high. Due to high dose intake, certain severe adverse effects such as hepatotoxicity and skin rashes are produced. Thus, a drug carrier system is needed to sustain the release of the acetaminophen and also enhance the patient compliance. Therefore, the current study was focused on the development of a new drug delivery system based on polyethylene glycol, sodium polystyrene sulfonate and acrylic acid, used for the controlled delivery of acetaminophen. The prepared hydrogel networks were subjected to a series of studies. An increment was seen in gel fraction, percent porosity, swelling, and drug release with the increasing concentrations of polymers and monomer while a decrease was detected in sol fraction. Similarly, biodegradation study indicated a slow degradation rate for the monomer content as compared to polymers contents. pH-sensitivity of the prepared hydrogel was investigated at three various pH values i.e., 1.2, 4.6, and 7.4 by both swelling and drug release studies. Cytotoxicity study presented no toxic effects on T84 human colon cancer cells. Furthermore, characterizations such as Fourier transform infrared spectroscopy, Scanning Electron Microscopy, Thermogravimetric Analysis, Differential Scanning Calorimetry and X-ray Diffraction studies were performed to assess their effects on the developed hydrogel. Conclusively, we can demonstrate that the developed hydrogel could be used as a potential candidate for the controlled release of acetaminophen.

In Vitro Biodegradation of a-C:H:SiOx Films on Ti-6Al-4V Alloy.

This paper focuses mainly on the in vitro study of a five-week biodegradation of a-C:H:SiOx films of different thickness, obtained by plasma-assisted chemical vapor deposition onto Ti-6Al-4V alloy substrate using its pulsed bipolar biasing. In vitro immersion of a-C:H:SiOx films in a solution of 0.9% NaCl was used. It is shown how the a-C:H:SiOx film thickness (0.5–3 µm) affects the surface morphology, adhesive strength, and Na+ and Cl− precipitation on the film surface from the NaCl solution. With increasing film thickness, the roughness indices are reducing a little. The adhesive strength of the a-C:H:SiOx films to metal substrate corresponds to quality HF1 (0.5 µm in thickness) and HF2-HF3 (1.5–3 µm in thickness) of the Rockwell hardness test (VDI 3198) that defines strong interfacial adhesion and is usually applied in practice. The morphometric analysis of the film surface shows that on a-C:H:SiOx-coated Ti-6Al-4V alloy surface, the area occupied by the grains of sodium chloride is lower than on the uncoated surface. The reduction in the ion precipitation from 0.9% NaCl onto the film surface depended on the elemental composition of the surface layer conditioned by the thickness growth of the a-C:H:SiOx film. Based on the results of energy dispersive X-ray spectroscopy, the multiple regression equations are suggested to explain the effect of the elemental composition of the a-C:H:SiOx film on the decreased Na+ and Cl− precipitation. As a result, the a-C:H:SiOx films successfully combine good adhesion strength and rare ion precipitation and thus are rather promising for medical applications on cardiovascular stents and/or friction parts of heart pumps.

A Review on Biodegradation Study of Disposable Face Masks

Coronavirus disease 2019 (COVID-19) plays a vital role in the pollution of micro-plastic. Currently, the increase in the use of polypropylene-based face masks has been an issue in waste management. This scenario will someday cause big environmental problems if the wastes are improperly managed. Thus, this review is aimed at analyzing the waste contributed by face masks and studying the factors that help fasten the degradation of face masks. These findings were analyzed according to the degradation of the polypropylene-based face mask under a few headings. The results have been presented and fallen into respective categories, and it shows that polypropylene does undergo deterioration in the landfill burial under the dumping site soil. It has been confirmed that there was heavy colonization of microbial communities from the used face masks. Thus, it is recommended that more research need to be done further to test the microbial effects of polypropylene-based face masks.

Nocardioides carbamazepini sp. nov., an ibuprofen degrader isolated from a biofilm bacterial community enriched on carbamazepine

From the metagenome of a carbamazepine amended selective enrichment culture the genome of a new to science bacterial species affiliating with the genus Nocardioides was reconstructed. From the same enrichment an aerobic actinobacterium, strain CBZ_1T, sharing 99.4% whole-genome sequence similarity with the reconstructed Nocardioides sp. bin genome was isolated. On the basis of 16S rRNA gene sequence similarity the novel isolate affiliated to the genus Nocardioides, with the closest relatives Nocardioides kongjuensis DSM19082T (98.4%), Nocardioides daeguensis JCM17460T (98.4%) and Nocardioides nitrophenolicus DSM15529T (98.2%). Using a polyphasic approach it was confirmed that the isolate CBZ_1T represents a new phyletic lineage within the genus Nocardioides.According to metagenomic, metatranscriptomic studies and metabolic analyses strain CZB_1T was abundant in both carbamazepine and ibuprofen enrichments, and harbors biodegradative genes involved in the biodegradation of pharmaceutical compounds. Biodegradation studies supported that the new species was capable of ibuprofen biodegradation. After 7 weeks of incubation, in mineral salts solution supplemented with glucose (3 g l−1) as co-substrate, 70% of ibuprofen was eliminated by strain CBZ_1T at an initial conc. of 1.5 mg l−1.The phylogenetic, phenotypic and chemotaxonomic data supported the classification of strain CBZ_1T to the genus Nocardioides, for which the name Nocardioides carbamazepini sp. nov. (CBZ_1T = NCAIM B.0.2663 = LMG 32395) is proposed.To the best of our knowledge, this is the first study that reports simultaneous genome reconstruction of a new to science bacterial species using metagenome binning and at the same time the isolation of the same novel bacterial species.

Biodegradation Study of Potato Starch-Based Bioplastic

Background: Plastics are indispensable for our society. The extensive use of petroleumbased plastic and dumping of the same in soil and water body greatly affects our environment and biodiversity. However, biodegradable plastics can reduce the volume of waste in packaging materials. Therefore, biomass-derived polymers are promising alternatives to the petroleum-based non-degradable polymer to address the environmental issues. Objective: A large number of reports on the synthesis and characterization of starch-based bioplastic are available in the literature. However, a detailed biodegradation study of the starchbased bioplastic is rarely reported. We have prepared potato starch-based bioplastic with the combination of various plasticizers (glycerol, sorbitol, and xylitol) through hydrogel formation and carried out their biodegradation study. Method: Present study investigated the biodegradation of potato starch-based bioplastic in the natural environment, in cultured bacteria, and with fungal α-amylase. Results: Starch-based plastic is completely degraded in the natural environment within two months. Bacteria culture in solid media resulted in various types of bacterial colonies. Among the various bacterial colonies, the white circular colony was the major bacteria that degrade starchbased plastic. Furthermore, we screened the starch-based plastic degrading bacteria and isolated the pure culture through the streak plate method. Conclusion: In the presence of cultured bacteria and with fungal α-amylase, starch-based plastic is completely degraded within 96 h and 48 h, respectively.

Zinc improves antibacterial, anti-inflammatory and cell motility activity of chitosan for wound healing applications

We report the successful preparation and characterization of chitosan-Zn complex (ChiZn) in the form of films, intended to enhance the biological performance of chitosan by the presence of Zn as antibacterial agent and biologically active ion. The influence of Zn chelation on morphology and structure of chitosan was assessed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and infrared spectroscopy. The biodegradability study of ChiZn showed a sustained release of Zn up to 2 mg/mL. No toxic response was observed toward stromal cell line ST-2 in indirect contact with the ChiZn films. The dissolution product of ChiZn showed improved wound closure (88% closure) compared to the positive control group (70% closure). Moreover, ChiZn exhibited antibacterial activity against S. aureus together with a slight increase (~30%) in the secretion of VEGF and moderate decrease in nitric oxide evolution. Our findings indicate that ChiZn could be used as a safe and effective wound healing agent.

Jackfruit Starch Based Blends with Polyvinylpyrrolidone: Preparation, Structural Characterization, and Biodegradable Properties

AbstractStarch is extracted from the seeds of ripen jackfruit (Artocarpus heterophyllus) cultivated in Nepal by treating with distilled water and alkali solution. The properties of extracted starch are evaluated by measuring ash content, moisture content, and amylose content. A series of starch‐based biodegradable blends with polyvinylpyrrolidone (PVP) are prepared through solution casting method and their biodegradable properties are studied. The blend is characterized by thickness measurement, water solubility test, Fourier transform infrared spectroscopy (FTIR), optical microscopy, and biodegradability test. The thickness measurement shows the linear increase in thickness of the blend with the addition of starch. The water solubility test reveals the higher solubility of PVP in water than that of the starch. FTIR spectra of PVP/thermoplastic starch (PVP/TPS) blends exhibit the existence of relevant functional groups of both starch and PVP, the peaks shifting, and the change in nature of the peaks after degradation. Optical microscopy reveals the nonuniform dispersion of starch particles in the PVP matrix and the appearance of holes and fractures in composite subjected to compost soil for degradation. The biodegradability study proves that the loading of starch to PVP accelerates the degradation process.

Effects of chemical pretreatments on material solubilization of Areca catechu L. husk: Digestion, biodegradability, and kinetic studies for biogas yield

This study aimed to understand the pretreatment-aided anaerobic digestion of lignocellulosic residues and to assess the substrate solubilization capacity of pretreatment processes. We evaluated the feasibility of biogas production using chemically pretreated Areca catechu L. (Arecanut husk, AH). AH was pretreated for 24h at two different temperatures—25 °C and 90 °C with four different chemicals viz. H2SO4 (acidic), NaOH (alkaline), H2O2 (oxidative), and ethanol in 1% H2SO4 (organosolv) under each temperature. AH solubilization assessment included analyses of parameters such as volatile solids to total solids (VS:TS) ratio, soluble chemical oxygen demand, total phenolic content, and biomass composition. Alkaline pretreatment of AH at 90 °C resulted in the maximum biogas yield of 683.89mL/gVS, which was 2.3 times more than that obtained using raw AH without pretreatment. Methane content of biogas produced using AH pretreated with 2–10% of NaOH was found to be between 71.53% and 75.06%; methane content of biogas using raw AH was 62.31%. In order to describe the AH degradation patterns, biogas production potential from pretreated AH was evaluated using bacterial kinetic growth models (First-order exponential, logistic, transference, and modified Gompertz models). The modified Gompertz and logistic models (correlation coefficient >0.99) were found to have the best fit of all kinetic models for the cumulative experimental biogas curve. We formulated a multiple linear regression equation depicting the biodegradability index (BI) as a technical tool to determine biomethane production; BI is represented as a function of biomass composition (cellulose, hemicellulose, and lignin), with a high correlation (>0.95). Based on our analyses of AH pretreatment and substrate utilization for biogas production, we propose that the biochemical composition of lignocellulosic residues should be carefully considered to ensure their biodegradability when subjected to anaerobic digestion.

A Study of Biodegradation of Hybrid Bioplastic Films Blend from Manihot and Triticum Biopolymer

Environmental concerns associated with synthetic plastics are detrimental and have made it very crucial to develop biodegradable polymers for commercial and industrial uses. This work investigates the biodegradability of starch (biopolymer) based bioplastics through the soil burial test (SBT) technique. The biopolymeric films were synthesized from 190 and 250 µm biopolymer particulates of manihot esculenta and triticum aestivum. Blends from each particle size were produced in varied proportions with other additives. The biopolymeric films were characterized by physical, physiochemical, thermal, and microstructural tests. The biodegradability of starch-based polymers was determined by a soil burial test for 30 days where topsoil was used as a source of microbial activity. The conventional polyethylene film was also applied to the test. The bioplastic films were observed to have cracks on the surface and became hard and brittle at the end of the testing period. The total weight loss of 46.55–63.77 % was achieved by the bioplastic films. The LDPE film showed no trace of macro-structural changes or any weight reduction throughout the soil burial test. This research concludes that bioplastic films outperformed ordinary plastic films, as they were proven to be biodegradable; and can be employed efficiently in packaging applications.

A biodegradable chipless sensor for wireless subsoil health monitoring

Precision Agriculture (PA) is an integral component of the contemporary agricultural revolution that focuses on enhancing food productivity in proportion to the increasing global population while minimizing resource waste. While the recent advancements in PA, such as the integration of IoT (Internet of Things) sensors, have significantly improved the surveillance of field conditions to achieve high yields, the presence of batteries and electronic chips makes them expensive and non-biodegradable. To address these limitations, for the first time, we have developed a fully Degradable Intelligent Radio Transmitting Sensor (DIRTS) that allows remote sensing of subsoil volumetric water using drone-assisted wireless monitoring. The device consists of a simple miniaturized resonating antenna encapsulated in a biodegradable polymer material such that the resonant frequency of the device is dependent on the dielectric properties of the soil surrounding the encapsulated structure. The simple structure of DIRTS enables scalable additive manufacturing processes using cost-effective, biodegradable materials to fabricate them in a miniaturized size, thereby facilitating their automated distribution in the soil. As a proof-of-concept, we present the use of DIRTS in lab and field conditions where the sensors demonstrate the capability to detect volumetric water content within the range of 3.7–23.5% with a minimum sensitivity of 9.07 MHz/%. Remote sensing of DIRTS can be achieved from an elevation of 40 cm using drones to provide comparable performance to lab measurements. A systematic biodegradation study reveals that DIRTS can provide stable readings within the expected duration of 1 year with less than 4% change in sensitivity before signs of degradation. DIRTS provides a new steppingstone toward advancing precision agriculture while minimizing the environmental footprint.

Study of Resistive Switching and Biodegradability in Ultralow Power Memory Device Based on All‐Inorganic Ag/AgBi2I7/ITO Structure

AbstractThe cross‐compatibility of electronic devices and biomedicine has greatly promoted the new medical diagnosis and treatment technology. Developing biodegradable resistive random access memory device (ReRAM) with low power is key to biomedical application. In this paper, the all‐inorganic air‐stable and high‐quality AgBi2I7 perovskite‐like film is successfully prepared by introducing Ag+ into the Bi‐I system. The device has a higher ON/OFF ratio after annealing in NH3 compared with annealing in vacuum, and the switching behavior changes from gradual type to abrupt filamentary type. Meanwhile, ultralow power characteristic with the set power of 6.9 × 10–7 W (0.42V@1.6 × 10–6A) and the reset power of 1.5 × 10–8 W (1V@1.5 × 10–8A) is achieved in the Ag/AgBi2I7/ITO memory devices after annealing in NH3. Good biodegradability is affirmed via put Ag/AgBi2I7/ITO device in PBS solution. Results show that the Ag/AgBi2I7/ITO memory devices are the promising candidate in the field of biomedical application.

Consumption of low-density polyethylene, polypropylene, and polystyrene materials by larvae of the greater wax moth, Galleria mellonella L. (Lepidoptera, Pyralidae), impacts on their ontogeny.

Low-density polyethylene (LDPE), biaxially oriented polypropylene (BOPP), and expanded polystyrene (EXPS) are the most common plastics found in every home of the world, but only ~ 10% enter the recycling chains. Consequently, the study of plastic biodegradation by microorganisms and insects, such as the wax moths, has gained special interest. Galleria mellonella (L.) has been shown to consume single-layered polyethylene and polystyrene, though biological impacts of this consumption have been rarely reported. We evaluated the consumption of different plastics by G. mellonella larvae (L7, mean size: 25-30 mm) and its effect on larval duration, survival, and development. For this, we offered the larvae five diets: single-layered LDPE, EXPS, BOPP, triple-layered polyethylene (SB, for silo-bags), and a control with beeswax. We recorded the state and weight of the materials and the state of larvae until they reached the adult stage. Larvae consumed more PE (both LDPE and SB) and EXPS than BOPP; still, they were able to emerge as adults in all treatments. Larvae that consumed plastics turned into pupal stage faster than those that consumed beeswax, regardless of the type and amount of plastic consumed. This is the first report of wild G. mellonella larvae in Argentina consuming biaxially polypropylene and silo-bags.

Anaerobic phenanthrene biodegradation by a new salt-tolerant/halophilic and nitrate-reducing Virgibacillus halodenitrificans strain PheN4 and metabolic processes exploration

The biodegradation of polycyclic aromatic hydrocarbons (PAHs) under hypersaline environments has received increasing attention, whereas the study of anaerobic PAH biodegradation under hypersaline environments is still lacking. Here, we found a pure culture designated PheN4, which was affiliated with Virgibacillus halodenitrificans and could degrade phenanthrene with nitrate as the terminal electron acceptor and a wide range of salinities (from 0.3% to 20%) under anaerobic environments. The optimal salinity for biodegradation of phenanthrene by PheN4 was 5%, which could degrade 93.5% of 0.62 ± 0.04 mM phenanthrene within 10 days with the initial inoculum of 0.01 gVSS/L. Meanwhile, an increased microbial amount could efficiently promote the phenanthrene biodegradation rate. The metabolic processes of anaerobic phenanthrene biodegradation under hypersaline conditions by PheN4 were proposed based on intermediates and genome analyses. Phenanthrene was initially activated via methylation to form 2-methylphenanthrene. Next, fumarate addition and β-oxidation or direct oxidation of the methyl group, ring reduction and ring cleavage were identified as the midstream and downstream steps. In addition, PheN4 could utilize benzene, naphthalene, and anthracene as carbon sources, but Benz[a]anthracene, pyrene, and Benzo[a]pyrene could not be biodegraded by PheN4. This study could provide some guidance for the bioremediation of PAH pollutants in anaerobic and hypersaline zones.

Biodegradation of Spent Automobile Engine Oil in Soil Microcosms Amended with Cow Dung

The discharge of spent engine oil in terrestrial and aquatic environments constitutes public health and socio-economic hazards. In this study, the potentials of organic waste (cow dung) amendments as biostimulating agents of the indigenous microflora for hydrocarbon biodegradation in soil microcosms deliberately contaminated with spent engine oil (5%v/w) was investigated for a period of 6 weeks. Physico-chemical and microbiological analysis of soil samples was determined using standard methods. A microcosm constructed consists of 8 trays containing 1kg of soil, artificially contaminated with 50ml of spent engine oil and treated with 50g, 100g and 150g of cow dung. Spent engine oil degradation was assessed gravimetrically at weekly interval and chromatographically after 6 weeks of biodegradation treatment. Results of the physico-chemical analysis showed that the pH of soil was 6.56 while nitrate, moisture content, phosphate and total organic content were 0.82mg/kg, 9.28%, 0.73mg/kg and 3.60mg/kg respectively. Microbiological analysis of the soil sample showed that the total heterotrophic bacteria were 3.6x106cfu/g, while total heterotrophic fungal and hydrocarbon utilizing bacteria (HUB) were 2.2x104cfu/g and 7.9 x104cfu/g respectively. The mean value of the total viable counts (TVC) population of hydrocarbon-utilizers was higher in biostimulated soil which ranged from (2.10x105-5.30x109cfu/g) compared with that of control (1.20x105-3.10x108cfu/g). Residual oil concentration showed a more remarkable decrease throughout the incubation period (0.400-0.259mg/g, 0.420-0.218mg/g and 0.410-0.220mg/g for treatments 1, 2 and 3 respectively) when compared to that of control which ranged from 0.400-0.304mg/g. At the end of 6 weeks of microcosms biodegradation studies, percentage degradations of the spent engine oil were 23.81%, 35.29%, 45.45% and 44.94% for CON, T1, T2 and T3 respectively. The result obtained from this study showed that cow dung can be effectively used as a biostimulant during bioremediation of spent engine oil polluted site to enhance biodegradation ability of the indigenous microbial population.

Modeling Dehalogenase PceA to Evaluate Pollutant Organohalide Biodegradation

Per‐ and polyfluoroalkyl substances (PFAS) are ubiquitous pollutants found in water and land environments. Environmental buildup of organohalides, such as perchloroethylene (PCE) and trichloroethene (TCE), used in dry cleaning, firefighting foams, and food packaging, pose an increasing public health risk due to their slow degradation. PFAS molecules are now observed in the blood of humans and animals across the world, and their full impact on health is yet to be determined. Studies of PFAS biodegradation have been reported within various microbial organisms. One reductive dehalogenase identified is PceA from Sulfurospirillium multivorans. The Summit Country Day School MSOE Center for Biomolecular Modeling MAPS team used 3D modeling and printing technology to investigate the active site of the reductive dehalogenase PceA. PceA is a homodimer with two independent active sites. Each active site contains a norpseudo‐B12, two 4Fe‐4S clusters as well as three highly conserved amino acids, Tyr246, Arg305, and Asn272. The short distances between the proximal iron‐sulfur cluster and the cobalt ion bound to the corrin ring of norpseudo‐B12 are thought to allow rapid electron transfer for catalysis. The invariant Tyr246 can donate a proton to neutralize the carbanion formed during catalysis. Deprotonated Tyr246 may be stabilized by the guanidinium side chain of Arg305. Additionally, the active sites have a hydrophobic pocket lined with bulky nonpolar amino acids Phe38, Trp56, Tyr102, Trp96, Tyr382 and Trp376. The tightly packed hydrophobic sidechains provide a gate for substrate selection. Understanding PFAS biodegradation and identifying additional reductive dehalogenases is urgent in addressing the pollution that faces our environment and critical in ensuring the health of humans and ecosystems.