Salt Medium Research Articles

Using L-cysteine to enhance calibration range and prevent a memory effect in mercury analysis of complex samples via ICP-OES

BackgroundMercury (Hg) is a persistent pollutant occurring in the environment able to transition between different species. It can therefore be found in air, soil and water reservoirs becoming a present concern for the general population but also sensitive populations like pregnant women. Therefore, investigating organ-specific transfer mechanisms of Hg is mandatory for Hg toxicity testing. For this, an in vitro system using microporous inserts to monitor the transfer across an in vitro placental barrier has been used. However, due to the cytotoxicity of Hg only low concentrations (1.26 ×10−4 – 1.36 ×10−2 µg/µL Hg) can be applied, making Hg determination in cell culture medium using inductively coupled plasma-optical emission spectrometry challenging, especially when these trace amounts should be determined alongside other trace elements which are naturally occurring in cells and cell culture medium like the essential metals manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn). Additionally, Hg analysis on an ICP system holds also a number of challenges like a persistent memory effect and instability of Hg standard solutions. MethodsThe development of a rapid and sensitive ICP-OES method to determine Hg in different matrices like cell culture medium and cells has been performed on an Avio 220 Max ICP-OES (Perkin-Elmer) equipped with a cyclonic spray chamber and MicroMist® nebulizer. Cell lysates and cell culture medium were diluted in a mixture of 0.2 % L-cysteine, 2 % HNO3 and 0.1 % HCl and directly introduced into the ICP-OES system. Further method development included the suitability of the analysis of multiple elements like Mn, Fe, Cu, and Zn as well as the determination of the limit of detection and limit of quantification. ResultsThe combination of 0.2 % L-cysteine, 2 % HNO3 and 0.1 % HCl is able to bind and stabilize Hg ions in standard solutions and in biological matrices over a wide dynamic concentration range (1 – 500 µg/L) also alongside other metals like Mn, Fe, Cu and Zn without losses of sensitivity. A short run time of 3 min enables high throughput analysis. Additionally, the high salt and carbon concentrations in the culture medium do not affect Hg sensitivity using the ICP-OES. ConclusionThis method is a useful tool for the quantification of Hg in a variety of complex matrices including cells and cell culture media (high salt and carbon-rich (∼1 % each)) with high sensitivity and minimal sample preparation allowing high throughput. Furthermore, not only Hg can be determined in biological matrices, but even multiple elemental analysis can be carried out to address the effect of Hg on other metals homeostasis.

Direct Tungsten Extraction from Scheelite in a Molten Salt Media

Direct Tungsten Extraction from Scheelite in a Molten Salt Media

Peptidoglycan modulation by Francisella tularensis

HAYDEN HESS, STUART CANTLAY, JOSEPH HORZEMPA, Department of Biomedical Sciences, West Liberty University, West Liberty, WV 26074 and MELANIE SAL, Department of Biology, West Virginia Wesleyan College, Buckhannon, WV 26201. Peptidoglycan modulation by Francisella tularensis. Peptidoglycan, a crucial component of bacterial cell walls, plays a fundamental role in maintaining cell shape, integrity, and resistance to osmotic pressure. Mycoplasmas are the only bacteria that do not produce peptidoglycan cell walls. Other peptidoglycan-producing bacteria are capable of transiently existing without a peptidoglycan as an “L-form”, but only on solid media. Preliminary observations made by our laboratory suggested that Francisella tularensis bacteria do not produce detectible levels of peptidoglycan while growing in liquid media. However, increasing salt concentration induces the production of peptidoglycan in all bacteria. In this study we confirmed and extended these observations by incubating bacteria with fluorescent D-alanine (which integrates into the peptidoglycan during synthesis). Fluorescence microscopy revealed that very few F. tularensis bacteria produce detectable peptidoglycan in low salt media, while seemingly all individual bacteria produce this layer in high salt media. Interestingly, the genome of F. tularensis encodes two distinct beta-lactamases. Here we show that both the wild-type F. tularensis LVS and beta-lactamase null mutant were both resistant to high levels of beta-lactam antibiotics in low salt liquid media. However, only the wild type and complemented mutant strains were resistant to beta-lactam antibiotics in high salt media while the beta lactamase null mutant was susceptible. These data further support the conclusion that F. tularensis does not produce, nor need, peptidoglycan in low salt liquid media. Future studies will investigate whether peptidoglycan modulation is required to avoid detection by the innate immune system.

Development of halotolerant multi-pesticides degraders for wastewater treatment

The biotreatment performance of high saline wastewater containing multiple pesticides is significantly reduced because the growth and metabolism of activated sludge microbial communities are severely impaired by high osmotic pressure and joint toxicity of multiple pesticides. In this study, Halomonas cupida J9 was metabolically engineered by chromosomal integration of three different pesticide hydrolase genes, to create a halotolerant multi-pesticides degrader. In batch degradation experiments, the finally constructed strain J9U-PVG was able to simultaneously degrade chlorpyrifos (organophosphate), carbaryl (carbamate) and α-cypermethrin (pyrethroid) in mineral salt medium supplemented with 4 g/L glucose and 60 g/L NaCl. Total cell lysate of J9U-PVG showed obvious degradation activity against chlorpyrifos, carbaryl and α-cypermethrin. Moreover, introduced Vitreoscilla hemoglobin (VHb) can enhance oxygen-sequestering capability of J9U-PVG and introduced green fluorescent protein (GFP) can be used as a biomarker to track the activity and movement of J9U-PVG in natural environments. More importantly, J9U-PVG could simultaneously and completely degrade chlorpyrifos, carbaryl and α-cypermethrin in high saline river water. Here, we demonstrate for the first time the successful construction of a halotolerant multi-pesticides degrader. This study underscores the value of H. cupida J9 as a promising chassis for the development of a halotolerant pesticide bioremediation platform. In the future, synthetic biology may serve as a powerful tool for expanding the catalytic repertoire of extremophiles for bioremediation of extreme environments.

Brilliant green decolorization by dye decolorizing peroxidase producing bacterium, Achromobacter insolitus isolated from Forest soils of Similipal Biosphere Reserve, Odisha

Dye-decolorizing peroxidases (DyPs) are recently identified superfamily of heme-containing peroxidases which has received much attention for its potential application in dye decolourization. In the current research, six bacterial colonies (SDB1-6) showing lignolytic activity were isolated from forest soils of SBR using a minimal salt medium supplemented with alkali lignin and screened for DyP activity using brilliant green dye supplemented luria bertani agar medium. The highest DyP activity showing bacterium was identified using biochemical and 16SrRNA sequencing and was identified as Achromobacter insolitus. A. insolitus was found to be an efficient strain showing the highest DyP activity of 2.7 U/mL/ml at un-optimized condition. The RSM optimization was conducted to increase the DyP enzyme activity. A. insolitus demonstrated DyP activity of 6.20 U/mL/min with an increase of 2.29 times of enzyme activity in optimal condition of pH 7.0, temperature 25 °C, H2O2 concentration 0.1 mM, and time 24 h. The bacterium was further screened for dye decolorization taking crystal violet, methyl orange, methylene blue, brilliant green and methyl red dyes supplemented in LB medium. The bacterium showed maximum brilliant green degradation ability was analyzed using UV-Vis and FTIR analyses to characterize the degraded product. The highest brilliant green degradation activity of the A. insolitus in the present study could be exploited for bioremediation of brilliant green contaminated industrial effluents in a ecofriendly and cost effective way.

Chemical and electrochemical reduction of solid oxide fuel

In the present study, the reduction of solid UO2 was performed by chemical and electrochemical reductions in molten calcium salts. All the experiments were conducted at 1123 K. The chemical reduction was performed in molten CaCl2CaF2 by adding calcium metal, while the electrochemical reduction was performed in molten CaCl2CaF2CaO by applying a current from UO2 cathode to graphite anode. By optimizing the experimental conditions, both mechanisms were able to completely reduce the solid UO2 pellet in molten calcium salts. Post-test analyses showed neither uranium in the salt medium nor the intermediate compound on the product (uranium metal) surface.

Enhanced CO2 capture and reverse water gas shift reaction using CaO in NaCl-CaCl2 molten salt medium

This study introduces an Integrated Carbon Capture and Utilisation-Reverse Water Gas Shift (ICCU-RWGS) approach, a novel method for in situ CO2 adsorption and conversion, leveraging the synergistic effects of CaO within a NaCl-CaCl2 molten salt blend to enhance CO2 capture and conversion efficiency. Building upon this foundation, we optimize CaO concentration and operating temperature to maximize CO2 uptake and conversion performance. The research focuses on integrating CaO with a NaCl-CaCl2 molten salt blend (mass ratio 4:6) to improve CO2 sorption and conversion performance. Findings show significant enhancements in CO2 uptake and CO yield with the presence of molten salt compared to systems without it. The optimal operating temperature and CaO concentration are identified for maximum CO yield. Characterisation techniques like in-situ infrared spectroscopy, XRD, and SEM provide insights into the behavior of CaO in the molten salt, revealing the solubility of the partial carbonate formed from CO2 and CaO, dispersion of CaO particles, and their morphological characteristics. Overall, the study demonstrates the potential of CaO-molten salt integration in improving ICCU-RWGS process efficiency and contributes to the development of more effective and sustainable ICCU technologies.

The comparative plastisphere microbial community profile at Kung Wiman beach unveils potential plastic-specific degrading microorganisms.

Plastic waste is a global environmental issue that impacts the well-being of humans, animals, plants, and microorganisms. Microplastic contamination has been previously reported at Kung Wiman Beach, located in Chanthaburi province along with the Eastern Gulf of Thailand. Our research aimed to study the microbial population of the sand and plastisphere and isolate microorganisms with potential plastic degradation activity. Plastic and sand samples were collected from Kung Wiman Beach for microbial isolation on agar plates. The plastic samples were identified by Fourier-transform infrared spectroscopy. Plastic degradation properties were evaluated by observing the halo zone on mineral salts medium (MSM) supplemented with emulsified plastics, including polystyrene (PS), polylactic acid (PLA), polyvinyl chloride (PVC), and bis (2-hydroxyethyl) terephthalate (BHET). Bacteria and fungi were identified by analyzing nucleotide sequence analysis of the 16S rRNA and internal transcribed spacer (ITS) regions, respectively. 16S and ITS microbiomes analysis was conducted on the total DNA extracted from each sample to assess the microbial communities. Of 16 plastic samples, five were identified as polypropylene (PP), four as polystyrene (PS), four as polyethylene terephthalate (PET), two as high-density polyethylene (HDPE), and one sample remained unidentified. Only 27 bacterial and 38 fungal isolates were found to have the ability to degrade PLA or BHET on MSM agar. However, none showed degradation capabilities for PS or PVC on MSM agar. Notably, Planococcus sp. PP5 showed the highest hydrolysis capacity of 1.64 ± 0.12. The 16S rRNA analysis revealed 13 bacterial genera, with seven showing plastic degradation abilities: Salipiger, Planococcus, Psychrobacter, Shewanella, Jonesia, Bacillus, and Kocuria. This study reports, for the first time of the BHET-degrading properties of the genera Planococcus and Jonesia. Additionally, The ITS analysis identified nine fungal genera, five of which demonstrated plastic degradation abilities: Aspergillus, Penicillium, Peacilomyces, Absidia, and Cochliobolus. Microbial community composition analysis and linear discriminant analysis effect size revealed certain dominant microbial groups in the plastic and sand samples that were absent under culture-dependent conditions. Furthermore, 16S and ITS amplicon microbiome analysis revealed microbial groups were significantly different in the plastic and sand samples collected. We reported on the microbial communities found on the plastisphere at Kung Wiman Beach and isolated and identified microbes with the capacity to degrade PLA and BHET.

Metabolomic and genomic insights into TMA degradation by a novel halotolerant strain - Paracoccus sp. PS1.

Trimethylamine N-oxide (TMAO) is a gut metabolite that acts as a biomarker for chronic diseases, and is generated by the oxidation of trimethylamine (TMA) produced by gut microflora. Since, microbial degradation of TMA is predicted to be used to restrict the production of TMAO, we aimed to isolate bacterial strains that could effectively degrade TMA before being oxidized to TMAO. As marine fish is considered to have a rich content of TMAO, we have isolated TMA degrading isolates from fish skin. Out of the fourteen isolates, depending on their rapid TMA utilization capability in mineral salt medium supplemented with TMA as a sole carbon and nitrogen source, isolate PS1 was selected as our desired isolate. Its TMA degrading capacity was further confirmed through spectrophotometric, Electrospray Ionization Time-of-Flight Mass Spectrometry (ESI TOF-MS) and High performance liquid chromatography (HPLC) analysis and in silico analysis of whole genome (WG) gave further insights of protein into its TMA degradation pathways. PS1 was taxonomically identified as Paracoccus sp. based on its 16S rRNA and whole genome sequence analysis. As PS1 possesses the enzymes required for degradation of TMA, clinical use of this isolate has the potential to reduce TMAO generation in the human gut.

Biosurfactant Activity of Bacillus sp. Strain LP04 Isolate and Its Antifungal Potency against Ganoderma boninense and Fusarium sp.

Biosurfactants are a class of amphipathic molecules that various microorganisms can produce. Biosurfactants are used as biopesticides and biocontrol agents because they have antimicrobial activity, especially as antifungal agents in several species of fungal pathogens such as Ganoderma boninense and Fusarium sp. that attack crops. This study aims to detect the biosurfactant activity of Bacillus sp. and its potential as an antifungal agent against the fungi Ganoderma boninense and Fusarium sp. Biosurfactants were produced in mineral salt medium (MSM) by harvesting cell-free supernatants. Screening of biosurfactant-producing isolates was carried out using an oil-spreading assay, a hemolysis assay, and an emulsification index. The antifungal activity of the isolates was then tested using the agar diffusion method. The LP04 isolate was closely related to Bacillus thuringiensis with a 99% similarity level. It has the potential to have biosurfactant activity, which is characterized by a positive result on the oil spreading assay test and has an emulsification index of 48.33±2.87%. The cell-free supernatants of the bacterial isolate were able to inhibit the growth of Ganoderma boninense and Fusarium sp. with growth inhibition rates of 51.11% and 56.92%, respectively.

Degradation of Dimethyl Phthalate and Diethyl Phthalate by Bacteria Isolated from Jazan, Saudi Arabia

P hthalate esters (PAEs) are commonly utilized in commercial, industrial, and medical applications. Various concentrations of PAEs have been detected in seawater samples and treated wastewater obtained from wastewater treatment plants in Saudi Arabia. Since these compounds pose adverse effects to human health, it is vital to develop efficient strategies to eliminate phthalate contamination from environments. In the present study, an enrichment technique was used to isolate phthalate-degrading bacteria from seawater and from activated sludge collected at Jazan Wastewater Treatment Plant, Saudi Arabia. Bacteria with the capability of degrading dimethyl phthalate (DMP) or diethyl phthalate (DEP) were isolated using minimum salt medium supplemented with these compounds as the sole carbon and energy source. High-performance liquid chromatography (HPLC) was utilized to evaluate the residual concentration of DMP and DEP. Using the 16S rRNA gene sequencing technique, the isolates with maximum DMP biodegradation activity were identified as Achromobacter sp. M1 and Pseudomonas sp. M2, while the isolates with maximum DEP biodegradation activity were identified as Pseudomonas sp. E2 and Pseudomonas sp. E3. The optimum bacterial growth was achieved at 30°C, pH 7.0, and 2% NaCl, except for Pseudomonas sp. E3, which demonstrated its maximum growth in the absence of NaCl. The highest biodegradation rate for all the bacterial strains (> 99.0%) was achieved at 30°C, pH 7.0, and up to 2% NaCl within 4 days. Concurrently, Pseudomonas sp. M2 and Pseudomonas sp. E2 exhibited remarkable degradation rates (97.5% and 56.7%, respectively) at 4% NaCl whereas Pseudomonas sp. E3 showed its highest DEP degradation (82.4%) after 4 days in the absence of NaCl. This study offers potential candidates, including Achromobacter sp. M1, Pseudomonas sp. M2, Pseudomonas sp. E2, and Pseudomonas sp. E3, for the proficient biodegradation of DMP and DEP.

Isolation, identification and transcriptome analysis of triadimefon-degrading strain Enterobacter hormaechei TY18.

Triadimefon, a type of triazole systemic fungicide, has been extensively used to control various fungal diseases. However, triadimefon could lead to severe environmental pollution, and even threatens human health. To eliminate triadimefon residues, a triadimefon-degrading bacterial strain TY18 was isolated from a long-term polluted site and was identified as Enterobacter hormaechei. Strain TY18 could grow well in a carbon salt medium with triadimefon as the sole nitrogen source, and could efficiently degrade triadimefon. Under triadimefon stress, a total of 430 differentially expressed genes (DEGs), including 197 up-regulated and 233 down-regulated DEGs, were identified in strain TY18 using transcriptome sequencing (RNA-Seq). Functional classification and enrichment analysis revealed that these DEGs were mainly related to amino acid transport and metabolism, carbohydrate transport and metabolism, small molecule and pyrimidine metabolism. Interestingly, the DEGs encoding monooxygenase and hydrolase activity acting on carbon-nitrogen were highly up-regulated, might be mainly responsible for the metabolism in triadimefon. Our findings in this work suggest that strain E. hormaechei TY18 could efficiently degrade triadimefon for the first time. They provide a great potential to manage triadimefon biodegradation in the environment successfully.

Exploring the potential of bacterial consortium for the treatment of paper mill effluent treatment through various treatment strategies and evaluation of their toxicity

Paper mill effluent containing kraft lignin (KL) and other toxic compounds poses serious environmental health concerns due to its potential for bioaccumulation. A prospective bacterial consortium is still needed for the remediation of paper mill effluent. Therefore, the current work aims to explore the potential of consortium, i.e. Bacillus cereus, B. paramycoides, and B. aryabhattai via different treatment strategies: batch, continuous, multipulse, and dissolved oxygen (DO) stat fed-batch for maximum detoxification of effluent under optimised conditions. A minimal salt medium containing 1.0 % glucose, 0.5 % ammonium nitrate, and pH 8.0 was the optimum condition for the consortium to degrade 1000 mg/L of kraft lignin in the effluent. Laboratory adaptation evolution (LAE) studies showed that the maximum number of bacterial generations was observed within 178 h at 5th cycle for 3000 mg/L kraft lignin. The maximum removal of KL, color, chemical oxygen demand (COD), biological oxygen demand (BOD), and total phenol by the dissolved oxygen stat fed-batch treatment strategy was 94 %, 86 %, 91 %, 90 %, and 97 %, respectively. Phytotoxicity testing of the consortium-treated effluent on Vigna radiata L., and Trigonella foenum-graecum L. revealed a reduction in phytotoxicity by ∼66 % and ∼68 %, respectively. The genotoxicity study on Allium cepa L. showed that the percent of aberrant cells with different chromosomal aberrations was decreased in consortium-treated effluent as compared to untreated effluent. This work provides a new insight and strategy for the paper mill effluent treatment at an industrial scale. Statement of environmental implicationThe paper mill effluent contains various hazardous compounds; chlorinated phenols, dioxins, kraft lignin, and endocrine disrupting compounds, when discharge from industries without proper treatment. This effluent causes mutagenic, clastogenic, carcinogenic, and endocrine-disrupting mechanisms in flora and fauna. This study provides a comparative performance evaluation of different treatment strategies: batch, continuous fed-batch, multipulse fed-batch, and dissolved oxygen stat fed-batch, for paper mill effluent treatment using a bacterial consortium for maximum removal of kraft lignin, color, chemical oxygen demand, total phenol concentration, and quantified ligninolytic enzyme production. Treated effluent showed a lesser phytotoxic and genotoxic effect. Therefore, the results of this study are suitable for environmental restoration. Significance of studyContrastingly, throughout this study, found that bacterial consortium have superior detoxifying qualities of paper mill effluent compared to pure cultures, via different treatment strategies: batch, continuous, multipulse, and dissolved oxygen stat fed-batch strategies under optimised conditions at lab scale. According to these results, such dissolved oxygen stat fed-batch strategy mediated treated effluent that promotes seed germination and showed a higher mitotic index of root cells of the plant in contrast to untreated effluent. Therefore, these treatment strategies are adequate, effective, and sustainable to reduce the significant pollution load in effluent.

A Rapid Continuous Flow Injection Analysis Method Development for Diphenhydramine Hydrochloride

Background: Diphenhydramine hydrochloride (DPH) is widely used as an antihistamine for treating various allergic conditions and symptoms. Traditional analytical methods for quantifying DPH often involve complex procedures and instrumentation. However, recent advancements in nanotechnology and analytical techniques offer opportunities for developing simpler and more efficient methods for DPH analysis. Method: This study presents a novel approach for quantifying DPH using continuous flow injection analysis (CFIA) combined with turbidimetric measurements. The precipitation reaction between DPH and 3,5-dinitro salicylic acid was utilized in an aqueous medium system. Various physical and chemical parameters were optimized, including the concentration of precipitating reagent, reaction medium (acids and salts), irradiation source intensity, volume of sample segment, and delay reaction coil. Results: Optimization of physical and chemical parameters revealed that a concentration of 15 m.mol/Liter for 3,5-dinitro salicylic acid, distilled water as the reaction medium, and an irradiation source intensity of 3.1 VDC produced optimal results. The linear dynamic range for DPH concentration was determined to be 0.01-20 m.mol/Liter. Comparison with the traditional UV-spectrophotometric method showed comparable results, indicating the reliability of the proposed CFIA method. Conclusion: The CFIA method presented in this study offers several advantages over traditional analytical methods for quantifying DPH in pharmaceutical formulations. It provides high sensitivity, speed, simplicity, and improved accuracy. The proposed approach has the potential for widespread application in pharmaceutical analysis, offering a cost-effective and easily manipulable solution for routine laboratory use. Overall, this study demonstrates a significant advancement in the measurement of DPH, which could simplify processes for pharmaceutical analysis and enhance industrial production levels.

SCREENING AND CHARACTERIZATION OF POTENTIAL CYPERMETHRIN-DEGRADING BACTERIA VIA PHENOTYPIC AND MOLECULAR TECHNIQUES

The need for sustainable management of cypermethrin, a widely used synthetic pesticide with significant ecological impact, calls for urgent concerns among environmental stakeholders. Therefore, in this study, the potential cypermethrin-degrading (PCD) bacteria were screened and identified from the soil samples collected from the Cowpea farm of Teaching and Research farm of Kwara State University, Nigeria. The bacterial strains were screened and isolated through enrichment techniques and identified using the standard phenotypic and molecular techniques. The potential for cypermethrin utilisation was determined in the cypermethrin-treated mineral salt medium. The three PCD bacterial strains isolated were PCD1 (Lysinibacillus fusiformis), PCD2 (Bacillus sonorensis), and PCD3 (Achromobacter sp.). Molecular characterization confirmed the identities and revealed high sequence similarity with known species. The accession numbers for these strains are MF973057 (PCD1), MF973058 (PCD2), and MF973059 (PCD3). The growth-dependent utilization of cypermethrin using the optical density values (OD 600 nm) showed the highest OD value on day six (PCD2: 0.60 and PCD3: 0.65) and day nine (PCD1: 0.80) respectively. The observed increases in optical density (OD 600 nm) affirmed their potential for cypermethrin degradation. While the strains exhibit promise in metabolizing cypermethrin, further research is needed to assess their suitability for bioremediation.

Establishment of a cobia (Rachycentron canadum) gill cell line: A valuable tool for immune response studies

Cobia (Rachycentron canadum), a commercially important marine fish, has been used to develop a novel gill cell line, designated CG, for the first time. The CG cell line was cultured in Leibovitz's-15 medium with 5% fetal bovine serum (FBS) and successfully sub-cultured more than 110 passages. It underwent verification through sequencing of the mitochondrial cytochrome C oxidase subunit I (COI) gene. Optimal growth rate was achieved when the CG cell line was cultured in a medium supplemented with 5% FBS, 1% Penicillin-Streptomycin (P/S), and 5 parts per thousand (ppt) of coral sea salt water, maintained at a temperature of 27 °C. The addition of 5 ppt of salt in the growth medium suggests that this cell line could be a viable in vitro tool for marine ecosystem toxicological studies or for culturing marine parasitic microorganisms. The CG cell line was also successfully transfected using the pTurbo-GFP plasmids, showing an 18% efficiency, with observable GFP expression. Furthermore, the cell line has been effectively cryopreserved. Gene expression analysis indicated that the CG cell line exhibits responsive regulation of immune gene expression when exposured to various stimulants, highlighting its potential as an in vitro platform for immune response studies. This makes it suitable for exploring dynamic immune signaling pathways and host-pathogen interactions, thereby offering valuable insights for therapeutic development.

Biodegradation of polystyrene and polyethylene by Microbacterium esteraromaticum SW3 isolated from soil

Plastic pollution is a common concern of global environmental pollution. Polystyrene (PS) and polyethylene (PE) account for almost one-third of global plastic production. However, so far, there have been few reports on microbial strains capable of simultaneously degrading PS and PE. In this study, Microbacterium esteraromaticum SW3, a non-pathogenic microorganism that can use PS or PE as the only carbon source in the mineral salt medium (MM), was isolated from plastics-contaminated soil and identified. The optimal growth conditions for SW3 in MM were 2% (w/v) PS or 2% (w/v) PE, 35°C and pH 6.3. A large number of bacteria and obvious damaged areas were observed on the surface of PS and PE products after inoculated with SW3 for 21 d. The degradation rates of PS and PE by SW3 (21d) were 13.17% and 5.39%, respectively. Manganese peroxidase and lipase were involved in PS and PE degradation by SW3. Through Fourier infrared spectroscopy detection, different functional groups such as carbonyl, hydroxyl and amidogen groups were produced during the degradation of PS and PE by SW3. Moreover, PS and PE were degraded into alkanes, ketones, carboxylic acids, esters and so on detected by GC-MS. Collectively, we have isolated and identified SW3, which can use PS or PE as the only carbon source in MM as well as degrade PS and PE products. This study not only provides a competitive candidate strain with broad biodegradability for the biodegradation of PS and/or PE pollution, but also provides new insights for the study of plastic biodegradation pathways.

Microbial-based metabolites associated with degradation of imidacloprid and its impact on stress-responsive proteins.

Imidacloprid (IMD), a neonicotinoid insecticide, is intensively used in agricultural fields for effective protection against aphids, cane beetles, thrips, stink bugs, locusts, etc., is causing serious environmental concerns. In recent years, seed treatment with Imidacloprid is being practiced mainly to prevent sucking insect pests. In India, due to the increase in application of this insecticide residue has been proven to have an impact on the quality of soil and water. In view of this, the current investigation is focussed on sustainable approach to minimize the residual effect of IMD in agricultural fields. The present study reveals a most promising imidacloprid resistant bacterium Lysinibacillus fusiformis IMD-Bio5 strain isolated from insecticide-contaminated soil. The isolated bacterial strain upon tested for its biodegradation potential on mineral salt medium (MSM) showed a significant survival growth at 150g/L of IMD achieved after 3 days, whereas immobilized cells on MSM amended with 200g/L of IMD as the sole carbon source provided degradation of 188 and 180g/L of IMD in silica beads and sponge matrices, respectively. The liquid chromatography mass spectrometry was performed to test the metabolite responsive for IMD biodegradation potential of L. fusiformis IMD-Bio5 which showed the induced activity of the metabolite 6-Chloronicotinic acid. Furthermore, as compared to the untreated control, the Lysinibacillus fusiformis IMD-Bio5 protein profile revealed a range of patterns showing the expression of stress enzymes. Thus, results provided a most effective bacterium enabling the removal of IMD-like hazardous contaminants from the environment, which contributes to better agricultural production and soil quality, while long-term environmental advantages are restored.

Corrosion and inhibition studies on AISI 316 with AISI 410 fiber laser welded joints

In this investigation, the corrosion study was conducted on fiber laser welded joints of AISI 410 and 316L stainless steel plates using hydrochloric acid, basic, and salt medium, behavior in three different pH. The effects of three different corrosive atmospheres were examined using the weight loss method. The test sample which was exposed to 1 N hydrochloric acid medium for 48 Hours resulted in 0.006 g of weight loss. The maximum amount of corrosion was found in the acidic medium whereas the least was observed in the salt medium. The effectiveness of three distinct derivatives of 1H-indole-2,3-dione, each replaced with hydroxyl groups in various positions, in inhibiting corrosion. Among the three derivatives examined, it was observed that those with ortho and para hydroxyl group substitutions exhibited superior inhibitory properties.
 KEY WORDS: Fiber laser welding, Traverse speed, Corrosion study, Isatin Schiff base, Inhibitors
 Bull. Chem. Soc. Ethiop. 2024, 38(3), 811-823. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i3.20

Polystyrene degradation by bacteria isolated from the larvae of <i>Rhynchophorusphoenicis</i>

The larvae of insects of the order Coleoptera have been reported to biodegrade plastics aided by their chewing mouthparts and the activities of their gut biota. However, there is no report of this ability by the African palm weevil (Rhynchophorus phoenicis). This study aims to the ability of R. phoenicis larvae to biodegrade polystyrene (PS). A total of 100 R. phoenicis larvae were fed for 21 days with PS foam, and afterwards, the gut contents of survivors were investigated for possible PS-degrading bacteria. Bacterial isolates were screened for PS biodegradation in an Erlenmeyer flask with PS film as the sole carbon source, in a mineral salt medium (MSM) at a temperature of 30oC and a pH of 7, for a period of 28 days. The isolates were used for biodegradation assay under the same conditions, for 60 days. The weight of PS films was determined before and after the biodegradation assay. Chemical changes in the films were confirmed by Fourier Transform Infrared (FTIR) spectroscopy. Two bacterial isolates were recovered from the gut of the only surviving R. phoenicis larvae fed with 100% PS. The isolates were identified based on their 16S rRNA sequences as Lysinibacillus macriodes and Pantoea dispersa with accession numbers OQ652017 and OQ652023 respectively. The isolates caused an 8.8% reduction in the weight of PS film and FTIR spectroscopy results confirmed the formation of groups suggestive of degradation products with the carbonyl group showing up as absorption peaks in the range of 1640-1760 cm-1 and the hydroxylic group at 3000-3700 cm-1 . The isolates were able to produce polyhydroxyalkanoate (PHA) equivalent to 1.4g/L, under PS degradation conditions. Therefore, coupling the biodegradation of PS with PHAproduction could be useful for the valorization of PS waste.