Continuous Cr(VI) removal by Scenedesmus incrassatulus in an airlift photobioreactor

Cr(VI) removal by Scenedesmus incrassatulus was characterized in a continuous culture system using a split-cylinder internal-loop airlift photobioreactor fed continuously with a synthetic effluent containing 1.0 mg Cr(VI) l^?1 at dilution rate (D) of 0.3 d^?1. At steady state, there was a small increase (6%) on the dry biomass (DB) concentration of Cr(VI)-treated cultures compared with the control culture. 1.0 mg Cr(VI) l^?1 reduced the photosynthetic pigments content and altered the cellular morphology, the gain in dry weight was not affected. At steady state, Cr(VI) removal efficiency was 43.5 ± 1.0% and Cr(VI) uptake was 1.7 ± 0.1 mg Cr(VI) g^?1 DB. The system reached a specific metal removal rate of 458 μg Cr(VI) g^?1 DB d^?1, and a volumetric removal rate of 132 μg Cr(VI) l^?1 d^?1.     

Chenopodium album extract ameliorates carbon tetrachloride induced hepatotoxicity in rat model

Major objective of this study was to explore the protective effect of the methanolic extract of Chenopodium album against carbon tetrachloride induced hepatotoxicity in rats. Chenopodium album has locally been used for multiple medicinal proposes. Methanolic extract of Chenopodium album (whole plant) was prepared with Soxhlet extractor and rotatory evaporator. Antioxidant activity of Chenopodium album was determined by DPPH free radical scavenging assay. Thirty Wister (albino) rats (150–200 g) were divided into six groups for the evaluation of hepatoprotective potential of different concentrations of Chenopodium album against carbon tetrachloride (1:1 CCl₄: Olive oil) under the controlled laboratory conditions. Group-I rats were administrated with olive oil (Normal control), Group-II with CCl₄ only, Group-III with Silymarin (positive control), Group-IV with Chenopodium album (100 mg/kg), Group-V with Chenopodium album (200 mg/kg) and Group-VI rats with Chenopodium album (300 mg/kg) for the period of 28 days. Serum was taken to determine the levels of alanine transaminase, aspartate transaminase, alkaline phosphatase, cholesterol, triglyceride, creatinine and urea in the blood. Formalin stored tissues were examined for histopathological analysis. DPPH assay showed that Chenopodium album has the potential for reduction of oxidative stress. Chenopodium album minimized the levels of ALT (70 ± 8.68 U/L, 68.75 ± 8.38 U/L & 73.5 ± 10.28 U/L), AST (219.5 ± 19.16 U/L, 140.75 ± 13.35 U/L & 221.25 ± 13.33 U/L) and ALP (289.5 ± 28.21 U/L, 258 ± 11.12 U/L & 248.25 ± 4.03 U/L) at different concentrations (100 mg/kg, 200 mg/kg, 300 mg/kg respectively). Chenopodium album enhanced triglyceride level (64.75 ± 12.66 mg/dl at 200 mg/kg) as compared to CCl₄ treated group (33.25 ± 1.26 mg/dl). Carbon tetrachloride elevated urea level (43.25 ± 6.6) was decreased by high dose of Chenopodium album (18 ± 8.17). Moreover, Chenopodium album also improved WBC level (9.69 × 10³ /Cu.mr & 10.59 × 10³ /Cu.mr at low and medium doses respectively), RBCs level (6.97 × 10³ /Cu.mr) and hemoglobin level (13.95 G/dL, 13.467 G/dL & 14.05 G/dL at low, medium and high doses). In vivo study of Chenopodium album methanolic extract demonstrates the potential for protection of liver and after pre-clinical studies the plant can be used as a safe alternative of commercially available hepatoprotective medicines.     

Enhancement of hexavalent chromium reduction and electricity production from a biocathode microbial fuel cell

Enhancement of Cr (VI) reduction rate and power production from biocathode microbial fuel cells (MFCs) was achieved using indigenous bacteria from Cr (VI)-contaminated site as inoculum and MFC architecture with a relatively large cathode-specific surface area of 340–900 m² m⁻³. A specific Cr (VI) reduction rate of 2.4 ± 0.2 mg g⁻¹VSS h⁻¹ and a power production of 2.4 ± 0.1 W m⁻³ at a current density of 6.9 A m⁻³ were simultaneously achieved at an initial Cr (VI) concentration of 39.2 mg L⁻¹. Initial Cr (VI) concentration and solution conductivity affected Cr (VI) reduction rate, power production and coulombic efficiency. These findings demonstrate the importance of inoculation and MFC architecture in the enhancement of Cr (VI) reduction rate and power production. This study is a beneficial attempt to improve the efficiency of biocathode MFCs and provide a good candidate of bioremediation process for Cr (VI)-contaminated sites.     

N-Acetyl-L-Cysteine Protects Liver and Kidney Against Chromium(VI)-Induced Oxidative Stress in Mice

Acute hexavalent chromium [Cr(VI)] compound exposure may lead to hepatotoxic and nephrotoxic effects. Cr(VI) reduction may generate reactive intermediates and radicals which might be associated with damage. We investigated effects of N-acetyl-l-cysteine (NAC) pre- or post-treatment on oxidative stress and accumulation of Cr in liver and kidney of Cr(VI)-exposed mice. Intraperitoneal potassium dichromate injection (20 mg Cr/kg) caused a significant elevation of lipid peroxidation in both tissues as compared to control (p < 0.05). Significant decreases in non-protein sulfhydryl (NPSH) level, as well as enzyme activities of catalase (CAT) and superoxide dismutase (SOD) along with significant accumulation of Cr in the tissues (p < 0.05) were of note. NAC pre-treatment (200 mg/kg, ip) provided a noticeable alleviation of lipid peroxidation (p < 0.05) in both tissues, whereas post-treatment exerted significant effect only in kidney. Similarly, Cr(VI)-induced NPSH decline was restored by NAC pre-treatment in both tissues (p < 0.05); however, NAC post-treatment could only replenish NPSH in liver (p < 0.05). Regarding enzyme activities, in liver tissue NAC pre-treatment provided significant restoration on Cr(VI)-induced CAT inhibition (p < 0.05), while SOD enzyme activity was regulated to some extent. In kidney, SOD activity was efficiently restored by both treatments (p < 0.05), whereas CAT enzyme alteration could not be totally relieved. Additionally, NAC pre-treatment in both tissues and post-treatment in liver exerted significant tissue Cr level decreases (p < 0.05). Overall, especially NAC pre-treatment seems to provide beneficial effects in regulating pro-oxidant/antioxidant balance and Cr accumulation caused by Cr(VI) in liver and kidney. This finding may be due to several mechanisms including extracellular reduction or chelation of Cr(VI) by readily available NAC.     

Pharmacological intervention of biosynthesized Nigella sativa silver nanoparticles against hexavalent chromium induced toxicity in male albino mice

Hexavalent chromium, toxic heavy metal, among the top-rated environmental contaminants, is declared a potent endocrine disruptor in humans and animals. The present study was planned to find harmful effects on the reproductive system caused by Cr (VI) and the ameliorative effect of Nigella sativa and Nigella sativa-mediated AgNP on male mice (Mus musculus). In the present study, known infertility medicine, clomiphene citrate is also used as a positive control. The main objective of the present study was to assess the ameliorative potential of oral administration of a dose of 50 mg/kg BW clomiphene citrate (control), AgNP via chemical synthesis, Nigella sativa seed extract, and Nigella sativa-mediated AgNP against the Cr (VI) at the dose of 1.5 mg/kg BW from K₂Cr₂O₇ orally induced toxicity over eight weeks on the reproductive performance of male albino mice. Nigella sativa mediated AgNPs were characterized by UV, SEM, FTIR, and XRD. The histological analysis, smear study, antioxidant capacity test, and hormone analysis were conducted by blood samples of albino mice. Cr exposed groups showed a significant decrease in sperm head breadth (5.29 ± 0.54 µ) and length (19.54 ± 1.18 µ), middle piece length, tail length, LH (1.65 ± 0.15 ng/mL), testosterone (2.63 ± 0.29 ng/mL), SOD (61.40 ± 2.48 mmol/mL), CAT (87.40 ± 6.01 mmol/mL), GSH (1.54 ± 0.09 µmol/mL), and no of spermatogonia (1.22 ± 0.25), and spermatocytes (2.33 ± 0.943). However, FSH level (160.00 ± 4.98 ng/mL), seminiferous tubule CSA (1094.69 ± 49.76 mm²), size of spermatogonia (41.30 ± 1.24 µ), and spermatocytes (26.07 ± 1.34 µ) were significantly increased. Administration of Nigella sativa and Nigella sativa-mediated AgNPs reduced the toxicity.     

Quercetin protects mouse oocytes against chromium-induced damage in vitro and in vivo

BackgroundChromium (Cr) is a naturally-occurring element that is used in various fields of industry. Humans may be exposed to hexavalent chromium [Cr(VI)], which is one of the stable valence states of the chromium through contaminated soil, air, and water. Exposure to Cr(VI) through contaminated drinking water, soil and air causes various cancers and also fertility problems in animals and humans. Quercetin (QCT), a common flavonoid compound, has numerous biological effects as an antioxidant and free radical scavenger, but its function and mechanisms in reproductive processes in various species remain unclear. This study aims to determine the chromium effects on mice oocyte quality and the ameliorative effect of QCT in both in vitro and in vivo experimental models.MethodsFor the in vitro experiment, oocytes were collected and divided into the control, sham, QCT-treated, Cr(VI) (potassium dichromate), and treatment [Cr(VI)+QCT] groups. Collected oocytes were cultured in maturation medium with or without 10 µM quercetin and 10 µM Cr(VI) for 14 h based on the defined experimental design. For the in vivo experiment, the mice were randomly divided into the control, sham, QCT-treated, Cr(VI), and Cr(VI) + QCT groups. Control and sham mice received regular drinking water and diet. Cr(VI) group received Cr(VI) (50 ppm in drinking water) and Cr(VI) + QCT group received 50 ppm Cr(VI) with QCT (20 mg/kg body wt, through i.p) for a period of 21 days and then oocytes were collected and cultured for 14 h for in vitro maturation. For both experiments, at the end of the culture period, we examined the ameliorative effect of QCT on oocyte maturation, spindle formation, ROS production, mitochondrial function, and apoptosis.ResultsOur in vitro and in vivo results showed that Cr(VI) disrupt the oocyte maturation and spindle formation (P < 0.001). Furthermore, we found that exposure to Cr(VI) significantly increased ROS levels and decreased mitochondrial membrane potential (P < 0.001). In addition, exposure to Cr(VI) induced early apoptosis and downregulated the Bcl-2 mRNA expression and upregulated the Caspase-3 and Bax mRNAs expression (P < 0.01). Finally, quercetin significantly restored the detrimental effects of Cr(VI).ConclusionThe results indicated that quercetin protects the oocytes against Cr(VI) toxicity through the suppression of oxidative stress and apoptosis. The conclusions drawn from our study's findings suggest that quercetin might be useful agent for oocyte maturation in case of possible exposure to toxic substances such as chromium.     

Uranium(VI) bioprecipitation mediated by a phosphate solubilizing Acinetobacter sp. YU-SS-SB-29 isolated from a high natural background radiation site

Bioprecipitation of uranium (U) into uranyl phosphate (U-P) mediated by soluble ortho-phosphate is an attractive proposition for U bioremediation. As an alternative to the microbial phosphatase, we have investigated the dissolution of phosphate by the organic acids produced by bacteria to aid in U precipitation. The bacterium Acinetobacter sp. YU-SS-SB-29, isolated from monazite sand of natural background radiation site solubilized 952.0 ± 46.7 mg L⁻¹ phosphate from tri-calcium phosphate (TCP) in the Pikovskaya's medium and showed tolerance to 120 ppm U(VI). U(VI) bioprecipitation was investigated by adding different concentrations of U(VI) to a cell-free culture supernatant containing ortho-phosphate released from TCP by the bacterium. A yellow precipitate was immediately formed following which there was a reduction in U(VI) concentration. A strong positive correlation (R² = 0.98) was observed between % decrease in phosphate and U(VI) concentration (up to 750 ppm U) added. FTIR and EDX spectra of the yellow precipitate demonstrated the involvement of phosphate groups in U(VI) binding. Furthermore, the XRD pattern of the precipitate agrees well with that of chernikovite, a uranyl phosphate mineral. The results from this study demonstrate the potential of the U tolerant, phosphate solubilizing bacterium Acinetobacter sp. YU-SS-SB-29 for non-reductive in situ bioprecipitation of uranium.     

Efficacy of bacterial consortium-AIE2 for contemporaneous Cr(VI) and azo dye bioremediation in batch and continuous bioreactor systems, monitoring steady-state bacterial dynamics using qPCR assays

Bacterial consortium-AIE2 with a capability of contemporaneous Cr(VI) reduction and azo dye RV5 decolourization was developed from industrial wastewaters by enrichment culture technique. The 16S rRNA gene based molecular analyses revealed that the consortium bacterial community structure consisted of four bacterial strains namely, Alcaligenes sp. DMA, Bacillus sp. DMB, Stenotrophomonas sp. DMS and Enterococcus sp. DME. Cumulative mechanism of Cr(VI) reduction by the consortium was determined using in vitro Cr(VI) reduction assays. Similarly, the complete degradation of Reactive Violet 5 (RV5) dye was confirmed by FTIR spectroscopic analysis. Consortium-AIE2 exhibited simultaneous bioremediation efficiencies of (97.8 ± 1.4) % and (74.1 ± 1.2) % in treatment of both 50 mg l⁻¹ Cr(VI) and RV5 dye concentrations within 48 h of incubation at pH 7 and 37°C in batch systems. Continuous bioreactor systems achieved simultaneous bioremediation efficiencies of (98.4 ± 1.5) % and (97.5 ± 1.4) % after the onset of steady-state at 50 mg l⁻¹ input Cr(VI) and 25 mg l⁻¹ input RV5 concentrations, respectively, at medium dilution rate (D) of 0.014 h⁻¹. The 16S rRNA gene copy numbers in the continuous bioreactor as determined by real-time PCR assay indicated that Alcaligenes sp. DMA and Bacillus sp. DMB dominated consortium bacterial community during the active continuous bioremediation process.     

Biosorption of trivalent and hexavalent chromium from aqueous systems using shelled Moringa oleifera seeds

Abstract

The present study explores the sorption properties of shelled Moringa oleifera seeds (SMOS) for removal of two environmentally important oxidation states of chromium (trivalent and hexavalent) from an aqueous system on the laboratory scale. Sorption studies reveal the optimum conditions for the removal of 81.02%; Cr (III) and 88.15% Cr (VI) as follows: biomass dosage (4.0 g), metal concentration [25mg/L for Cr (III); 50mg/L for Cr (VI)], contact time (40 minutes) at pH 6.5 and 2.5 respectively. The adsorption data were found to fit well both the Freundlich and Langmuir isotherms. Characterization of the seed powder by FTIR showed the clear presence of amino acid moieties having both positively charged amino and negatively charged carboxylic groups and confirmed that biosorption involves amino acid-chromium interactions. SEM studies of native and exhausted [Cr(III) and Cr(VI)] treated SMOS revealed large spherical clusters having a pore area of 8.66 µm² in the case of native SMOS while dense agglomerated etched dendrite type morphology have a pore area of 0.80 µm² in Cr (III) and 0.78 µm² in Cr (VI) treated SMOS The spent biosorbent was regenerated and found to be effectively reusable for four cycles.     

Role of insulin in Cr(VI)-mediated genotoxicity in Neurospora crassa

Aims: Chromium (III) is an insulinomimetic agent whose biological and/or environmental availability is frequently in the form of Cr(VI), which is known to be toxic. Wall‐less mutant of Neurospora crassa (FGSC stock no. 4761) is known to possess insulin receptor in its cell membrane and hence is a good model for Cr toxicity studies. This study explores the toxicity of Cr(VI) and the possible consequences on simultaneous exposure to insulin in N. crassa. Methods and Results: Comet assay of N. crassa cells treated with 100 μmol l^?1 Cr(VI) showed up to 50% reduction in comet tail lengths when incubated simultaneously with 0·4 U insulin. Fluorescence measurement in Cr(VI)‐treated cells using DCFH‐DA showed six‐ to eightfold increase in free radical generation, which was reduced to fourfold by 0·4 U insulin. Annexin‐V/PI Flow cytometry analysis indicated necrotic cell death up to 28·7 ± 3·6% and 68·6 ± 2·5% on Cr(VI) exposure at concentrations 100 and 500 μmol l^?1 which was reduced by 68·3 ± 3·2% and 48·9 ± 3·6%, respectively, upon addition of insulin. Conclusion: Insulin‐mediated protection from DNA damage by Cr(VI) is because of scavenging of free radicals liberated during exposure to Cr(VI). Significance and Impact of the Study: Overall, Cr(VI) toxicity depends upon available insulin, indicating that Cr(VI) toxicity may be a serious issue in insulin‐deficient individuals with diabetes.     

Onosma hispidum L. extract reverses hyperlipidemia,hypertension, and associated vascular dysfunction in rats

Onosma hispidum.L (O. hispidum) belongs to the family Boregineacea. A preliminary study and its medicinal use suggested its role in the management of hyperlipidemia. The present study aimed to assess the effect of methanolic root extract of O. hispidum in hyperlipidemia and associated vascular dysfunction. Oral administration of O. hispidum crude extract (Oh. Cr) to tyloxopol and high fat diet-induced hyperlipidemic Sprague-Dawley rats for 10 and 28 days significantly reduced total triglycerides and cholesterol (p < 0.001), compared to hyperlipidemic rats. Oh. Cr 250 mg/kg orally treated rats significantly (p < 0.001) reduced both the total body weight and atherogenic index in tylaxopol and HFD rats. In HMG-CoA assay, the inhibition of the enzyme was significant in Oh.Cr (250 mg/kg) treated group. Histopathological studies indicated that the group treated with Oh.Cr 250 mg/kg/day showed regular morphology of aortic intima, media and adventitia, and improved the endothelial damage. To investigate the vascular dysfunction, isolated rat aorta rings from all groups were pre-contracted with 1 µM phenylephrine (PE), and the effect of acetylcholine (Ach) was monitored. In the aorta isolated from Oh.Cr (50 mg/kg) treated group, Ach completely relaxed the PE-induced contraction with EC₅₀ value of 0.05 µg/mL 0.015 (0.01–0.2) compared to the hyperlipidemic control group (<30% relaxation). In atorvastatin (10 mg/kg) treated rat aorta, Ach showed 50% relaxation. The Oh.Cr extract also reduced (105.92 ± 1.14 to 66.63 ± 0.85 mmHg) mean arterial pressure in hyperlipidemic hypertensive rats. These findings suggest that extract of O. hispidum is an effective remedy for hypercholesterolemia, and hypertriglyceridemia, which acts through inhibition of HMG-CoA and improving vascular dysfunction.     

Chromium(III) tris(picolinate) is mutagenic at the hypoxanthine (guanine) phosphoribosyltransferase locus in Chinese hamster ovary cells

Chromium trispicolinate (CrPic) is a popular dietary supplement that is not regulated by the Food and Drug Administration. We are using this compound as a bio-available model to explore the role of Cr(III) in Cr(VI)-induced cancers. The ability of CrPic to cause mutations at the hypoxanthine (guanine) phosphoribosyltransferase (hprt) locus of CHO AA8 cells has been measured after a 48 h exposure. The highest dose tested was 80 μg/cm² CrPic, which, if fully soluble, would be equivalent to 1 mM or 0.44 mg/ml CrPic, and would correspond to 1 mM Cr(III) or 52 μg/ml Cr(III). This exposure resulted in 68±16% cell survival based on 48 h cell counts, and 24±11% survival by 7-day colony formation. Exposure of CHO cells to CrPic produced a statistically significant increase in 6-thioguanine (6-TG)-resistant cells over the dose range tested. The 80 μg/cm² CrPic exposure resulted in an average induced mutation frequency (MF) of 58 per 10⁶ surviving cells, or an average 40-fold increase in hprt mutants relative to untreated cells. An equivalent dose of 3 mM Pic was highly cytotoxic and did not yield hprt mutants. The dose range of 0.375–1.5 mM Pic produced a slight increase in hprt mutants, but the increase was not statistically significant. An equivalent dose of 1 mM chromic chloride yielded an induced MF of 9 per 10⁶ surviving cells, or a 10-fold increase in mutants with cell survivals of >100%. The coordination of Cr(III) with picolinic acid may make the metal more genotoxic than other forms of Cr(III). In light of the current results and the known ability of Cr(III) and CrPic to accumulate in tissues, as well as the growing evidence of Cr(III) involvement in Cr(VI)-induced cancers, we caution against ingestion of large doses of CrPic for extended periods.     

Isolation and screening of Streptomyces sp. Al-Dhabi-49 from the environment of Saudi Arabia with concomitant production of lipase and protease in submerged fermentation

In this study, Streptomyces sp. Al-Dhabi-49 was isolated from the soil sample of Saudi Arabian environment for the simultaneous production of lipase and protease in submerged fermentation. The process parameters were optimized to enhance enzymes production. The production of protease and lipase was found to be maximum after 5 days of incubation (139.2 ± 2.1 U/ml, 253 ± 4.4 U/ml). Proteolytic enzyme increases with the increase in pH up to 9.0 (147.2 ± 3.6 U/ml) and enzyme production depleted significantly at higher pH values. In the case of lipase, production was maximum in the culture medium containing pH 8.0 (166 ± 1.3 U/ml). The maximum production of protease was observed at 40 °C (174 ± 12.1 U/ml) by Streptomyces sp. Lipase activity was found to be optimum at the range of temperatures (30–50 °C) and maximum production was achieved at 35 °C (168 ± 7.8 U/ml). Among the evaluated carbon sources, maltose significantly influenced on protease production (218 ± 12.8 U/ml). Lipase production was maximum when Streptomyces sp. was cultured in the presence of glucose (162 ± 10.8U/ml). Among various concentrations of peptone, 1.0% (w/v) significantly enhanced protease production. The lipase production was very high in the culture medium containing malt extract as nitrogen source (86 ± 10.2 U/ml). Protease production was maximum in the presence of Ca²⁺ as ionic source (212 ± 3.8 U/ml) and lipase production was enhanced by the addition of Mg²⁺ with the fermentation medium (163.7 ± 6.2 U/ml).     

Moderate selenium dosing inhibited chromium (VI) toxicity in chicken liver

This study aimed to clarify the effect of selenium (Se) on chromium (VI) [Cr(VI)]‐induced damage in chicken liver. A total of 105 chickens were randomly divided into seven groups of 15. Group I received deionized water; group II received Cr(VI) (7.83 mg/kg/d) alone; and other groups orally received both Cr(VI) (7.83 mg/kg/d) and Se of different doses (0.14, 0.29, 0.57, 1.14, and 2.28 mg/kg/d). The levels of superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), Ca²⁺‐ATPase, and mitochondrial membrane potential (MMP) were measured. Results showed that Cr(VI) increased MDA content and decreased GSH content, T‐SOD activity, Ca²⁺‐ATPase activity, and MMP level. Meanwhile, Se co‐treatment (0.14, 0.29, and 0.57 mg/kg/d) increased the viability of the above indicators compared with Cr(VI)‐treatment alone. In addition, histopathologic examination revealed that Cr(VI) can cause liver damage, whereas Se supplementation of moderate dose inhibited this damage. This study confirmed that Se exerted protective effect against Cr(VI)‐induced liver damage.     

Insecticidal and acetylcholinesterase inhibitory activities of Achillea biebersteinii essential oil and its nanoemulsion and major monoterpenes against Tribolium castaneum

Essential oil (EO) was hydrodistilled from Achillea biebersteinii and analyzed using gas chromatography–flame ionization detection (GC–FID) and (GC–MS). Three monoterpenes, α-terpinene, p-cymene, and camphor were isolated as the main terpenes in the EO. Oil-in-water nanoemulsion (particle size 52.7 ± 4.4 nm) was prepared and characterized from EO through a hydrothermal approach. The EO products caused insecticidal effects and altered F₁ progeny of the red flour beetle, Tribolium castaneum (Herbst) in a dose and exposure time-dependent manner. The nanoemulsion was superior in bioactivity, followed EO. At 12.5 µl/cm², nanoemulsion and EO caused 100% mortality of the second larvae after 4 days of exposure with reduction of F₁ progeny of 100.0 and 89.2%, respectively. At 50.0 µl/cm², percentage mortality and reduction in progeny of EO products ranged between (61.4–100%) and (53.0–100%), respectively. Upon fumigation, nanoemulsion at 10 µl/L air caused 100% mortality of the second larvae after 4 days of exposure. At 20 µl/L air and 4 days after treatment, percentage mortality with the remainder botanicals ranging between 64.7 and 100. LC₅₀′s of products after 48 h exposure ranging between 6.7 and 58.1 µg/cm² in insecticidal bioassay, and between 3.6 and 26.3 µl/L upon fumigation. Botanicals caused a remarkable inhibition of acetylcholinesterase activity (AChE), where nanoemulsion (IC₅₀ = 14.22 mM), EO (IC₅₀ = 35.12 mM) and camphor (IC₅₀ = 23.93 mM) were superior as AChE inhibitors. There is a potential for using of A. biebersteinii EO, its nanoemulsion and monoterpenes as natural grain protectants after the required toxicological investigations.     

Detoxification and accumulation of chromium from tannery effluent and spent chrome effluent by Paecilomyces lilacinus fungi

The tannery industry process involves chromium (Cr) salts as a main constituent of the process. The Cr recovery is a part of the process where other salts are used to achieve separation and recovery for using Cr back in the process. The process steps may contain both forms of Cr [Cr(VI): hexavalent and Cr(III): trivalent]. The recovery of Cr from tannery industry effluent through biological systems is much needed. The diverse physicochemical characteristics of these effluents may limit the growth of microorganisms and hence the limitation towards possible practical application of microorganisms in real industrial effluent conditions. The present study attempted the ability of the Cr-resistant fungus Paecilomyces lilacinus [isolated through an enrichment culture technique at 25 000 mg l⁻¹ of Cr(III)] to grow and remove Cr [Cr(VI) and Cr(III)] from two physicochemically different undiluted tannery industry effluents (tannery effluent and spent chrome effluent) in the presence of cane sugar as a carbon source. Such attempts are made keeping in view the potential integration of biological processes in the overall Cr removal and recovery processes to improve its efficiency and environmental sustainability. The fungus has broad pH tolerance range and can reduce Cr(VI) both in acidic (pH 5.5) and alkaline (pH 8.0) conditions. The fungus showed the ability to remove Cr(VI) (1.24 mg l⁻¹) and total Cr (7.91 mg l⁻¹) from tannery effluent below the detection level within 18 h and 36 h of incubation, respectively, and ability to accumulate 189.13 mg Cr g⁻¹ of dry biomass within 600 h of incubation from spent chrome effluent [containing 3731.4 mg l⁻¹ of initial Cr(III) concentration].At 200 mg l⁻¹ of Cr(VI) in growth media, with 100% detoxification and with only 10.54% of total Cr accumulation in the biomass, P. lilacinus showed Cr(VI) reduction as a major mechanism of Cr(VI) detoxification. The time-course study revealed the log phase of the growth for the maximum specific reduction of Cr(VI) and stationary phase of the growth for its maximum specific accumulation of both the forms of Cr [Cr(III) and Cr(VI)] in its biomass. In growth media at 50 mg l⁻¹ and 200 mg l⁻¹ of Cr(VI), P. lilacinus showed 100% reduction within 36 h and 120 h of incubation, respectively. The high degree of positive correlation and statistically high degree of relationship (r² = 0.941) between the fungal growth and % Cr(VI) reduction by the fungus support the role of metabolically active cellular growth in Cr(VI) reduction by the fungus. Results indicate that expanded solid (sludge) retention times (SRTs) (stationary phase) can be recommended for the removal of Cr(III) through accumulation. In case of Cr(VI), reduction needs a priority; therefore, a non-expanded SRT is recommended for designing a continuous-flow completely stirred bioreactor so that a log phase of cellular growth can be maintained during the reduction process. This study reveals the strong potential of P. lilacinus fungi for the removal of Cr from tannery effluent and spent chrome effluent.     

Performance evaluation of various bioreactors for the removal of Cr(VI) and organic matter from industrial effluent

Performances of various bioreactors under different operating conditions were evaluated with respect to hexavalent chromium (Cr(VI)) reduction and COD removal. Continuous reactor studies were carried out with (i) aerobic suspended growth system, (ii) aerobic attached growth system, and (iii) anoxic attached growth system, using both synthetic and actual industrial wastewater. Arthrobacter rhombi-RE (MTCC7048), a Cr(VI) reducing strain enriched and isolated from chromium contaminated soil, was used in all the bioreactors for Cr(VI) biotransformation and COD removal. Aerobic and anoxic batch experiments were conducted to evaluate the bio-kinetic parameters. The bio-kinetic parameters for aerobic system were: μ_max = 2.34/d, K_s = 190 mg/L (as COD), K_i = 3.8 mg/L of Cr(VI), and Y_T = 0.377. These parameters for anoxic conditions were: μ_max = 0.57/d, K_s = 710 mg/L (as COD), K_i = 8.77 mg/L of Cr(VI), and Y_T = 0.13. Aerobic attached growth system, operated at a hydraulic retention time (HRT) of 24 h and an organic loading rate (OLR) of 3 kg/m³/d, performed better than aerobic suspended and the anoxic attached growth systems operated under identical conditions, while treating synthetic wastewater as well as industrial effluent.     

Estimates of heavy metal tolerance and chromium(VI) reducing ability of Pseudomonas aeruginosa CCTCC AB93066: chromium(VI) toxicity and environmental parameters optimization

The potential role of parameters in the reduction of hexavalent chromium [Cr(VI)] by Pseudomonas aeruginosa is not well documented. In this study, laboratory batch studies were conducted to assess the effect of a variety of factors, e.g., carbon sources, salinity, initial Cr(VI) concentrations, co-existing ions and a metabolic inhibitor, on microbial Cr(VI) reduction to Cr(III) by P. aeruginosa AB93066. Strain AB93066 tolerated up to 400 mg/L of Cr(VI) in nutrient broth medium compared to only 150 mg/L of Cr(VI) in nutrient agar. This bacteria exhibited different levels of resistance against Pb(II) (200 mg/L), Cd(II) (100 mg/L), Ni(II) (100 mg/L), Cu(II) (100 mg/L), Co(II) (50 mg/L) and Hg(II) (5 mg/L). Cr(VI) reduction was significantly promoted by the addition of glucose and glycerine but was strongly inhibited by the presence of methanol and phenol. The rate of Cr(VI) reduction increased with increasing concentrations of Cr(VI) and then decreased at higher concentrations. The presence of Ni(II) stimulated Cr(VI) reduction, while Pb(II), Co(II) and Cd(II) had adverse impact on reduction ability of this strain. Cr(VI) reduction was also inhibited by high levels of NaCl, various concentrations of sodium azide and 20 mM of SO₄ ^2?, MoO₄ ^2?, NO₃ ^?, PO₄ ^3?. No significant relationship was observed between Cr(VI) reduction and redox potential of the culture medium. Scanning electron microscopy showed visible morphological changes in the cells due to chromate stress. Fourier transform infrared spectroscopy analysis revealed chromium species was likely to form complexes with certain functional groups such as carboxyl and amino groups on the surface of P. aeruginosa AB93066. Overall, above results are beneficial to the bioremediation of chromate-polluted industrial wastewaters.     

Bioreduction of hexavalent chromium by <Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis> L1 and <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> L2

Bioreduction of the very toxic hexavalent chromium ion [Cr(VI)] to the non-toxic trivalent chromium ion [Cr(III)] is a key remediation process in chromium-contaminated sites. In this study, we investigated the bioreduction of Cr(VI) by Pseudomonas stutzeri L1 and Acinetobacter baumannii L2. The optimum pH (5–10), temperature (27, 37 and 60 °C) and initial chromium Cr(VI) concentration (100–1000 mg L^?1) for Cr(VI) reduction by strains L1 and L2 were determined using the diphenylcarbazide method. In the presence of L1 and L2, the bioreduction rate of Cr(VI) was 40–97 and 84–99%, respectively. The bioreduction of Cr(VI) by L2 was higher, reaching up to 84%—than that by L1. The results showed that strain L2 was able to survive even if exposed to 1000 mg L^?1 of Cr(VI) and that this tolerance to the effects of Cr(VI) was linked to the activity of soluble enzyme fractions. Overall, A. baumannii L2 would appear to be a potent Cr(VI)-tolerant candidate for the bioremediation of chromium (VI)-contaminated wastewater effluent.     

Soil chromium bioremediation: Synergic activity of actinobacteria and plants

The aim of this work was to evaluate a strategy to reduce the bioavailable chromium fraction in soil, using a Cr(VI) resistant microorganism, Streptomyces sp. MC1, under non sterile conditions, with maize plants as bioindicator and/or bioremediator.Soil samples were contaminated with 100, 200 and 400 mg kg⁻¹ of Cr(VI) or Cr(III). Bioavailable chromium (35%) was only detected in samples with Cr(VI). Soil samples with Cr(VI) 200 mg kg⁻¹ were inoculated with Streptomyces sp. MC1, and bioavailable chromium decreased up to 73%.Zea mays seedlings were planted in soil samples contaminated with chromium. Plantlets accumulated chromium mainly as Cr(III), and biomass decreased up to 88%. Streptomyces sp. MC1 was inoculated in soil samples contaminated with 200 mg kg⁻¹ of Cr(VI) and Z.mays seedlings were planted.Streptomyces sp. MC1 caused Z.mays biomass increase (57%), chromium accumulation and bioavailable chromium decreased up to 46% and 96%, respectively.This work constitutes the first contribution of cooperative action between actinobacteria and Z.mays in the bioremediation of Cr(VI) contaminated soil. The large removal capacity of bioavailable chromium by Streptomyces sp. MC1 and Z.mays infers that they could be successfully applied together in bioremediation of soils contaminated with Cr(VI).