Hexavalent Chromium Reduction and Accumulation by <Emphasis Type="Italic">Acinetobacter</Emphasis> AB1 Isolated from Fez Tanneries in Morocco

Hexavalent chromium reduction and accumulation by Acinetobacter AB1 isolated from Fez tanneries effluents were tested. The effects of some environmental factors such as pH, temperature, and exposure time on Cr(VI) reduction and resistance were investigated. We found that this strain was able to resist to concentrations as high as 400 mg/l of Cr(VI). Moreover, pH 10 and the temperature 30°C constitute favourable conditions to the growth and reduction of Acinetobacter AB1. Complete reduction of Cr(VI) was observed at low initial Cr(VI) concentrations of 50 mg/l after 72 h of incubation. Furthermore, Transmission electron microscope (TEM) analysis showed morphological changes in AB1 strain due 48H exposure to 100 mg/l chromate concentration and revealed circular electron dense (dark black point) inclusion within the cell cytoplasm suggesting chromium deposition within the cells.     

Treatment of Alkaline Cr(VI)-Contaminated Leachate with an Alkaliphilic Metal-Reducing Bacterium

Chromium in its toxic Cr(VI) valence state is a common contaminant particularly associated with alkaline environments. A well-publicized case of this occurred in Glasgow, United Kingdom, where poorly controlled disposal of a cementitious industrial by-product, chromite ore processing residue (COPR), has resulted in extensive contamination by Cr(VI)-contaminated alkaline leachates. In the search for viable bioremediation treatments for Cr(VI), a variety of bacteria that are capable of reduction of the toxic and highly soluble Cr(VI) to the relatively nontoxic and less mobile Cr(III) oxidation state, predominantly under circumneutral pH conditions, have been isolated. Recently, however, alkaliphilic bacteria that have the potential to reduce Cr(VI) under alkaline conditions have been identified. This study focuses on the application of a metal-reducing bacterium to the remediation of alkaline Cr(VI)-contaminated leachates from COPR. This bacterium, belonging to the Halomonas genus, was found to exhibit growth concomitant to Cr(VI) reduction under alkaline conditions (pH 10). Bacterial cells were able to rapidly remove high concentrations of aqueous Cr(VI) (2.5 mM) under anaerobic conditions, up to a starting pH of 11. Cr(VI) reduction rates were controlled by pH, with slower removal observed at pH 11, compared to pH 10, while no removal was observed at pH 12. The reduction of aqueous Cr(VI) resulted in the precipitation of Cr(III) biominerals, which were characterized using transmission electron microscopy and energy-dispersive X-ray analysis (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The effectiveness of this haloalkaliphilic bacterium for Cr(VI) reduction at high pH suggests potential for its use as an in situ treatment of COPR and other alkaline Cr(VI)-contaminated environments.     

Fe(III), Cr(VI), and Fe(III) mediated Cr(VI) reduction in alkaline media using a <Emphasis Type="Italic">Halomonas</Emphasis> isolate from Soap Lake,Washington

Hexavalent chromium is one of the most widely distributed environmental contaminants. Given the carcinogenic and mutagenic consequences of Cr(VI) exposure, the release of Cr(VI) into the environment has long been a major concern. While many reports of microbial Cr(VI) reduction are in circulation, very few have demonstrated Cr(VI) reduction under alkaline conditions. Since Cr(VI) exhibits higher mobility in alkaline soils relative to pH neutral soils, and since Cr contamination of alkaline soils is associated with a number of industrial activities, microbial Cr(VI) reduction under alkaline conditions requires attention. Soda lakes are the most stable alkaline environments on earth, and contain a wide diversity of alkaliphilic organisms. In this study, a bacterial isolate belonging to the Halomonas genus was obtained from Soap Lake, a chemically stratified alkaline lake located in central Washington State. The ability of this isolate to reduce Cr(VI) and Fe(III) was assessed under alkaline (pH = 9), anoxic, non-growth conditions with acetate as an electron donor. Metal reduction rates were quantified using Monod kinetics. In addition, Cr(VI) reduction experiments were carried out in the presence of Fe(III) to evaluate the possible enhancement of Cr(VI) reduction rates through electron shuttling mechanisms. While Fe(III) reduction rates were slow compared to previously reported rates, Cr(VI) reduction rates fell within range of previously reported rates.     

In vitro evaluation of new functional properties of poly-γ-glutamic acid produced by Bacillus subtilis D7

We investigated the functionality of poly-γ-glutamic acid (γ-PGA), which is produced by Bacillus subtilis D7, for its potential applications in medicine and cosmetics. The γ-PGA had angiotensin-converting enzyme (ACE) inhibition activity. ACE inhibition activity was dependent on the γ-PGA concentration; the highest ACE inhibition activity was observed at 1.25 mg/l of γ-PGA. IC₅₀ (0.108 mg/ml) of the γ-PGA was lower than that of standard ACE inhibitory drug, N-[(S)-mercapto-2-methylpropionyl]-L-proline (0.247 mg/ml). The γ-PGA also had water-holding capacity and hygroscopicity. Furthermore, the γ-PGA inhibited growth of some pathogenic bacteria, including Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, Klebsiella pneumonia and Esherichia coli. The γ-PGA exhibited a good metal adsorption capacity; Cr (VI) adsorption capacity of γ-PGA increased with decreasing pH, and the maximal adsorption was observed at pH 2. Our results suggest that γ-PGA may be expected to be widely applied in cosmetics, biomedical and environmental industries with the feature of being less harmful to humans and the environment.     

Alkaline Anaerobic Respiration: Isolation and Characterization of a Novel Alkaliphilic and Metal-Reducing Bacterium

Iron-reducing enrichments were obtained from leachate ponds at the U.S. Borax Company in Boron, Calif. Based on partial small-subunit (SSU) rRNA gene sequences (approximately 500 nucleotides), six isolates shared 98.9% nucleotide identity. As a representative, the isolate QYMF was selected for further analysis. QYMF could be grown with Fe(III)-citrate, Fe(III)-EDTA, Co(III)-EDTA, or Cr(VI) as electron acceptors, and yeast extract and lactate could serve as electron donors. Growth during iron reduction occurred over the pH range of 7.5 to 11.0 (optimum, pH 9.5), a sodium chloride range of 0 to 80 g/liter (optimum, 20 g/liter), and a temperature range of 4 to 45°C (optimum, approximately 35°C), and iron precipitates were formed. QYMF was a strict anaerobe that could be grown in the presence of borax, and the cells were straight rods that produced endospores. Sodium chloride and yeast extract stimulated growth. Phylogenetic analysis of the SSU rRNA gene indicated that the bacterium was a low-G+C gram-positive microorganism and had 96 and 92% nucleotide identity with Alkaliphilus transvaalensis and Alkaliphilus crotonatoxidans, respectively. The major phospholipid fatty acids were 14:1, 16:1ω7c, and 16:0, which were different from those of other alkaliphiles but similar to those of reported iron-reducing bacteria. The results demonstrated that the isolate might represent a novel metal-reducing alkaliphilic species. The name Alkaliphilus metalliredigens sp. nov. is proposed. The isolation and activity of metal-reducing bacteria from borax-contaminated leachate ponds suggest that bioremediation of metal-contaminated alkaline environments may be feasible and have implications for alkaline anaerobic respiration.     

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.     

Escherichia coli NemA Is an Efficient Chromate Reductase That Can Be Biologically Immobilized to Provide a Cell Free System for Remediation of Hexavalent Chromium

Hexavalent chromium is a serious and widespread environmental pollutant. Although many bacteria have been identified that can transform highly water-soluble and toxic Cr(VI) to insoluble and relatively non-toxic Cr(III), bacterial bioremediation of Cr(VI) pollution is limited by a number of issues, in particular chromium toxicity to the remediating cells. To address this we sought to develop an immobilized enzymatic system for Cr(VI) remediation. To identify novel Cr(VI) reductase enzymes we first screened cell extracts from an Escherichia coli library of soluble oxidoreductases derived from a range of bacteria, but found that a number of these enzymes can reduce Cr(VI) indirectly, via redox intermediates present in the crude extracts. Instead, activity assays for 15 candidate enzymes purified as His6-tagged proteins identified E. coli NemA as a highly efficient Cr(VI) reductase (k_cat/K_M  = 1.1×10⁵ M⁻¹s⁻¹ with NADH as cofactor). Fusion of nemA to the polyhydroxyalkanoate synthase gene phaC from Ralstonia eutropha enabled high-level biosynthesis of functionalized polyhydroxyalkanoate granules displaying stable and active NemA on their surface. When these granules were combined with either Bacillus subtilis glucose dehydrogenase or Candida boidinii formate dehydrogenase as a cofactor regenerating partner, high levels of chromate transformation were observed with only low initial concentrations of expensive NADH cofactor being required, the overall reaction being powered by consumption of the cheap sacrificial substrates glucose or formic acid, respectively. This system therefore offers promise as an economic solution for ex situ Cr(VI) remediation.     

Purification to Homogeneity and Characterization of a Novel Pseudomonas putida Chromate Reductase

Cr(VI) (chromate) is a widespread environmental contaminant. Bacterial chromate reductases can convert soluble and toxic chromate to the insoluble and less toxic Cr(III). Bioremediation can therefore be effective in removing chromate from the environment, especially if the bacterial propensity for such removal is enhanced by genetic and biochemical engineering. To clone the chromate reductase-encoding gene, we purified to homogeneity (>600-fold purification) and characterized a novel soluble chromate reductase from Pseudomonas putida, using ammonium sulfate precipitation (55 to 70%), anion-exchange chromatography (DEAE Sepharose CL-6B), chromatofocusing (Polybuffer exchanger 94), and gel filtration (Superose 12 HR 10/30). The enzyme activity was dependent on NADH or NADPH; the temperature and pH optima for chromate reduction were 80°C and 5, respectively; and the K_m was 374 μM, with a V_max of 1.72 μmol/min/mg of protein. Sulfate inhibited the enzyme activity noncompetitively. The reductase activity remained virtually unaltered after 30 min of exposure to 50°C; even exposure to higher temperatures did not immediately inactivate the enzyme. X-ray absorption near-edge-structure spectra showed quantitative conversion of chromate to Cr(III) during the enzyme reaction.     

Hexavalent chromium reduction by bacterial consortia and pure strains from an alkaline industrial effluent

Aims: To characterize the bacterial consortia and isolates selected for their role in hexavalent chromium removal by adsorption and reduction. Methods and Results: Bacterial consortia from industrial wastes revealed significant Cr(VI) removal after 15 days when incubated in medium M9 at pH 6·5 and 8·0. The results suggested chromium reduction. The bacterial consortia diversity (T‐RFLP based on 16S rRNA gene) indicated a highest number of operational taxonomic units in an alkaline carbonate medium mimicking in situ conditions. However, incubations under such conditions revealed low Cr(VI) removal. Genomic libraries were obtained for the consortia exhibiting optimal Cr(VI) removal (M9 medium at pH 6·5 and 8·0). They revealed the dominance of 16S rRNA gene sequences related to the genera Pseudomonas/Stenotrophomonas or Enterobacter/Halomonas, respectively. Isolates related to Pseudomonas fluorescens and Enterobacter aerogenes were efficient in Cr(VI) reduction and adsorption to the biomass. Conclusions: Cr(VI) reduction was better at neutral pH rather than under in situ conditions (alkaline pH with carbonate). Isolated strains exhibited significant capacity for Cr(VI) reduction and adsorption. Significance and Impact of Study: Bacterial communities from chromium‐contaminated industrial wastes as well as isolates were able to remove Cr(VI). The results suggest a good potential for bioremediation of industrial wastes when optimal conditions are applied.     

Reduction of hexavalent chromium by Pseudomonas fluorescens LB300 in batch and continuous cultures

Batch and continuous cultures of Pseudomonas fluorescens LB300 were shown to reduce hexavalent chromium, Cr(VI), aerobically at neutral pH (pH 7.0) with citrate as carbon and energy source. The product of Cr(VI) reduction was previously shown and confirmed in this work to be trivalent chromium, Cr(III), by quantitative reoxidation to Cr(VI) with KMnO₄. In separate batch cultures (100 ml) containing initial Cr(VI) concentrations of 314.0, 200.0 and 112.5 mg Cr(VI) L^–1, the organism reduced 61%, 69% and 99.7% of the Cr(VI), respectively. In a comparison of stationary and shaken cultures, the organism reduced 81% of Cr(VI) in 147 h in stationary culture and 80% in 122 h in shaken culture. In continuous culture, the organism lowered the influent Cr(VI) concentration by 28% with an 11.7-h residence time, by 39% with a 20.8-h residence time and by 57% with a 38.5-h residence time. A mass balance of chromium in a continuous culture at steady state showed an insignificant uptake of chromium by cells of P. fluorescens LB300. Correspondence to: P. C. DeLeo     

Flavonoid constituents,cytotoxic and antioxidant activities of Gleditsia triacanthos L. leaves

Gleditsia triacanthos L. is a deciduous tree belonging to the family Fabaceae. It possesses important biological activities as anti-mutagenic, anticancer, cytotoxic and treating rheumatoid arthritis. The total ethanol extract (EtOHE) and successive extracts (petroleum ether, chloroform, ethyl acetate, and aqueous ethanol) were prepared from the leaves. Eight flavone glycosides and two flavone aglycones named vicenin-I (1), vitexin (2), isovitexin (3), orientin (4), isoorientin (5), luteolin-7-O-ß-glucopyranoside (6), luteolin-7-O-ß-galactopyranoside (7), apigenin-7-O-ß-glucopyranoside (8), luteolin (9) and apigenin (10) were isolated from the aqueous ethanol extract of G. triacanthos L. leaves. Potent cytotoxic activity of the EtOHE extract was observed against the liver (IC₅₀ = 1.68 μg), breast (IC₅₀ = 0.74 μg), cervix (IC₅₀ = 1.28 μg), larynx (IC₅₀ = 0.67 μg) and colon (IC₅₀ = 2.50 μg) cancer cell lines. Cytotoxic activity of compounds 2, 4, 6 and 8 against, the liver, breast and colon cancer cell lines was also proved. Evaluation of the in-vivo antioxidant activity of the EtOHE and successive extracts revealed that the highest activity was exhibited by 100 mg of EtOHE (97.89% potency) as compared with vitamin E (100% potency). Compound 6 showed 91.8% free radical scavenging activity.     

Investigations of anticholinestrase and antioxidant potentials of methanolic extract,subsequent fractions,crude saponins and flavonoids isolated from Isodon rugosus

Background

Based on the ethnomedicinal uses and the effective outcomes of natural products in various diseases, this study was designed to evaluate Isodon rugosus as possible remedy in oxidative stress, alzheimer’s and other neurodegenerative diseases. Acetylecholinestrase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of crude methanolic extract (Ir.Cr), resultant fractions (n-hexane (Ir.Hex), chloroform (Ir.Cf), ethyl acetate (Ir.EtAc), aqueous (Ir.Aq)), flavonoids (Ir.Flv) and crude saponins (Ir.Sp) of I. rugosus were investigated using Ellman’s spectrophotometric method. Antioxidant potential of I. rugosus was determined using DPPH, H₂O₂ and ABTS free radicals scavenging assays. Total phenolic and flavonoids contents of plant extracts were determined and expressed in mg GAE/g dry weight and mg RTE/g of dry sample respectively.

Results

Among different fractions Ir.Flv and Ir.Cf exhibited highest inhibitory activity against AChE (87.44 ± 0.51, 83.73 ± 0.64%) and BChE (82.53 ± 0.71, 88.55 ± 0.77%) enzymes at 1 mg/ml with IC₅₀ values of 45, 50 for AChE and 40, 70 μg/ml for BChE respectively. Activity of these fractions were comparable to galanthamine causing 96.00 ± 0.30 and 88.61 ± 0.43% inhibition of AChE and BChE at 1 mg/ml concentration with IC₅₀ values of 20 and 47 μg/ml respectively. In antioxidant assays, Ir.Flv, Ir.Cf, and Ir.EtAc demonstrated highest radicals scavenging activities in DPPH and H₂O₂ assays which were comparable to ascorbic acid. Ir.Flv was found most potent with IC₅₀ of 19 and 24 μg/ml against DPPH and H₂O₂ radicals respectively. Whereas antioxidant activates of plant samples against ABTS free radicals was moderate. Ir.Cf, Ir.EtAc and Ir.Cr showed high phenolic and flavonoid contents and concentrations of these compounds in different fractions correlated well to their antioxidant and anticholinestrase activities.

Conclusion

It may be inferred from the current investigations that the Ir.Sp, Ir.Flv and various fractions of I. rugosus are good sources of anticholinesterase and antioxidant compounds. Different fractions can be subjected to activity guided isolation of bioactive compounds effective in neurological disorders.     

Biochemical characterization of Santalum album (Chandan) leaf peroxidase

The Santalum peroxidase was extracted from the leaves and precipitated with double volume of chilled acetone. The optimum percent relative activity for the Santalum peroxidase was observed at pH 5.0 and 50 °C temperature. The Santalum peroxidase per cent relative activity was stimulated in the presence of phenolic compounds like ferrulic acid and caffeic acids; however, indole-3-acetic acid (IAA) and protocatechuic acid act as inhibitors. All divalent cations Fe²⁺, Mn²⁺, Mg²⁺, Cu²⁺ and Zn²⁺ stimulate the relative activity of the Santalum peroxidase at concentration of 2.0 μM. Amino acids like L-alanine and L-valine activate the per cent relative activity, while L-proline and DL-methionine showed moderate inhibition for the Santalum peroxidase. However, a very low a concentration of cysteine acts as a strong inhibitor of Santalum peroxidase at the concentration of 0.4 mM. Native polyacrylamide gel electrophoresis (Native-PAGE) was performed for isoenzyme determination and two bands were observed. K_m and V_max values were calculated from Lineweaver-Burk graph. The apparent V_max/K_m value for O-dianisidine and H₂O₂ were 400 and 5.0 × 105 Units/min/mL respectively.     

Effects of Riyadh cement industry pollutions on some physiological and morphological factors of Datura innoxia Mill. plant

Cement factory emissions into air cause serious air pollution and affect the plant and animal life in the environment. Herein, we report the effects of cement industry emissions (O₃, SO₂ and NO₂) in air, as pollutants, at Riyadh City on Datura innoxia Mill. plant. Morphological characters including plant height, leaves area and number, fresh and dry weight of shoot and root systems of D. innoxia showed a significant reduction from their normal control plants as a response to exposure to pollutant emissions. Chlorophyll and carotenoid contents recorded reductions in values compared to control plant, and the lowest values of chlorophyll A, B, total chlorophyll, carotenoids and total pigments were 0.431, 0.169, 0.60, 0.343 and 0.943 mg/g respectively at a distance of 1–5 m from the cement factory in fruiting stage. These changes in values may be attributed to a probable deceleration of the biosynthetic process rather than degradation of pigments. Further D. innoxia showed a significant (P < 0.01) reduction in non-reducing and total sugars, protein and total lipid contents compared with the control plant. The root system recorded the lowest values of reducing sugars (0.350 mg/g f. wt.), non-reducing sugars (0.116 mg/g f. wt.), total sugars (0.466 mg/g f. wt.), protein content (0.931 mg/g f. wt.) and total lipids content (0.669 mg/g f. wt.) in fruiting stage at a distance of 1–5 m from the cement factory. The peroxidase activity of shoot and root systems of the studied plant was also significantly higher than those of control plant. Thus a highest value of (29.616 units/g f. wt.) peroxidase activity was recorded in vegetative stage of shoot system at a distance 1–5 m from the cement factory. Results of the study indicated that cement industry emission strongly influence the physiology and morphology of date palm D. innoxia which contribute date fruits, a staple food in the Arab world.     

Hepatoprotective effect of Rhodiola imbricata rhizome against paracetamol-induced liver toxicity in rats

Rhodiola imbricata is a perennial herb of the family Crassulaceae, which has significant traditional usage as medicine and is also known to biosynthesize phytochemicals such as flavonoids, coumarins and phenyl glycosides. The present investigation was aimed to estimate the hepatoprotective activity of R. imbricata rhizome acetone extract against paracetamol (2 g/kg) induced liver toxicity. Paracetamol was administered to induce hepatic damage in Wistar rats. 200 and 400 mg/kg doses of rhizome acetone extract and silymarin (25 mg/kg) were used as treatment groups. The blood samples were analyzed for biochemical markers of hepatic injury and tissue samples were subjected for estimation of liver antioxidants and histopathological studies. Analysis of the extract treated rats (400 mg/kg) showed an elevation of superoxide dismutase (0.326 units/min/mg protein), catalase (185.03 μmole of H₂O₂ consumed/min/mg protein), glutothione peroxidase (19.26 mg GSH consumed/min/mg protein) and reduced glutathione (16.2 μmole of GSH/mg protein). Moreover, the biochemical parameters in serum like alkaline phosphatase, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT) and lipid profiles were also improved in treated groups compared to the control. The oral administration of different doses of rhizome acetone extract significantly protected the hepatic cells from damage. The hematological and biochemical parameters were also normal in extract treated rats compared to the control and standard (silymarin) groups. The HPLC analysis revealed the presence of some important phenolic compounds which could be responsible for the hepatoprotective activity. This study proved that R. imbricata could be taken as a good natural source of the hepatoprotective agent.     

Simultaneous Cr(VI) reduction and phenol degradation in pure cultures of Pseudomonas aeruginosa CCTCC AB91095

Simultaneous Cr(VI) reduction and phenol degradation were investigated in a reactor containing Pseudomonas aeruginosa CCTCC AB91095. Phenol was used as carbon source. P.aeruginosa utilized metabolites formed during phenol degradation as energy source for Cr(VI) reduction. Cr(VI) inhibited both Cr(VI) reduction and phenol degradation when Cr(VI) concentration exceeded the optimum value (20 mg/L), whereas phenol enhanced both Cr(VI) reduction and phenol degradation below the optimum initial concentration of 100 mg/L. Cr(III) was the predominant product of Cr(VI) reduction in cultures after incubation for 24 h. Both Cr(VI) reduction and phenol degradation were influenced by the amount of inocula. The concentration of Cr(VI) and phenol declined quickly from 20, 100 to 3.36, 29.51 mg/L in cultures containing of 5% (v/v) inoculum after incubation for 12 h, respectively. The whole study showed that P. aeruginosa is promising for the reduction of toxic Cr(VI) and degradation of organic pollutants simultaneously in the mineral liquid medium.     

Optimization of Fermentation Conditions and Properties of an Exopolysaccharide from Klebsiella sp. H-207 and Application in Adsorption of Hexavalent Chromium

The novel exopolysaccharide HZ-7 is produced by Klebsiella sp. H-207, and its fermentation conditions were optimized by response surface methodology (RSM). In this study, the optimized medium consisted of sucrose 31.93 g/L, KNO₃ 2.17 g/L and K₂HPO₄ 5.47 g/L; while the optimized culture conditions consisted of seed age 13 h, with an inoculum size of 10.6% and incubation temperature of 28.9°C. A maximum HZ-7 yield of about 15.05 g/L was achieved under the optimized conditions using RSM and single-factor experiments. Next the exopolysaccharide HZ-7 was partially purified and characterized. The resulting product showed good properties, such as high concentration of uronic acid (41.67%), low average molecular weight (about 1.94×10⁵ Da) and porous surface structure, were very advantageous to biosorption. Therefore HZ-7 was applied to absorb hexavalent chromium (Cr(VI)). The maximum adsorption efficiency (99.2%) which was obtained at an initial pH of 1.0 along with an initial Cr(VI) concentration of 20 mg/L, was not affected by ordinary metal ions and temperature. These data suggest Klebsiella sp. H-207 exopolysaccharide will be promising potential for industrial application.     

Thermus parvatiensis RLT sp. nov., Isolated from a Hot Water Spring,Located Atop the Himalayan Ranges at Manikaran,India

A Gram negative, yellow pigmented, rod shaped bacterium designated as RL^T was isolated from a hot water spring (90–98 °C) located at Manikaran in Northern India. The isolate grows at 60–80 °C (optimum, 70 °C) and at pH 7.0–9.0 (optimum pH 7.2). Phylogenetic analysis of 16S rRNA gene sequences and levels of DNA–DNA relatedness together indicate that the new isolate represents a novel species of the genus Thermus with closest affinity to Thermus thermophilus HB8^T (99.5 %) followed by Thermus arciformis (96.4 %). A comparative analysis of partial sequences of housekeeping genes (HKG) further revealed that strain RL^T is a novel species belonging to the genus Thermus. The melting G+C content of strain RL^T was calculated as 68.7 mol%. The DNA–DNA relatedness value of strain RL^T with its nearest neighbours (>97 %) was found to be less than 70 % indicating that strain RL^T represents a novel species of the genus Thermus. MK-8 was the predominant respiratory quinone. The presence of characteristic phospholipid and glycolipid further confirmed that strain RL^T belongs to the genus Thermus. The predominant fatty acids of strain RL^T were iso-C_17:0 (23.67 %) and iso-C_15:0 (24.50 %). The results obtained after DNA–DNA hybridization, biochemical and physiological tests clearly distinguished strain RL^T from its closely related species. Thus, strain RL^T represents a novel species of the genus Thermus for which the name Thermus parvatiensis is proposed (=DSM 21745^T= MTCC 8932^T).

Electronic supplementary material

The online version of this article (doi:10.1007/s12088-015-0538-4) contains supplementary material, which is available to authorized users.     

De-hairing protease production by an isolated Bacillus cereus strain AT under solid-state fermentation using cow dung: Biosynthesis and properties

Agro-industrial residues and cow dung were used as the substrate for the production of alkaline protease by Bacillus cereus strain AT. The bacterial strain Bacillus cereus strain AT produced a high level of protease using cow dung substrate (4813 ± 62 U g⁻¹). Physiological fermentation factors such as the incubation time (72 h), the pH (9), the moisture content (120%), and the inoculum level (6%) played a vital role in the enzyme bioprocess. The enzyme production improved with the supplementation of maltose and yeast extract as carbon and nitrogen sources, respectively. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis and zymogram analysis of the purified protease indicated an estimated molecular mass of 46 kDa. The protease enzyme was stable over a temperature range of 40–50 °C and pH 6–9, with maximum activity at 50 °C and pH 8. Among the divalent ions tested, Ca²⁺, Na⁺ and Mg²⁺ showed activities of 107 ± 0.7%, 103.5 ± 1.3%, and 104.6 ± 0.9, respectively. The enzyme showed stability in the presence of surfactants such as sodium dodecyl sulfate and on various commercially available detergents. The crude enzyme effectively de-haired goat hides within 18 h of incubation at 30 °C. The enzymatic properties of this protease suggest its suitable application as an additive in detergent formulation and also in leather processing. Based on the laboratory results, the use of cow dung for producing and extracting enzyme is not cumbersome and is easy to scale up. Considering its cheap cost and availability, cow dung is an ideal substrate for enzyme bioprocess in an industrial point of view.     

Chromium stress induced oxidative burst in Vigna mungo (L.) Hepper: physio-molecular and antioxidative enzymes regulation in cellular homeostasis

Vigna mungo (L.) Hepper commonly known as blackgram is an important legume crop with good quality dietary proteins and vitamins. Low production of blackgram in the chromium rich soil of Odisha is a serious concern against its demand. Chromium (VI) was tested on V. mungo var. B3-8-8 at 100, 150, 200, 250 and 300 µM concentration on growth, anti-oxidative enzymes and chromium content at 15, 30 and 45 d of treatments. Seed germination and growth decreased with increase dose and duration. Cr uptake induced oxidative burst with significant increase of osmolytes was observed in cell at lower doses but failed to adjust homeostasis at higher dose. Increase of GPX and SOD and decrease of CAT was observed as dose dependent. Increased protein content was detected in < 200 µM Cr concentration whereas, significant decrease of protein was noted thereafter. Down regulation of proteins (29.2 kDa and 32.6 kDa) was observed at > 250 µM of Cr. Total Cr uptake was greater in root than in shoot which might be due to poor translocation of heavy metal or detoxification. Thus, blackgram was able to maintain homeostasis at lower concentrations of Cr by activating the cascade of enzymes following cellular detoxification mechanism.Supplementary InformationThe online version of this article contains supplementary material available at (10.1007/s12298-021-00941-3)