Self-immobilization of Recombinant Caulobacter crescentus and Its Application in Removal of Cadmium from Water

Microbial biofilms can be valuable in many biotechnological applications, including bioremediation. We have previously constructed a recombinant strain of Caulobacter crescentus JS4022/p723-6H by inserting a hexahistidine peptide to a permissive site of the host surface layer (S-layer) protein RsaA. This engineered strain is highly effective in removal of cadmium from water as free cells. In this communication, we examined the biofilms formed by self-immobilized JS4022/p723-6H and evaluated their ability to retrieve cadmium from contaminated water samples. According to light and electron microscopic observations, JS4022/p723-6H cells developed a uniform monolayer biofilm on borosilicate surfaces through their intrinsic appendage, a stalk with an adhesive holdfast. The density of the biofilms reached a maximum after 48 h of incubation and was not affected by exposure to at least 1 ppm cadmium. When 0.4 ppm Cd(II) was added to the growth medium, immobilized JS4022/p723-6H removed 76.9% of the total metal, whereas the control strain only removed 13.5%. When a water sample collected from Lake Erie was spiked with various amounts of CdCl₂, immobilized JS4022/p723-6H was able to sequester 44～51% of the total metal, compared to 37～42% accumulated by the control strain. By combining two powerful techniques, cell surface display and self-immobilization, we achieved complete separation of dissolved heavy metals from contaminated water in a single step. This study laid down the foundation to cost-effectively construct large-scale bioreactors with high efficiency and specificity to retrieve environmental contaminants from water.     

Synthesis and Biological Evaluation of Novel Chalcone and Pyrazoline Derivatives Bearing Substituted Vanillin Nucleus

A series of novel chalcone 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l and pyrazoline 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l derivatives have been synthesized as potential antibacterial agents. The pyrazoline derivatives 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l have been synthesized by reaction of various chalcones 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l with hydrazine hydrate in the presence of acetic acid. The chalcones 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l were prepared by the condensation of key aldehyde 3 with appropriate acetophenone using basic condition and ethanol as a solvent. The key aldehyde 3 has been synthesized by reacting 2‐(chloromethyl)‐3‐methyl‐4‐(2,2,2‐trifluoroethoxy)pyridine hydrochloride and vanillin. The structures of the new compounds were established on the basis of ¹H‐NMR, mass, IR, and elemental analysis data. All the newly synthesized compounds were screened for their antibacterial activity against Escherichia coli, Salmonella typhi (Gram‐negative bacteria), Staphylococcus aureus, Micrococcus luteus (Gram‐positive bacteria) and antifungal activity against Candida albicans (fungi).     

X‐ray Absorption Near‐Edge Structure and Nuclear Magnetic Resonance Study of the Lithium–Sulfur Battery and its Components

Understanding the mechanism(s) of polysulfide formation and knowledge about the interactions of sulfur and polysulfides with a host matrix and electrolyte are essential for the development of long‐cycle‐life lithium–sulfur (Li–S) batteries. To achieve this goal, new analytical tools need to be developed. Herein, sulfur K‐edge X‐ray absorption near‐edge structure (XANES) and ^6,7Li magic‐angle spinning (MAS) NMR studies on a Li–S battery and its sulfur components are reported. The characterization of different stoichiometric mixtures of sulfur and lithium compounds (polysulfides), synthesized through a chemical route with all‐sulfur‐based components in the Li–S battery (sulfur and electrolyte), enables the understanding of changes in the batteries measured in postmortem mode and in operando mode. A detailed XANES analysis is performed on different battery components (cathode composite and separator). The relative amounts of each sulfur compound in the cathode and separator are determined precisely, according to the linear combination fit of the XANES spectra, by using reference compounds. Complementary information about the lithium species within the cathode are obtained by using ⁷Li MAS NMR spectroscopy. The setup for the in operando XANES measurements can be viewed as a valuable analytical tool that can aid the understanding of the sulfur environment in Li–S batteries.     

Phytochemical composition,antioxidant activity and HPLC profiles of Swertia species from Western Ghats

Swertia chirayita is one of the potential medicinal plants of the family Gentianaceae in traditional medicine. Due to its high demand and scarcity, trade of chirayita is affected by adulterants. Swertia species from Western Ghats were compared with S. chirayita for phytochemical characterisation and antioxidant activities by using different extracts. This study revealed that acetone is the best extraction solvent of phenolic and flavonoid compounds with antioxidant properties as compared with other extracts. S. chirayita showed better antioxidant activity than other species with highest content of phenolics and flavonoids. Among the species from Western Ghats, Swertia minor has better antioxidant properties with higher content of phenolics and flavonoids when compared with S. chirayita. Gallic acid was detected in all species under study by using HPLC analysis. The Swertia species under study showed similar phytochemical properties and antioxidant potential and hence their use as substitute to S. chirayita needs to be further investigated.     

Activity-guided investigation of Carissa carandas (L.) roots for anti-inflammatory constituents

The present study was structured to investigate the anti-inflammatory potential of the extracts, fractions and compounds isolated from Carissa carandas (L.) roots. Bioassay guided fractionation of methanol extract based on inhibitory potential towards proinflammatory mediators (TNF-α, IL-1β and nitric oxide (NO)) led to the identification of stigmasterol (1), lupeol (2), oleanolic acid (3), carissone (4) and scopoletin (5) as potential anti-inflammatory agents. Carissone (4) (IC₅₀ = 20.1 ± 2.69 μg/mL) and scopoletin (5) (IC₅₀ = 24.6 ± 1.36 μg/mL) exhibited significant inhibition of NO production comparable to specific NO inhibitor (L-NAME; IC₅₀ = 19.82 ± 1.64 μg/mL) without affecting the cell viability. Also, 4 and 5 at a concentration of 30 μM were found to inhibit 41.88–53.44% of TNF-α and IL-1β. To the best of our knowledge, this is the first report displaying the anti-inflammatory effects of C. carandas (L.) roots, partially mediated by inhibition of TNF-α, IL-1β and NO.     

Quality‐by‐design‐based ultra high performance liquid chromatography related substances method development by establishing the proficient design space for sumatriptan and naproxen combination

Quality‐by‐design‐based methods hold greater level of confidence for variations and greater success in method transfer. A quality‐by‐design‐based ultra high performance liquid chromatography method was developed for the simultaneous assay of sumatriptan and naproxen along with their related substances. The first screening was performed by fractional factorial design comprising 44 experiments for reversed‐phase stationary phases, pH, and organic modifiers. The results of screening design experiments suggested phenyl hexyl column and acetonitrile were the best combination. The method was further optimized for flow rate, temperature, and gradient time by experimental design of 20 experiments and the knowledge space was generated for effect of variable on response (number of peaks ≥ 1.50 – resolution). Proficient design space was generated from knowledge space by applying Monte Carlo simulation to successfully integrate quantitative robustness metrics during optimization stage itself. The final method provided the robust performance which was verified and validated. Final conditions comprised Waters® Acquity phenyl hexyl column with gradient elution using ammonium acetate (pH 4.12, 0.02 M) buffer and acetonitrile at 0.355 mL/min flow rate and 30°C. The developed method separates all 13 analytes within a 15 min run time with fewer experiments compared to the traditional quality‐by‐testing approach.     

Ethanol extracts of Hemidesmus indicus leaves as eco-friendly inhibitor of mild steel corrosion in H2SO4 medium

The inhibitory action of an extract of Hemidesmus indicus leaves as a potential corrosion inhibitor for steel in H₂SO₄ solutions was examined using conventional mass loss, gasometric techniques, electrochemical polarisations and electrochemical impedance spectroscopy. The results revealed that the extract of Hemidesmus indicus leaves performed well as an inhibitor for the corrosion of the metal employed in an accelerating medium. The inhibition efficiencies for all the experimental techniques employed increased with increasing the concentration of the plant extract but decreased with a rise in temperature. Both the cathodic hydrogen evolution and the anodic dissolution of mild steel were inhibited, hence the active molecule of the extract studied acted as a mixed-type corrosion inhibitor.