Sudha Yadava

Azadirachta indica plant-assisted green synthesis of Mn3O4 nanoparticles: Excellent thermal catalytic performance and chemical sensing behavior.

The leaf extract of Azadirachta indica (Neem) plant was utilized as reducing agent for the green synthesis of Mn3O4 nanoparticles (NPs). The crystalline analysis demonstrated the typical tetragonal hausmannite crystal structure of Mn3O4, which confirmed the formation of Mn3O4 NPs without the existence of other oxides. Green synthesized Mn3O4 NPs were applied for the catalytic thermal decomposition of ammonium perchlorate (AP) and as working electrode for fabricating the chemical sensor. The excellent catalytic effect for the thermal decomposition of AP was observed by decreasing the decomposition temperature by 175 °C with single decomposing step. The fabricated chemical sensor based on green synthesized Mn3O4 NPs displayed high, reliable and reproducible sensitivity of ∼569.2 μA mM(-1) cm(-2) with reasonable limit of detection (LOD) of ∼22.1 μM and the response time of ∼10 s toward the detection of 2-butanone chemical. A relatively good linearity in the ranging from ∼20 to 160 μM was detected for Mn3O4 NPs electrode based 2-butanone chemical sensor.

Syntheses of Aromatic Aldehydes by Laccase of Pleurotus ostreatus MTCC-1801

Abstract Selective bioconversion of the aromatic methyl group to its aldehyde group is one of the best applications of the laccases. In the present communication, crude laccase, obtained from the liquid culture medium of the fungal strain Pleurotus ostreatus MTCC-1801, has been used for the selective bioconversion of toluene, 3-nitrotoluene, 4-nitrotoluene, 2-fluorotoluene, 4-fluorotoluene, 2-chlorotoluene, 3-chlorotoluene, 4-chlorotoluene, and 3,4-dimethoxytoluene to benzaldehyde, 3-nitrobenzaldehyde, 4-nitrobenzaldehyde, 2-fluorobenzaldehyde, 4-fluorobenzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-chlorobenzaldehyde, and 3,4-dimethoxybenzaldehyde, respectively, in the presence of 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) as a mediator molecule. Time taken by these conversions was 1–2 h, and average yield of products was more than 93%. GRAPHICAL ABSTRACT

Purification and characterization of laccase secreted by Phellinus linteus MTCC-1175 and its role in the selective oxidation of aromatic methyl group

A laccase from the culture filtrate of Phellinus linteus MTCC-1175 has been purified to homogeneity. The method involved concentration of the culture filtrate by ammonium sulphate precipitation and an anion exchange chromatography on DEAE-cellulose. The SDS-PAGE and native-PAGE gave single protein band indicating that the enzyme preparation was pure. The molecular mass of the enzyme determined from SDS-PAGE analysis was 70 kDa. Using 2.6-dimethoxyphenol, 2.2′[azino-bis-(3-ethylbonzthiazoline-6-sulphonic acid) diammonium salt] (ABTS) and 4-hydroxy-3,5-dimethoxybenzaldehyde azine as the substrates, the Km, kcat and kcat/Km values of the laccase were found to be 160 μM, 6.85 s−1, 4.28 × 104 M−1 s−1, 42 μM, 6.85 s−1, 16.3 × 104 M−1 s−1 and 92 μM, 6.85 s−1, 7.44 × 104 M−1 s−1, respectively. The pH and the temperature optima of the P. linteus MTCC-1175 laccase were 5.0 and 45°C, respectively. The activation energy for thermal denaturation of the enzyme was 38.20 kJ/mole/K. The enzyme was the most stable at pH 5.0 after 1 h reaction. In the presence of ABTS as the mediator, the enzyme transformed toluene, 3-nitrotoluene and 4-chlorotoluene to benzaldehyde, 3-nitrobenzaldehyde and 4-chlorobenzaldehyde, respectively.

α-l-rhamnosidase selective for rutin to isoquercitrin transformation from Penicillium griseoroseum MTCC-9224

An α-l-rhamnosidase secreting fungal strain has been isolated from the decaying goose berry (Emblica officinalis) fruit peel. The fungal strain has been identified as Penicillium greoroseum MTCC-9224. The α-l-rhamnosidase of this fungal strain has been purified to homogeneity using a simple procedure involving concentration by ultra filtration and an anion exchange chromatography on DEAE-cellulose. The purified enzyme gave a single protein band corresponding to molecular mass of 97kDa in SDS-PAGE analysis. The native-PAGE analysis also gave a single protein band confirming the purity of the enzyme. Using p-nitrophenyl-α-l-rhamnopyranoside as the substrate, Km and kcat values of the enzyme were 0.65mM and 43.65s-1, respectively. The pH and temperature optima of the enzyme were 6.5 and 57°C, respectively. The activation energy for the thermal denaturation of the enzyme was 27.9kJ/mol. The purified α-l-rhamnosidase hydrolyzed rutin to isoquercitrin and l-rhamnose but has no effect on naringin and hesperidin.

Selective oxidation and N-coupling by purified laccase of Xylaria polymorpha MTCC-1100

The chemical route of oxidation of methyl group to its aldehyde is inconvenient because once a methyl group is attacked, it is likely to be oxidized to the carboxylic acid and it is very difficult to stop the reaction at the aldehyde stage. Fungal laccases can be used for such oxidation reaction and the reaction can be completed sharply within 1–2 h. Coupling of amines are another important reactions known for fungal laccases; coupling reactions generally take 3–7 h. We have used the purified laccase of molecular weight 63 kDa obtained from the fungal strain Xylaria polymorpha MTCC-1100 with activity of 1.95 IU/mL for selective oxidation of 2-fluorotoluene, 4-fluorotoluene, and 2-chlorotoluene to 2-fluorobenzaldehyde, 4-fluorobenzaldehyde, and 2-chlorobenzaldehyde, respectively, and syntheses of 3-(3, 4-dihydroxyphenyl)-propionic acid derivatives by N-coupling of amines. In each oxidation reactions, ABTS was used as mediator molecule. All the syntheses are ecofriendly and were performed at room temperature.

Syntheses of aromatic aldehydes by laccase without the help of mediators

This communication reports the selective bioconversions of substituted toluenes to substituted benzaldehydes without the help of any mediators by purified laccase of indigenous fungal strain Fomes durissimus microbial type culture collection (MTCC)-1173. Molecular mass of laccase purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was found to be 74.86 kDa (∼75 kDa). By using this purified laccase, selective bioconversions of 3-nitrotoluene to 3-nitrobenzaldehyde, 2-fluorotoluene to 2-fluorobenzaldehyde, 4-fluorotoluene to 4-fluorobenzaldehyde, 2-chlorotoluene to 2-chlorobenzaldehyde and 4-chlorotoluene to 4-chlorobenzaldehyde have been done without the help of mediator molecules within 1–2 hrs at room temperature and pressure with high yields (>90%). All the above bioconversions are good examples of green chemistry.

Purification, characterisation and coal depolymerisation activity of lignin peroxidase from Lenzitus betulina MTCC-1183

Lignin peroxidase from the culture filtrate of Lenzitus betulina MTCC-1183 has been purified to homogeneity using concentration by ultrafiltration and anion exchange chromatography on DEAE cellulose. The molecular weight of the purified lignin peroxidase using SDS-PAGE analysis was 43 kDa. Specific activity of the enzyme was 29.58 IU/mg. The Km values for veratryl alcohol and H2O2 for the purified enzyme were 54 and 81 μM, respectively. The kcat value of the purified enzyme was 2.3 s−1 using 3,4-dimethoxybenzyl alcohol as the substrate. The optimal conditions for the lignin peroxidase assay were detected at pH 2.4 and 22°C. Thermal stability of the purified enzyme has also been studied and its activation energy for deactivation was 287 kJ/mol. The purified lignin peroxidase depolymerised humic acid in presence of H2O2. Depolymerisation of coal by the L. betulina MTCC-1183 has been demonstrated using humic acid as a model of coal.

Novel complexes of Mn(III) with macrocylic porphine ligand and ethylenediamine

The present work describes the synthesis and characterization of a few Mn(III) porphyrins with ethylenediamine. A new series of high-spin Mn(III) porphyrins having general formula [Mn(TMPP)X] and [Mn(TMPP)X(en)], where TMPP = tetra-p-methoxyphenylporphinato ligand, X = Cl−, Br−, or NCS− and en = ethylenediamine. Molar conductance values of these complexes show their non-electrolytes in ethyl alcohol. These complexes have been characterized by U.V., I.R., ESI-mass spectra, elemental analyses and magnetic susceptibility measurements. The tentative structures have also been proposed.

Synthetic applications of purified laccase from Pleurotus sajor caju MTCC-141

The study is devoted to the role of laccase, purified from the liquid culture medium of the indigenous fungal strain Pleurotus sajor caju MTCC-141, in selective bioconversion of toluene derivatives into substituted benzaldehydes with high yield. Coupling reactions of 3-(3,4-dihydroxyphenyl)propionic acid with 4-aminobenzoic, 4-aminoacetophenone and 1-hexylamine proceeded at room temperature under the action of laccase to give the corresponding products with excellent yields.

Amination of p-hydroquinone by laccase of Xylaria polymorpha MTCC-1100

The communication is devoted to the study of activity of crude laccase obtained from the liquid culture growth media of fungal strain Xylaria polymorpha MTCC-1100 in coupling processes of aromatic amines with p-hydroquinone. Products of monoamination were obtained under mild condition with high yields.