Mycodegradation of low-density polyethylene by Cladosporium sphaerospermum, isolated from platisphere

Plastic accumulation is a severe threat to the environment due to its resistivity to thermal, mechanical and biological processes. In recent years, microbial degradation of plastic waste disposal is of interest because of its eco-friendly nature. In this study, a total of 33 fungi were isolated from the plastisphere and out of which 28 fungal species showed halo zone of clearance in agarized LDPE media. The fungus showing highest zone of clearance was further used to evaluate its degradation potential. Based on morphological and molecular technique, the fungus was identified as Cladosporium sphaerospermum. The biodegradation of LDPE by C. sphaerospermum was evaluated by various methods. The exposure of LDPE with C. sphaerospermum resulted in weight loss (15.23%) in seven days, higher reduction rate (0.0224/day) and lower half-life (30.93 days). FTIR analysis showed changes in functional group and increased carbonyl index in LDPE treated with C. sphaerospermum. SEMimages evidenced the formation of pits, surface aberrations and grooves on the LDPE film treated with the fungus whereas the untreated control LDPE film showed no change. AFM analysis confirmed the surface changes and roughness in fungus treated LDPE film. This might be due to the extracellular lignolytic enzymes secreted by C. sphaerospermum grown on LDPE. The degradation of polyethylene by Short chain alkanes such as dodecane, hexasiloxane and silane were identified in the extract of fungus incubated with LDPE film through GC-MS analysis which might be due to the degradation of LDPE film by C. sphaerospermum. This was the first report on the LDPE degradation by C. sphaerospermum in very short duration which enables green scavenging of plastic wastes.

Comparitive Study of Reamed vs Unreamed Interlocking Intra Medullary Nailing for Fracture Shaft of Tibia

Tibia is the commonest bone to sustain open injury because of subcutaneous position. Treatment of open fractures requires simultaneous management of both skeletal and soft tissue injury. Intramedullary nailing with reaming is generally considered to be contraindicated for open fractures tibia, because it damages the endosteal blood supply which will lead to non-union, deep infection. However, recent studies with or without reaming in open fracture tibia shows no influence in healing of fracture. Purpose: To compare the clinical and radiological results of intramedullary interlocking nailing of open fractures of the tibial shaft after reaming versus unreamed medullary canal. The aim and objective is a comparative study on the technique, outcome and time taken for clinical and radiological union in either of the reamed or unreamed interlocking nailing in tibial shaft fractures. The operative technique, advantages and disadvantages, follow up, time taken for bony and radiological union and complications if any and overall functional outcome will be evaluated in patients. The follow up of patients will be done in the immediate post operative period and  subsequently  at periodic intervals both clinically and radiologically and the result so obtained will be compared.

Substituent enhanced fluorescence properties of star α-cyanostilbenes and their application in bioimaging

In this paper, we report the fluorescence properties of new star α-cyanostilbene molecules. Fungus cell imaging studies using one of the molecules allowed observing nuclear movement in the live mycelium.

Secretion of keratinolytic enzymes and keratinolysis by Scopulariopsis brevicaulis and Trichophyton mentagrophytes: regression analysis

A survey on keratinophilic fungi from poultry-farm soils at Namakkal and from feather dumping soils at Chennai, India, revealed the existence of 34 species of fungi. Most of the fungi exhibited variable efficiency in producing extracellular keratinase when grown in plates with chicken feathers as the sole carbon and nitrogen source. The fungi Aspergillus flavus, Aspergillus niger, Aspergillus versicolor, Chrysosporium state of Arthroderma tuberculatum, Paecilomyces carneus, Scopulariopsis brevicaulis, Trichoderma viride, and Trichophyton mentagrophytes were efficient candidates to degrade the feathers. However, when cultivating the strains in submerged conditions in a medium containing chicken feathers as the sole nutrients source, Aspergillus glaucus, Chrysosporium keratinophilum, Curvularia lunata, Fusarium solani, and Penicillium citrinum also proved to be potent. Among all species, S. brevicaulis and Trichophyton mentagrophytes produced higher amounts of keratinase in both methods. Conditions for keratinase production were optimized by statistical design and surface plots. The highest keratinase activity was estimated by S. brevicaulis (3.2 KU/mL) and Trichophyton mentagrophytes (2.7 KU/mL) in the culture medium with chicken feathers and shows (79% and 72.2% of degrading ability, respectively).

Self-fusion of protoplasts enhances chitinase production and biocontrol activity in Trichoderma harzianum

Protoplasts were isolated from Trichoderma harzianum strain PTh18 using lysing enzymes and self-fusion of T. harzianum protoplasts was carried out using polyethylene glycol in STC buffer. The fused protoplasts of T. harzianum were regenerated and 15 self-fusants were selected to study the chitinase production and biocontrol activity. High chitinase activity was measured in the culture filtrates of most of the self-fusants (87%) than the parent. Among the fusants, the strain SFTh8 produced maximum chitinase with a two-fold increase as compared to the parent strain. All the self-fusants exhibited increased antagonistic activity against Rhizoctonia solani than the parent. The crude chitinase preparation of SFTh8 lysed the mycelia of T. harzianum, Trichoderma viride and Trichoderma reesei and released the protoplasts in higher number than the crude chitinase preparation of parent strain PTh18.

Improvement of physical stability and dissolution rate of celecoxib suspensions by complexation with beta-cyclodextrins

Solid dispersions of celecoxib with beta-cyclodextrins were prepared by physical mixing, slugging and kneading methods at 1:1 and 1:2 molar ratios and characterized by differential scanning calorimetry. Celecoxib suspensions were formulated employing its solid dispersions with sodium carboxymethylcellulose as the suspending agent. Stability studies were conducted by subjecting all the suspensions to freeze-thaw cycling. The suspensions were evaluated for particle size, sedimentation volume, viscosity, redispersibility and dissolution rate initially and after stability testing. Celecoxib suspensions formulated employing its solid dispersions exhibited good physical stability and gave higher dissolution rates than those formulated with celecoxib alone. The suspension prepared from solid dispersions (1:2) by the kneading method gave the highest improvement in dissolution rate and efficiency. Celecoxib in the inclusion complex with beta-cyclodextrin produced suspensions of better physical stability and dissolution rate.

Nanosuspensions as the most promising approach in nanoparticulate drug delivery systems

Over the years, controlled drug delivery as well as site-specific delivery have made considerable advances. One area that contributed significantly to this progress is the rapidly developing field of colloidal drug delivery systems. Nanoparticles, one of the colloidal drug delivery systems, may enable new possibilities for therapy that presently have not been investigated. Recent advances in nanoparticle research are discussed here. The present review highlights new and upcoming developments such as nanosuspensions and solid lipid nanoparticles.

Purification, characterization, and antifungal activity of chitinase from Fusarium chlamydosporum, a mycoparasiteto groundnut rust, Puccinia arachidis

Chitinase (EC 3.2.1.14) was isolated from the culture filtrate of Fusarium chlamydosporum and purified by ion-exchange chromatography and gel filtration. The molecular mass of purified chitinase was 40 kDa as estimated by sodium dodecyl sulfate – polyacrylamide gel electrophoresis. Chitinase was optimally active at a pH of 5 and stable from pH 4 to 6 and up to 40°C. Among the metals and inhibitors tested, mercuric chloride completely inhibited the enzyme activity. The activity of chitinase was high on colloidal and pure chitin. The purified chitinase inhibited the germination of uredospores of Puccinia arachidis and also lysed the walls of uredospores and germ tubes. The results from these experiments indicated that chitinase of F. chlamydosporum plays an important role in the biocontrol of groundnut rust. Key words: Fusarium chlamydosporum, chitinase, purification, Puccinia arachidis, uredospores.

Purification, characterization, and antifungal activity of chitinase from Fusarium chlamydosporum, a mycoparasite to groundnut rust, Puccinia arachidis

Chitinase (EC 3.2.1.14) was isolated from the culture filtrate of Fusarium chlamydosporum and purified by ion-exchange chromatography and gel filtration. The molecular mass of purified chitinase was 40 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Chitinase was optimally active at a pH of 5 and stable from pH 4 to 6 and up to 40 degrees C. Among the metals and inhibitors tested, mercuric chloride completely inhibited the enzyme activity. The activity of chitinase was high on colloidal and pure chitin. The purified chitinase inhibited the germination of uredospores of Puccinia arachidis and also lysed the walls of uredospores and germ tubes. The results from these experiments indicated that chitinase of F. chlamydosporum plays an important role in the biocontrol of groundnut rust.

Generation and spectroscopic and kinetic characterization of methoxy-substituted phenoxyl radicals in solution and on paper

A number of methoxy-substituted phenoxyl radicals have been generated and characterized by laser flash photolysis techniques in solution and on paper. The radicals have been produced by three routes in solution: hydrogen abstraction from phenols by tert-butoxyl radical, photolysis of α-aryloxyacetophenones, and direct excitation of phenols. Most of the phenoxyl radicals studied have a characteristic absorption near 400 nm; the ortho-substituted radicals have an additional broad absorption in the visible in non-hydroxylic solvents (e.g., 650 nm for 2-methoxyphenoxyl radical). The relative intensities of the 400 nm and the long-wavelength bands vary with substitution pattern and solvent, with the long wavelength band being much weaker in hydroxylic solvents. Direct excitation of phenols provides an alternate source of phenoxyl radicals in some cases. However, for 4-methoxyphenol there are overlapping absorptions due to triplet phenol and phenol radical cation, both of which absorb in the 400–460 nm region. The 4-methoxyphenol radical cation is formed in a biphotonic process and decays by deprotonation to give the phenoxyl radical. The 4-methoxyphenoxyl radical can also be generated on paper from either the ketone or phenol precursor and decays with complex kinetics that depend on the precursor loading and laser intensity. There is no evidence for the formation of significant amounts of long-lived ketone or phenol triplets on paper. The decay kinetics for the phenoxyl radical are modified by the addition of the radical scavenger dithioerythritol. The results indicate both static and dynamic components to the radical scavenging process. The generation of phenoxyl radicals on paper in the presence and absence of scavengers provides the basis for the development of a new method for screening potential photoyellowing inhibitors and understanding their mode of action. Keywords: phenoxyl radicals, paper photoyellowing, laser flash photolysis, triplets, radical cations.

Assignment and vibrational analysis of the 600 nm absorption band in the phenoxyl radical and some of its derivatives

An experimental and theoretical study is reported of the 600 nm band system of phenoxyl and several methoxy substituted phenoxyls. These radicals, generated in freon, show a diffuse band in this region with a vibrational structure that is incompletely resolved but consistent with the 500 cm−1 "progression" observed earlier for phenoxyl in the vapour and in a rigid matrix. The low intensity of this band is considerably enhanced by ortho-methoxy substitution. To establish its assignment and analyze its structure, semi-empirical and ab initio quantum chemical calculations have been performed. It is found that, on the basis of the ordering of the states and the magnitude of their transition moments, all calculations favour a ππ* (2B2 → 2A2) rather than the earlier proposed nπ* assignment for this band. Of the methods used, only the (ab initio) CASSCF method is found to be able to simulate the observed vibrational structure adequately. This simulation is based on optimized structures and vibrational force fields calculated for the 1B2 and 1A2 states of phenoxyl. It identifies the dominant mode of about 500 cm−1 as ν6a the characteristic deformation mode of phenyl rings, but shows that higher members of the "progression" receive large intensity contributions from higher frequency modes. The chosen assignment and the assignments of higher-energy transitions reported in the literature are compared with those for the better known benzyl radical. It is shown that some of the phenoxyl assignments reported in the literature contain errors.

Photochemistry of lignin model compounds on solid supports

The photochemistry of several substituted α-(aryloxy)acetoveratrones that are models for chromophores in lignin has been studied using a combination of laser flash photolysis and product studies in solution and on silica, Na-X zeolite, and cellulose. The lifetimes of the triplet ketones vary substantially with the electron-donating ability of the substituents in the α-aryloxy ring, with values ranging from 30 ns for the 4-methoxy derivative to 5.5 µs for the 4-cyano ketone in acetonitrile. The triplet ketones are considerably longer lived on a silica surface than in solution and do not decay with first-order kinetics; however, they are all shorter lived than triplet acetoveratrone under the same conditions, indicating that β-phenyl quenching and (or) β-cleavage dominate their decay. The same triplets show quite different kinetic behavior in Na-X or cellulose and there is no indication in these systems for the importance of either β-phenyl quenching or β-cleavage in determining the rates of triplet decay. Product studies for α-guaiacoxyacetoveratrone indicate that β-cleavage from the singlet excited state is responsible for product formation; in contrast to solution results, the phenacyl–phenoxyl radical pairs react exclusively by geminate recombination to give rearranged ketones resulting from ortho and para ring coupling of the two radicals. Product formation is very inefficient for this ketone in cellulose, indicating either a low singlet reactivity or efficient geminate recombination of the initial radical pair to regenerate starting material.

Kinetics of breakdown of aryl hemiacetals of α-bromoacetophenone. Effect of phenol leaving groups on the lifetimes of tetrahedral intermediates

The kinetics of breakdown of seven aryl hemiacetals of α-bromoacetophenone (TOH) have been examined, with aryl substituents 4-MeO, 4-Me, 3-Me, H, 3-MeO, 4-Cl, 3-Cl. The hemiacetals were generated as intermediates in the aqueous bromination of α-aryloxystyrenes, where the breakdown of the hemiacetal is the rate-limiting stage in the overall reaction. Base catalysis of the breakdown shows large Brønsted β values (0.8–1.0) and similarly large βlg values (−0.8 to −1.0). These are argued to arise because of a preassociation mechanism in which the hydrogen-bonded intermediate [Formula: see text] loses aryloxide faster than diffusional separation of the acid–base pair. This mechanism is enforced by lifetimes of the deprotonated hemiacetals TO− in the 1010–1012 s−1 range. Such lifetimes were estimated in two independent ways, by extrapolation of data previously obtained for alkyl hemiacetals of α-bromoacetophenone, and through a calculation based upon the experimental catalytic coefficients, and estimates of the acidity constants for TOH and the equilibrium constants for formation of hydrogen-bonded complexes. The pH-independent breakdown has βlg = −1.03, and the point lies near the Brønsted line for the carboxylate catalysts. This, therefore, also occurs by a preassociation mechanism with water as the catalyst forming the intermediate [Formula: see text], which loses aryloxide faster than diffusional separation. Catalysis by hydroxide ion occurs with rate constants of 8 × 109 M−1 s−1 independent of aryl substituent. This represents rate-limiting diffusional encounter of the hemiacetal and hydroxide ion, the hydrogen-bonded intermediate [Formula: see text] rapidly proceeding on to products. Acid catalysis of the hemiacetal breakdown occurs by a class "n" mechanism in which the acid assists departure of the substitued phenol. Alkyl hemiacetals of α-bromoacetophenone break down by a class "e" mechanism where the leaving group is fully protonated before bond cleavage. The class "e" mechanism can be excluded for the aryl derivatives, since rate constants much greater then diffusion are required to explain the observed catalytic coefficients. The different mechanism is followed in order to avoid the fully protonated hemiacetal, which, being of an O-protonated anisole structure, is of very high energy. Key words: hemiacetal kinetics, preassociation, intermediate lifetime.