Optimized culture conditions for bacterial cellulose production by Acetobacter senegalensis MA1

Background

Cellulose, the most versatile biomolecule on earth, is available in large quantities from plants. However, cellulose in plants is accompanied by other polymers like hemicellulose, lignin, and pectin. On the other hand, pure cellulose can be produced by some microorganisms, with the most active producer being Acetobacter xylinum. A. senengalensis is a gram-negative, obligate aerobic, motile coccus, isolated from Mango fruits in Senegal, capable of utilizing a variety of sugars and produce cellulose. Besides, the production is also influenced by other culture conditions. Previously, we isolated and identified A. senengalensis MA1, and characterized the bacterial cellulose (BC) produced.

Results

The maximum cellulose production by A. senengalensis MA1 was pre-optimized for different parameters like carbon, nitrogen, precursor, polymer additive, pH, temperature, inoculum concentration, and incubation time. Further, the pre-optimized parameters were pooled, and the best combination was analyzed by using Central Composite Design (CCD) of Response Surface Methodology (RSM). Maximum BC production was achieved with glycerol, yeast extract, and PEG 6000 as the best carbon and nitrogen sources, and polymer additive, respectively, at 4.5 pH and an incubation temperature of 33.5 °C. Around 20% of inoculum concentration gave a high yield after 30 days of inoculation. The interactions between culture conditions optimized by CCD included alterations in the composition of the HS medium with 50 mL L^− 1 of glycerol, 7.50 g L^− 1 of yeast extract at pH 6.0 by incubating at a temperature of 33.5 °C along with 7.76 g L^− 1 of PEG 6000. This gave a BC yield of wet weight as 469.83 g L^− 1.

Conclusion

The optimized conditions of growth medium resulted in enhanced production of bacterial cellulose by A. senegalensis MA1, which is around 20 times higher than that produced using an unoptimized HS medium. Further, the cellulose produced can be used in food and pharmaceuticals, for producing high-quality paper, wound dressing material, and nanocomposite films for food packaging.

EPR and IR spectral investigations on some leafy vegetables of Indian origin

EPR spectral investigations have been carried out on four edible leafy vegetables of India, which are used as dietary component in day to day life. In Rumex vesicarius leaf sample, EPR spectral investigations at different temperatures indicate the presence of anti-ferromagnetically coupled Mn(IV)-Mn(IV) complexes. EPR spectra of Trigonella foenum graecum show the presence of Mn ions in multivalent state and Fe(3+) ions in rhombic symmetry. EPR spectra of Basella rubra indicate the presence of Mn(IV)-O-Mn(IV) type complexes. The EPR spectra of Basella rubra have been studied at different temperatures. It is found that the spin population for the resonance signal at g=2.06 obeys the Boltzmann distribution law. The EPR spectra of Moringa oliefera leaves show the presence of Mn(2+) ions. Radiation induced changes in free radical of this sample have also been studied. The FT-IR spectra of Basella rubra and Moringa oliefera leaves show the evidences for the protein matrix bands and those corresponding to carboxylic CO bonds.

EPR as an analytical tool in assessing the mineral nutrients and irradiated food products-vegetables

EPR spectral investigations of some commonly available vegetables in south India, which are of global importance like Daucus carota (carrot), Cyamopsis tetragonoloba (cluster beans), Coccinia indica (little gourd) and Beta vulgaris (beet root) have been carried out. In all the vegetable samples a free radical corresponding to cellulose radical is observed. Almost all the samples under investigation exhibit Mn ions in different oxidation states. The temperature variation EPR studies are done and are discussed in view of the paramagnetic oxidation states. The radiation-induced defects have also been assessed by using the EPR spectra of such irradiated food products.

Method and quantity of liquid formulation of phosphobacteria required for seed inoculation

The survival of vegetative and sporulated cells of the Bacillus cultures on the seeds of the crop plants was tried in different combinations. One milliliter inoculum with 1 mL adhesive combination or sterile water showed better results followed by 1.5 mL inoculum with 0.5 mL adhesive or sterile water. The population of 5.5x10(5) cfu seed(-1) on black gram, 10.5x10(5) cfu seed(-1) on soybean and 6.5x10(5) cfu seed(-1) on maize were observed after 12 h of incubation in 1 mL sporulated inoculum mixed with 1 mL of rice gruel. The sporulated inoculum along with rice gruel favoured the adherence of the regenerated cells as rice gruel is rich in nutrient content.

Low Temperature Kinetics and Energetics of the Electron and Hole Traps in Irradiated TiO2 Nanoparticles as Revealed by EPR Spectroscopy

We have monitored exclusively the dynamics of photogenerated charge carriers trapping in deep traps and trapped electron-hole recombination in UV irradiated anatase TiO2 powders by electron paramagnetic resonance (EPR) spectroscopy at 10 K. The results reveal that the strategy of using low temperatures contributes to the stabilization of the charged pair states for hours by reducing the rate of electron-hole recombination processes. Since only the localized states such as holes trapped at oxygen anions and electrons trapped at coordinatively unsaturated cations are accessible to EPR spectroscopy, the time-dependent population and depopulation of these EPR signals reflect the kinetics and energetics of these trap states. The data support a model of sequential accumulation of deep trap site populations in which the initial fast direct trapping into a deep trap site is followed by slower carrier trap-to-trap hopping until a deep trap is encountered for both photogenerated electrons and holes. Effective modeling of the subsequent decay of trapped-holes is achieved by employing a first-order kinetics, whereas the decay of either surface- or inner-trapped electrons has both a fast and a slow component. The fast component is attributed to a trapped-electron and a free-hole recombination, and the slow component is attributed to trapped electron-hole recombination. The activation energies for the process of diffusion of trapped electrons from their Ti3+ trapping sites are estimated.

EPR and optical investigations of manganese ions in alkali lead tetraborate glasses

Electron paramagnetic resonance (EPR) and optical absorption spectra of Mn2+ ions in different alkali lead tetraborate glasses 90R2B4O7+9.25PbO+0.75MnSO4 (R=Li, Na and K) and 90Li2B4O7+(10-x)PbO+xMnSO4 (x=0.1, 0.25, 0.5, 0.75, 1.0, 1.25, 1.5 and 2 mol%) have been studied. The EPR spectrum of all the glass samples exhibit three resonance signals at g=2.0, 3.3 and 4.3. The resonance signal at g=2.0 is attributed to the Mn2+ ions in an environment close to an octahedral symmetry. The resonance signals at g=3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn2+ ions. The effect of temperature (123-433 K) and the composition dependence of EPR signals have been studied for Mn2+ ions in lithium lead tetraborate glasses. It is interesting to observe that the variation of paramagnetic susceptibility (chi) with temperature obeys Curie-Weiss law. From the slope of 1/chi versus T graph, the Curie constant (C) has been evaluated. The zero-field splitting (zfs) parameter D has been calculated for different alkali lead tetraborate glasses from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits three bands. An intense and broad band at lower energy side has been assigned to the spin-allowed (5Eg-->5T2g) transition of Mn3+ ions in an octahedral symmetry. The intense and sharp band and a broad band at higher energy side have been assigned to charge transfer bands. A red shift is observed with increase of alkali ion size. The optical band gap energy (Eopt) decreases, whereas the Urbach energies (DeltaE) increases with increase of Mn content. The theoretical values of optical basicity (Lambdath) of the glasses have also been evaluated.

Fe(3+) ions in alkali lead tetraborate glasses--an electron paramagnetic resonance and optical study

Glass systems of composition 90R(2)B(4)O(7)+9PbO+1Fe(2)O(3) (R=Li, Na and K) and 90Li(2)B(4)O(7)+(10-x)PbO+xFe(2)O(3) (x=0.5, 1, 3, 4, 5, 7 and 9 mol %) have been investigated by means of electron paramagnetic resonance (EPR) and optical absorption techniques. The EPR spectra exhibit three resonance signals at g approximately 6.0, 4.2 and 2.0. The resonances at g approximately 6.0 and 4.2 are attributed to Fe(3+) ions in rhombic and axial symmetry sites, respectively. The g approximately 2.0 resonance signal is due to two or more Fe(3+) ions coupled together with dipolar interaction. The EPR spectra of 1 mol % of Fe(2)O(3) doped in lithium lead tetraborate glass samples have been studied at different temperatures (123-433 K). The intensity of g approximately 4.2 resonance signal decreases and the intensity of g approximately 2.0 resonance signal increases with the increase of temperature. The line widths are found to be independent of temperature. The EPR spectra exhibit a marked concentration dependence on iron content. A decrease in intensity for the resonance signal at g approximately 4.2 with increase in iron content for more than 4 mol % has been observed in lithium lead tetraborate glass samples and this has been attributed to the formation of Fe(3+) ion clusters in the glass samples. The paramagnetic susceptibility (chi) is calculated from the EPR data at various temperatures and the Curie constant (C) has been evaluated from 1/chi versus T graph. The optical absorption spectrum of Fe(3+) ions in lithium lead tetraborate glasses exhibits three bands characteristic of Fe(3+) ions in an octahedral symmetry. The crystal field parameter D(q) and the Racah interelectronic repulsion parameters B and C have also been evaluated. The value of interelectronic repulsion parameter B (825 cm(-1)) obtained in the present work suggests that the bonding is moderately covalent.

EPR and optical absorption studies on Cr3+ ions doped in KZnClSO4 x 3H2O single crystals

EPR and optical absorption spectra of Cr3+ ions doped in KZnClSO4 x 3H2O single crystals have been studied at room temperature. The EPR spectrum exhibits a group of three fine structure transitions characteristic of Cr3+ ions. From the observed EPR spectra, the spin-Hamiltonian parameters have been determined. The optical absorption spectrum exhibits two broad bands characteristic of Cr3+ ions in an octahedral symmetry. From the observed band positions, the crystal field parameters have been evaluated.

EPR, optical and infrared absorption studies of Mn2+ ions doped in zinc malate trihydrate single crystal

Electron paramagnetic resonance (EPR) studies have been carried out on Mn2+ ions doped in zinc malate trihydrate single crystals in the temperature range 123-413 K on X-band frequency. The EPR spectrum at room temperature exhibits a group of five fine structure transitions each splits into six hyperfine components. Angular variation studies reveal that Mn2+ ions enter the lattice substitutionally. From the observed EPR spectrum, the spin-Hamiltonian parameters have been evaluated. The variation of zero-field splitting parameter (D) with temperature is measured. From the optical absorption spectrum, the crystal field splitting parameter Dq and the Racah interelectronic repulsion parameters B and C have been evaluated. The infrared spectrum exhibits bands characteristic of the carboxylic acid salts.

Structural studies of the biomineralized species of calcified pancreatic stones in patients suffering from chronic pancreatitis

The pancreatic stones (Pancreatic calculi) collected from patients suffering from chronic calcific pancreatitis were studied in a view to explore the constituents involved in the calcification. The calcified stones were characterized by XRD, EPR and IR spectroscopic techniques. The detailed studies indicate that these stones consist of calcium carbonate as a major component, besides phosphates and other protein content. The presence of aragonite phases in the biomineralized stones is also discussed. The EPR spectra gave an evidence of the presence of traces of manganese in different oxidation states, which is used as one of the EPR probes in the present work. The samples were sintered at different temperatures to remove all the organic matter, and their EPR spectra have been studied to obtain detailed information regarding the changes in the symmetry of these stone samples. The X-irradiated sample was also characterized by EPR and the resonance signals are attributed to freely rotating CO(2)(-) radicals. The infrared spectrum reveals the presence of many organic bands corresponding to the protein amides.

EPR, optical, infrared and Raman spectral studies of Actinolite mineral

Electron paramagnetic resonance (EPR), optical, infrared and Raman spectral studies have been performed on a natural Actinolite mineral. The room temperature EPR spectrum reveals the presence of Mn(2+) and Fe(3+) ions giving rise to two resonance signals at g = 2.0 and 4.3, respectively. The resonance signal at g = 2.0 exhibits a six line hyperfine structure characteristic of Mn(2+) ions. EPR spectra have been studied at different temperatures from 123 to 433 K. The number of spins (N) participating in the resonance at g = 2.0 has been calculated at different temperatures. A linear relationship is observed between log N and 1/T in accordance with Boltzmann law and the activation energy was calculated. The paramagnetic susceptibility (chi) has been calculated at different temperatures and is found to be increasing with decreasing temperature as expected from Curie's law. From the graph of 1/chi versus T, the Curie constant and Curie temperature have been evaluated. The optical absorption spectrum exhibits bands characteristic of Fe(2+) and Fe(3+) ions. The crystal field parameter Dq and the Racah parameters B and C have been evaluated from the optical absorption spectrum. The infrared spectral studies reveal the formation of Fe(3+)--OH complexes due to the presence of higher amount of iron in this mineral. The Raman spectrum exhibits bands characteristic of Si--O--Si stretching and Mg?OH translation modes.

The microstructures of biomineralized surfaces: a spectroscopic study on the exoskeletons of fresh water (Apple) snail, Pila globosa

In view of the importance in understanding biomineralization processes in different molluskan species, the common fresh water apple snail Pila globosa in Indian origin was taken to explore its mineralized exoskeleton structures. The detailed structural studies of the exoskeletons of P. globosa have been undertaken. The isolated layers present in these shells were studied by electron paramagnetic resonance (EPR), optical absorption, and infrared spectral techniques. The EPR spectra of the organic protein layer periostracum show the characteristic signals corresponding to Fe(3+) ions at g = 4.1 and 2.0. The EPR spectra of the ostracum (middle) layer at room temperature gives a complicated spectrum consisting of a number of Mn(2+) signals of at least three sets due to the aragonite nature of the material. The results indicate the presence of the multivalent manganese ions, which undergo the redox mechanisms. The thermal variation of the EPR spectra show marked effect on these samples both in g-values and the basic spectral pattern.

Structural studies of marine exoskeletons: redox mechanisms observed in the Cu-supported CaCO3 surfaces tudied by EPR

Electron Paramagnetic Resonance (EPR), optical and infrared (IR) spectral studies have been performed on the pure and Cu-adsorbed exoskeletons of marine environment. The EPR spectrum of exoskeletons at room temperature exhibits a sharp signal at g approximately 1.9970. The possible redox mechanisms have been noticed on heating these exoskeletons in which the low spin Mn(3+) reduces to Mn(2+). The optical absorption spectra also give the evidence of the presence of Mn(3+) ions. The effects of thermal sintering on the EPR spectra have been studied and discussed in detail. The Cu-adsorbed samples clearly showed the adsorption of the Cu(2+) ions over CaCO(3) and the redox mechanism in these samples have been monitored by EPR.