Development of a mathematical model for Bacillus circulans growth and alkaline protease production kinetics

BACKGROUND: An unstructured mathematical model was developed to understand information on the relationship between Bacillus circulans growth and metabolism‐related protease production (using logistic and Luedeking–Piret equations respectively) in a batch reactor with respect to glucose consumption and fermentation time. The objective was to develop an indispensable tool for the optimisation, control, design and analysis of alkaline protease production. RESULTS: Biomass growth and enzyme production titres changed with a change in substrate concentration. Modelling analysis of biomass and enzyme production titres at different substrate concentrations revealed significant accuracy in terms of statistical consistency and robustness with respect to fermentation kinetic profiles. CONCLUSION: With the B. circulans strain used, an economic protease yield (2837 × 10³ U g^?1) with respect to biomass and glucose ratio was achieved at low substrate concentration (10 g L^?1). The developed model could be effectively utilised for designing, controlling and up‐scaling the protease production process in high‐density fermentation in selected bioreactors with statistical consistency. Copyright © 2008 Society of Chemical Industry     

An approach to the detection of synthetic milk in dairy milk: 3. Detection of vegetable oil and sodium bicarbonate

A high-performance thin layer chromatography (HPTLC) method for the detection of groundnut oil and palm oil, the main constituents of synthetic milk, was developed. The minimum detectable level of the oils was 80 mg/100 ml. The rosolic acid qualitative test was found to be sensitive enough to detect levels as low as 20 mg/100 ml sodium bicarbonate in milk.     

Imaging Surface Immobilization Chemistry: Correlation with Cell Patterning on Non‐Adhesive Hydrogel Thin Films

High‐fidelity surface functional group (e.g., N‐hydroxysuccinimide (NHS) reactive ester) patterning is readily and reliably achieved on commercial poly(ethylene glycol) (PEG)‐based polymer films already known to exhibit high performance non‐fouling properties in full serum and in cell culture conditions. NHS coupling chemistry co‐patterned with methoxy‐capped PEG using photolithographic methods is directly spatially imaged using imaging time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and principal components statistical analysis. Patterned NHS surface reactive zones are clearly resolved at high sensitivity despite the complexity of the polymer matrix chemistry. ToF‐SIMS imaging also reveals the presence of photo‐resist residue remaining from typical photolithography processing methods. High cross‐correlation between various ion‐derived ToF‐SIMS images is observed, providing sensitive chemical corroboration of pattern chemistry and biological reactivity in complex milieu. Surface‐specific protein coupling is observed first by site‐selective reaction of streptavidin with NHS patterns, followed by identical patterns of biotinylated Alexa‐labeled albumin coupling. This suggests that streptavidin immobilized on the patterns remains bioactive. Fluorescently labeled full serum is shown to react selectively with NHS‐reactive regions, with minimal signal from methoxy‐capped regions. Insufficient serum is adsorbed under any conditions to these surfaces to support cell attachment in serum‐containing media. This reflects the high intrinsic non‐adsorptive nature of this chemistry. Fibroblasts attach and proliferate in serum culture only when a cell adhesion peptide (RGD) is first grafted to NHS regions on the PEG‐based surfaces. Longer‐term serum‐based cell culture retains high cell‐pattern fidelity that correlates with chemical imaging of both the NHS and RGD patterns and also lack of cell adhesion to methoxy‐capped regions. Cell staining shows orientation of adherent cells within the narrow patterned areas. Cell patterns are consistently retained beyond 15 days in serum media.     

Effect of Method of Sample Preparation on Strength of Zirconium Diboride (ZrB<Subscript>2</Subscript>)

Different surface finish of ZrB₂ was generated by machining the hot pressed monolithic ZrB₂ by wire-electrical discharge machining (EDM) as well as conventional diamond grinding. The effect of surface finish on strength was studied. Our results showed that wire-EDM produced very high roughness (Ra = 1.2) as compared with diamond grinding (Ra = 0.2 and 0.33) which resulted into lower strength of ZrB₂ for EDM machined sample as compared to diamond ground samples.     

The composite electrolyte with an insulation Sm2O3 and semiconductor NiO for advanced fuel cells

Novel Sm₂O₃?NiO composite was prepared as the functional electrolyte for the first time. The total electrical conductivity of Sm₂O₃?NiO is 0.38 S cm^?1 in H₂/air condition at 550 °C. High performance, e.g. 718 mW cm^?2, was achieved using Sm₂O₃?NiO composite as an electrolyte of solid oxide fuel cells operated at 550 °C. The electrical properties and electrochemical performance are strongly depended on Sm₂O₃ and NiO constituent phase of the compositions. Notably, surprisingly high ionic conductivity and fuel cell performance are achieved using the composite system constituting with insulating Sm₂O₃ and intrinsic p-type conductive NiO with a low conductivity of 4 × 10^?3 S cm^?1. The interfacial ionic conduction between two phases is a dominating factor giving rise to significantly enhanced proton conduction. Fuel cell performance and further ionic conduction mechanisms are under investigation.     

Multiferroic BiFeO3 thin films for multifunctional devices

We report the metalorganic chemical vapor deposition of crystalline BiFeO3 films on platinized silicon substrates using n-butylferrocene, triphenylbismuth and oxygen. Based on thermogravimetric analysis data, the suitability of these two precursors for depositing BiFeO3 is discussed. The deposited films were characterized for structure and morphology using X-ray diffraction and scanning electron microscopy. Composition analysis using X-ray photoelectron spectroscopy revealed that the films were stoichiometric BiFeO3. Electrostatic force microscopy indicated that the film had polarizable domains that showed no deterioration in polarization over time long after electric poling. The film showed a saturation magnetization of 10 +/- 1 emu/cm3 at room temperature.     

Inhibition of Listeria monocytogenes by oregano, cranberry and sodium lactate combination in broth and cooked ground beef systems and likely mode of action through proline metabolism

Listeria monocytogenes is a food safety challenge in various food systems including fresh and frozen meat and poultry. Natural antimicrobials from plant sources in combination with salts of organic acids have the potential to control L. monocytogenes. In this research the efficiency of water soluble phenolic extracts of oregano and cranberry in combination with sodium lactate was evaluated for control of L .monocytogenes. In both broth and cooked meat studies, the results indicated that the combination of water soluble extracts of oregano and cranberry, at a ratio of 50:50 and a concentration of 750 ppm, with 2% sodium lactate had the best inhibitory effect in the tested strain. Based on the rationale that phenolics in oregano and cranberry behave as proline analogs, the potential recovery of pathogen growth in medium with the best inhibitor concentration and supplemented with 1 mM proline was evaluated. The results indicated that there was a proline-induced growth recovery, pointing to a possible mechanism of action of inhibitors, involving proline metabolism. These results confirm the potential of plant extracts to be antimicrobial, and when combined with sodium lactate, can be used as a nature constituent of multiple-barrier food preservation systems.     

Preparation and charge transport studies of chemically synthesized polyaniline

Polyaniline doped with p-toluenesulfonic acid was synthesized using in situ chemical oxidation method for optimization of synthesis parameters. For p-toluenesulfonic acid/aniline molar ratio of 5, the obtained polymer exhibits highest value of the electrical conductivity. The electrical conductivity of polyaniline doped with p-toluenesulfonic acid was measured in the temperature range of 30–300 K. The conductivity of polyaniline was found to increase with rise in the temperature. The measured conductivity versus temperature data was fitted with Arrhenius model, variable range hopping (VRH) model and Kivelson model in order to investigate the charge transfer mechanism in polyaniline. It is shown that conductivity observed over wide temperature range of 30–300 K follows Kivelson model obeying power law behavior.