Optimal control analysis of the dynamic growth behavior of microorganisms

Understanding the growth behavior of microorganisms using modeling and optimization techniques is an active area of research in the fields of biochemical engineering and systems biology. In this paper, we propose a general modeling framework, based on Monad model, to model the growth of microorganisms. Utilizing the general framework, we formulate an optimal control problem with the objective of maximizing a long-term cellular goal and solve it analytically under various constraints for the growth of microorganisms in a two substrate batch environment. We investigate the relation between long term and short term cellular goals and show that the objective of maximizing cellular concentration at a fixed final time is equivalent to maximization of instantaneous growth rate. We then establish the mathematical connection between the generalized framework and optimal and cybernetic modeling frameworks and derive generalized governing dynamic equations for optimal and cybernetic models. We finally illustrate the influence of various constraints in the cybernetic modeling framework on the optimal growth behavior of microorganisms by solving several dynamic optimization problems using genetic algorithms. (C) 2014 Published by Elsevier Inc.

Novel AgBr/Ag3PO4 Decorated Ceria Nanoflake Composites for Enhanced Photocatalytic Activity toward Dyes and Bacteria under Visible Light

The aim of this study was to develop heterogeneous visible light active photocatalysts using AgBr and Ag3PO4 using CeO2 nanoflakes as an efficient substrate. Ascorbic acid was employed as a fuel to synthesize fine ceria nanoflakes by a facile solution combustion process. AgBr and Ag3PO4 were decorated on ceria to prepare AgBr/Ag3PO4/ceria nanocomposites. The structure of the composite was determined by X-ray diffraction analysis. Novel flakelike morphology was revealed using electron microscopy techniques. The nanocomposites exhibit excellent photocatalytic activity under visible light compared to pristine ceria nanoparticles. The nanocomposite catalyst particles degraded both anionic and cationic dyes. It also exhibited efficient antimicrobial activity under visible light. The AgBr/Ag3PO4/ceria nanocomposite was characterized using X-ray diffraction analysis, diffuse reflectance spectroscopy, electron microscopy, BET surface area analysis, and X-ray photoelectron spectroscopy, and the reasons for enhanced photocatalytic activity were elucidated. The presence of silver based semiconductors on ceria has shown to decrease charge recombination through photoluminescence analysis that attributed for enhanced photocatalytic activity. The AgBr/Ag3PO4/ceria nanocomposite has shown a stable performance after many repeated cycles.

Epigenetics and miRNA during bacteria-induced host immune responses

Various cellular processes including the pathogen-specific immune responses, host-pathogen interactions and the related evasion mechanisms rely on the ability of the immune cells to be reprogrammed accurately and in many cases instantaneously. In this context, the exact functions of epigenetic and miRNA-mediated regulation of genes, coupled with recent advent in techniques that aid such studies, make it an attractive field for research. Here, we review examples that involve the epigenetic and miRNA control of the host immune system during infection with bacteria. Interestingly, many pathogens utilize the epigenetic and miRNA machinery to modify and evade the host immune responses. Thus, we believe that global epigenetic and miRNA mapping of such host-pathogen interactions would provide key insights into their cellular functions and help to identify various determinants for therapeutic value.

Biomineralization and Biobeneficiation of Bauxite

Role of indigenous microbes in the formation and conversion of bauxite minerals is illustrated. Many types of microorganisms such as fungi, heterotrophic and autotrophic bacteria and yeasts inhabit bauxite ore deposits bringing about biogenesis and biomineraliztion. Organisms capable of iron oxidation and reduction and solubilising calcium carbonate and silica can be isolated from bauxite deposits and are used to bring about selective mineral beneficiation to remove iron, calcium and silica. Use of Paenibacillus polymyxa in the efficient removal of calcium from low grade bauxites is demonstrated through bioreactor technology. Similarly, for iron removal from bauxite, iron-reducing bacteria can be used. Silicate bacteria aid in selective silica solubilisation to control alumina: silica ratios. Microorganisms can also be used to bring about environmental control with respect to red mud disposal through bioremediation technology.

Novel synergistic photocatalytic degradation of antibiotics and bacteria using V-N doped TiO2 under visible light: the state of nitrogen in V-doped TiO2

We report the synthesis of vanadium and nitrogen co-doped TiO2 for photocatalysis mainly emphasizing the state of nitrogen doping into TiO2 in the presence of vanadium ions. Considering the increase in antibiotic resistance developed by microbes due to the excess of pharmaceutical waste in the ecosystem, the photocatalytic activity was measured by degrading an antibiotic, chloramphenicol. A novel experiment was conducted by degrading the antibiotic and bacteria in each other's vicinity to focus on their synergistic photo-degradation by V-N co-doped TiO2. The catalysts were characterized using XRD, DRS, PL, TEM, BET and XPS analysis. Both interstitial and substitutional nitrogen doping were achieved with V-TiO2, showing high efficiency under visible light for antibiotic and bacterial degradation. In addition, the effect of doping concentration of nitrogen and vanadium in TiO2 and catalyst loading was studied thoroughly. Reusability experiments show that the prepared V-N co-doped TiO2 was stable for many cycles.