Constraints based analysis of extended cybernetic models

The cybernetic modeling framework provides an interesting approach to model the regulatory phenomena occurring in microorganisms. In the present work, we adopt a constraints based approach to analyze the nonlinear behavior of the extended equations of the cybernetic model. We first show that the cybernetic model exhibits linear growth behavior under the constraint of no resource allocation for the induction of the key enzyme. We then quantify the maximum achievable specific growth rate of microorganisms on mixtures of substitutable substrates under various kinds of regulation and show its use in gaining an understanding of the regulatory strategies of microorganisms. Finally, we show that Saccharomyces cerevisiae exhibits suboptimal dynamic growth with a long diauxic lag phase when growing on a mixture of glucose and galactose and discuss on its potential to achieve optimal growth with a significantly reduced diauxic lag period. The analysis carried out in the present study illustrates the utility of adopting a constraints based approach to understand the dynamic growth strategies of microorganisms. (C) 2015 Elsevier Ireland Ltd. All rights reserved.

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.