Saurav Datta

Reactive nanostructured membranes for water purification

Many current treatments for the reclamation of contaminated water sources are chemical-intensive, energy-intensive, and/or require posttreatment due to unwanted by-product formation. We demonstrate that through the integration of nanostructured materials, enzymatic catalysis, and iron-catalyzed free radical reactions within pore-functionalized synthetic membrane platforms, we are able to conduct environmentally important oxidative reactions for toxic organic degradation and detoxification from water without the addition of expensive or harmful chemicals. In contrast to conventional, passive membrane technologies, our approach utilizes two independently controlled, nanostructured membranes in a stacked configuration for the generation of the necessary oxidants. These include biocatalytic and organic/inorganic (polymer/iron) nanocomposite membranes. The bioactive (top) membrane contains an electrostatically immobilized enzyme for the catalytic production of one of the main reactants, hydrogen peroxide (H2O2), from glucose. The bottom membrane contains either immobilized iron ions or ferrihydrite/iron oxide nanoparticles for the decomposition of hydrogen peroxide to form powerful free radical oxidants. By permeating (at low pressure) a solution containing a model organic contaminant, such as trichlorophenol, with glucose in oxygen-saturated water through the membrane stack, significant contaminant degradation was realized. To illustrate the effectiveness of this membrane platform in real-world applications, membrane-immobilized ferrihydrite/iron oxide nanoparticles were reacted with hydrogen peroxide to form free radicals for the degradation of a chlorinated organic contaminant in actual groundwater. Although we establish the development of these nanostructured materials for environmental applications, the practical and methodological advances demonstrated here permit the extension of their use to applications including disinfection and/or virus inactivation.

Effect of Pre‐Filtration on Selective Isolation of Tat Protein by Affinity Membrane Separation: Analysis of Flux, Separation Efficiency, and Processing Time

Abstract The isolation and purification of Tat protein from bacterial lysate using avidin‐biotin interaction in microfiltration membranes have been reported in the literature. To increase the efficacy of the technique, improvements in flux, Tat separation efficiency, and processing time are essential. In the current research work a pre‐filtration step was introduced to remove unwanted high molecular weight proteins and other impurities from feed prior to affinity membrane separation. Significant enhancement in flux and separation efficiency of Tat was observed. Processing time was also reduced significantly. For example, with UF pretreatment step the total Tat recovery was around four times higher (with processing time 25% lower) than that observed with the untreated feed. The quality of purified Tat was analyzed by SDS‐PAGE, Western Blot, and biotin analysis. Flux behavior in affinity separation was described by model equations.

An attempt towards simultaneous biobased solvent based extraction of proteins and enzymatic saccharification of cellulosic materials from distiller's grains and solubles

Distillers grains and solubles (DGS) is the major co-product of corn dry mill ethanol production, and is composed of 30% protein and 30-40% polysaccharides. We report a strategy for simultaneous extraction of protein with food-grade biobased solvents (ethyl lactate, d-limonene, and distilled methyl esters) and enzymatic saccharification of glucan in DGS. This approach would produce a high-value animal feed while simultaneously producing additional sugars for ethanol production. Preliminary experiments on protein extraction resulted in recovery of 15-45% of the protein, with hydrophobic biobased solvents obtaining the best results. The integrated hydrolysis and extraction experiments showed that biobased solvent addition did not inhibit hydrolysis of the cellulose. However, only 25-33% of the total protein was extracted from DGS, and the extracted protein largely resided in the aqueous phase, not the solvent phase. We hypothesize that the hydrophobic solvent could not access the proteins surrounded by the aqueous phase inside the fibrous structure of DGS due to poor mass transfer. Further process improvements are needed to overcome this obstacle.

In Silico Designing of an Industrially Sustainable Carbonic Anhydrase Using Molecular Dynamics Simulation

Carbonic anhydrase (CA) is a family of metalloenzymes that has the potential to sequestrate carbon dioxide (CO2) from the environment and reduce pollution. The goal of this study is to apply protein engineering to develop a modified CA enzyme that has both higher stability and activity and hence could be used for industrial purposes. In the current study, we have developed an in silico method to understand the molecular basis behind the stability of CA. We have performed comparative molecular dynamics simulation of two homologous α-CA, one of thermophilic origin (Sulfurihydrogenibium sp.) and its mesophilic counterpart (Neisseria gonorrhoeae), for 100 ns each at 300, 350, 400, and 500 K. Comparing the trajectories of two proteins using different stability-determining factors, we have designed a highly thermostable version of mesophilic α-CA by introducing three mutations (S44R, S139E, and K168R). The designed mutant α-CA maintains conformational stability at high temperatures. This study shows the potential to develop industrially stable variants of enzymes while maintaining high activity.

Chapter 6:Separations Technologies for Biobased Product Formation—Opportunities and Challenges

Recent years have witnessed a major thrust moving towards a sustainable, biobased economy using a biorefinery concept. The biorefinery concept is based on obtaining a broad spectrum of biofuels and value-added biobased products from renewable resources—analogous to the petroleum refinery concept. It has two major components—environmentally benign conversion technologies and efficient separations technologies. Separations technologies are important as they contribute to 30–50% of the overall production cost. Due to higher financial incentives, there is a surging interest for commercializing value-added biobased products, which function as precursors or building blocks for industrially relevant downstream chemicals. Particularly, oxygenated biobased species, such as alcohols, organic acids and furans, due to their reactive nature, are of great interest. We embrace this opportunity and designed this chapter focusing on separations technologies that are relevant to biobased product formation. Both fundamental aspects of separations technologies and their state-of-the-art applications for biobased product formation are emphasized. Since this is an emerging area of research and commercialization, none of the technologies are devoid of limitations. Therefore, we discuss the technical challenges and potential solutions associated with the technologies. We believe that this chapter will function as a guideline for identifying suitable separations schemes for biobased product formation.