Research

Jonathan S. Dordick

Areas of Research:

Our research is broadly in the areas of enzyme technology and biochemical engineering. Much of our effort is focused on designing enzymes and enzyme systems to operate under harsh conditions such as those found in more conventional chemical processing. Nevertheless, we strive to maintain the extraordinary selectivity and reactivity that are the hallmark of enzymatic catalysis. While conventional enzyme technology (i.e., catalysis in aqueous solutions under ambient conditions) falls short in being able to utilize biocatalysts under the extreme conditions typically found in chemical processing, we have focused on enhancing the capabilities of enzymes which can function under unconventional conditions. This includes the application of enzymes in organic solvents, under high pressures, at extremes in temperatures, and at high ionic strengths. Specifically, in numerous projects, we are investigating the structure and function of enzymes in organic solvents to design biocatalysts with high stabilities and activities in this unnatural environment. This work involves the elucidation of kinetics, enzyme secondary and tertiary structure, and dynamics in solvents with vastly different physicochemical properties. Our results over the past few years have enabled us to prepare enzymes with extraordinarily high activities and stabilities in nearly anhydrous systems. For example, in collaboration with Douglas Clark at U. C. Berkeley, we have found that simply lyophilizing enzymes out of an aqueous salt solution results in enzyme activities in hexane nearly as high as that in water. This finding demonstrates that enzymes in organic solvents can have native-like reactivity and shows that biocatalyst engineering can be done simply and without extensive preparation.

In another example of biocatalyst engineering, we have discovered that enzymes can be dissolved in organic solvents through the use of surfactant ion pairing. As with the salt-activated preparations, the ion-paired organic solvent-soluble preparations show reactivity in solvents nearly as high as in water. This approach also led us to develop enzyme-polymer composites, wherein enzymes are incorporated into polymer matrices that comprise common plastics, paints, and coatings. Such "biocatalytic plastics" have found application as highly active and stable catalysts for biotransformations, antifouling paints and coatings, and as highly selective adsorbents for affinity chromatography. Finally, in combination with biocatalyst engineering, we are exploring the use of protein engineering and directed molecular evolution to design new selectivities and activities from common enzymes used in biotransformations.

In addition to enzyme engineering, we have an extensive program underway in the use of enzymes as catalysts for polymer synthesis. In particular, we have prepared novel sugar-based materials for use as water absorbents, drug delivery matrices, and enzyme immobilization supports. These materials are prepared via the combined action of biocatalysis and chemical synthesis (e.g., chemoenzymatic synthesis) and have been used as hydrogels with unique properties. Such properties include the ability to swell greater than 1,000-fold in water, limited dependence of swelling on the ionic strength of the solution, and reduced binding of proteins on the sugar-based polymeric network.

In a related area, enzymes from agricultural sources have been identified as potentially useful biocatalysts. For example, peroxidase from soybean hull is being used to prepare redox-active polymers for use in thin redox films and batteries. This enzyme also catalyzes the rapid synthesis of polyphenols. When prepared in a combinatorial fashion, these polyphenols can be displayed in an array-based format that forms the basis of a sensor element for toxic metal and vapor detection. Peroxidases are also being used to catalyze the oxidation of nonphenolic compounds that constitute common pollutants, and reactors are being developed to improve the ability of enzymes to be used in large-scale bioremediation efforts.

The exquisite selectivity of protein-protein interactions are being used in the design of a bioseparations technique that links the extraordinary selectivity of affinity interaction with the ease and scalability of liquid-liquid extraction. This approach is known as ARMES (Affinity-based Reversed-Micellar Extraction and Separation) and has employed lectins to resolve efficiently and rapidly glycoform variants from complex biological mixtures.

Finally, together with Douglas Clark and scientists from EnzyMed, Inc. (a drug discovery company in Iowa City, IA), we are using enzymes synthetically in a combinatorial fashion. This technology, known as "combinatorial biocatalysis" is being used in concert with high throughput robotics to rapidly synthesize small molecules for use in pharmaceutical and agrochemical applications. We are presently extending this to the synthesis of specialty monomers for the rapid synthesis of polymeric materials for use in the chemical and pharmaceutical industries.