Professor, Director of the Center for Process Design and Control, and Co-director of the Institute for Massachusetts Biofuels Research
B.S., Chemical Engineering, University of Colorado, Boulder, 1985
M.S., Chemical Engineering, University of Texas, Austin, 1988
Ph.D., Chemical Engineering, University of California, Santa Barbara, 1992
Career Development Award, National Science Foundation, 1995
Research Fellowship, Alexander von Humboldt Foundation, 2001
College of Engineering Outstanding Senior Faculty Award, UMass, 2008
Associate Editor, Journal of Process Control
Associate Editor, Automatica
Associate Editor, IET Systems Biology
Academic Trustee, CACHE Corporation
Process Design and Control Center (PDCC)
Process Systems Engineering Consortium (PSEC)
The Institute for Massachusetts Biofuels Research (TIMBR)
Current Focus of Research
Microbial Technologies for Biofuels Production
One of the most promising routes to renewable liquid fuels is the conversion of lignocellulosic biomass by microbial organisms. The development of consolidated bioprocessing (CBP) technology requires a microbe that efficiently degrades lignocellulose into fermentable substrates, rapidly uptakes both pentose and hexose sugars as well as their oligomers, and converts available substrates to the targeted fuel at high yield, titer and productivity. Most current research efforts are aimed at identifying and engineering individual microbes with all these capabilities. Despite extensive research efforts, the development of commercially viable CBP technology remains an elusive goal. A promising alternative is to develop synthetic consortia comprised of a few well characterized and easily engineered microbes that collectively achieve CBP. More specifically, synergistic combinations of lignocellulose degrading microbes and biofuel synthesizing microbes may prove to be particularly effective for liquid fuels production. We are performing fermentation experiments and developing metabolic models of synthetic consortia to efficiently convert lignocelullose to ethanol. This project is supported by the UMass Institute for Cellular Engineering.
Integrated Product and Process Design of Emulsified Products
Oil-in-water emulsions have a wide variety of applications including cosmetics, creams, lotions, agricultural products, and hydrophobic compound encapsulation and delivery. In the foods industry, emulsions constitute numerous natural as well as processed products such as milk, butter, margarine, sauces and desserts. The drop size distribution affects several important emulsion properties including rheology, stability, texture and appearance. Emulsions are typically formed by low-shear mixing in an agitated vessel followed by processing in high-shear device such as a high pressure homogenizer to create drops in the targeted range. Due the lack of suitable predictive models, emulsified products are currently developed by combining a broad knowledge of previous product formulations with empirical scientific experimentation to create new formulations with desired properties. We are performing homogenization experiments and developing population balance equation models to predict the drop size distribution and enable more systematic design of emulsion formulations and processing conditions. This project is supported by the National Science Foundation and Unilever through the Process Design and Control Center.
Stabilization of Solid Lipid Nanoparticles
Solid lipid nanoparticles (SLNs) have great potential as delivery systems for the encapsulation, protection, and release of active lipophilic compounds (e.g., drugs, nutraceuticals, antimicrobials, antioxidants, and vitamins) in the pharmaceutical, food, personal care, and agro-chemical industries. SLNs are commonly prepared by making an oil-in-water nanoemulsion using high pressure homogenization followed by controlled cooling so that the fluid lipid droplets crystallize and produce solid lipid nanoparticles (r < 100 nm). SLNs offer several advantages for encapsulation of active components including improved physical stability, protection to chemical degradation, and precise control over release rates. A major obstacle to the widespread industrial use of SLNs is their tendency to aggregate and form gels when stored at ambient temperatures. We are performing targeted experiments and developing population balance equation models to better understand SLN instability with the goal of engineering the surfactant system and processing conditions to minimize aggregation. This project is supported by Procter & Gamble through the Process Design and Control Center.
Filtering and Drying Processes in the Pharmaceutical Industry
Filtration and drying are critical downstream processes in pharmaceutical manufacturing. These liquid-solid separations are subject to stringent constraints because the active pharmaceutical ingredient (API) must not be affected by processing. Because pharmaceutical manufacturing is typically accomplished through batch operation, overall process productivity is strongly affected by the batch times of the individual unit operations. For example, in drying processes the API can degrade if the drying temperature is too high while long batch times can result if the temperature is too low. Drying often represents a manufacturing bottleneck because the moisture content of the wet cake is difficult to measure in real time. As a result, the drying process may be run far longer than necessary to ensure that the moisture content drops to an acceptable level. Similar challenges are encountered in filtration processes, where the most favorable operating strategy is difficult to determine with commonly available measurements. We are performing experiments with state-of-the-art, on-line analytical techniques and developing process models that allow filtration and drying performance to be predicted and optimized. This project is supported by Sunovion through the Process Design and Control Center.
Multiscale Modeling and Analysis of Circadian Rhythm Generation and Synchronization
In mammals, many physiological and behavioral events are subject to well controlled daily oscillations. These rhythms are generated by an internal self-sustained oscillator located in the hypothalamic suprachiasmatic nucleus (SCN). The SCN consists of a broad range of neural subgroups, differentiated according to their neuropeptide content, their afferent and efferent connections with other regions of the brain, and their oscillatory behavior. Circadian rhythmicity is ensured not only by autonomous intracellular mechanisms within individual cells but also by intercellular communication that coordinates these functionally and structurally distinct cell types across the SCN. Vasoactive intestinal polypeptide (VIP) is a critical neuropeptide involved in intercellular communication and the synchronization of circadian rhythm. The neurotransmitter γ-aminobutyric acid (GABA) has also been proposed to involved in synchronization of the SCN network. We are developing multicellular models based on multiscale descriptions of individual neurons to better understand VIP and GABA mediated intracellular communication within the SCN. Our collaborators are Frank Doyle (UCSB), Erik Herzog (Washington University) and Linda Petzold (UCSB). This project is supported by the National Institutes of Health.
Aggregation Dynamics in Plant Cell Suspension Cultures
Plant cell culture is an alternative production technology for complex natural products that cannot be chemically synthesized or extracted in high yields from native sources. Suspension cultures consisting of undifferentiated plant cells are attractive industrially, especially compared to other types of plant cell culture such as differentiated cultures and transfected hairy root cultures, due to their relative similarity to microbial cell culture systems. A unique characteristic of plant cell cultures is the tendency of the cells to grow as multicellular aggregates. The effect of aggregate size on metabolic activity has been studied extensively, but no definitive trend regarding secondary metabolite production has emerged across species and cell culture systems. Aggregate size has been shown to affect culture growth rates and rheological properties of the culture broth. We are performing Taxus cell culture experiments and developing population balance equation models to better understand and ultimately engineer the aggregation process for increased production of the anti-cancer agent paclitaxel. Our collaborator is Susan Roberts (UMass). This project is supported by the National Science Foundation.