Microbial Technologies for Biofuels Production
One of the most promising routes to renewable 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. Despite extensive research efforts, the development of commercially viable CBP technology remains an elusive goal. We are addressing this challenge through the development of single microbe and microbial community technologies aimed at overcoming current obstacles to renewable fuels production. Our research involves a combination of cell culture experiments and detailed metabolic modeling to identify promising microbes and synthetic communities, to determine engineering targets in individual microbes and community interactions, and to develop bioreactor operating strategies that maximize fuel production. Current research projects and sponsors include: (1) construction of synthetic yeast communities for efficient sugar uptake and medium detoxification (ReCommunity Recycling); (2) solid-state fermentation of the lignin degrading fungus Phanerochaete chrysosporium to produce jet fuel precursors from lignocellulose (Navy); and (3) synthesis gas fermentation with Clostridium ljungdahlii andrelated bacteria for conversion of processed municipal solid waste to alcohol fuels (ReCommunity Recycling). These projects are organized through The Institute for Massachusetts Biofuels Research (TIMBR).
Emulsion and Nanoparticle Processing
Emulsions and nanoparticles are two important classes of colloids that have a very wide range of applications that span the petroleum, chemical, agricultural, pharmaceutical, foods and consumer/household products industries. A critical property of any colloidal dispersion is the particle size distribution, which affects dispersion rheology, stability, texture and appearance. The particle size distribution is affected not only by the chemical constituents but also by the processing method used to manufacture the dispersed particles. Colloidal 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 developing model-based strategies for streamlining the product/process development cycle to facilitate more rapid development and optimization of emulsion and nanoparticle processing technologies. A combination of designed experiments and modeling studies are used to predict and optimize process performance as a function of the chemical formation and processing conditions. Current research projects and sponsors include: (1) population balance equation modeling of high pressure homogenizers and colloid mills to predict the drop size distribution and viscosity of oil-in-water emulsions (Unilever); (2) development of solid lipid nanoparticle dispersions that remain stable at room temperature and effectively encapsulate lipophilic compounds (Procter and Gamble); and (3) transport modeling of pharmaceutical drying and filtration processes to predict the effect of the crystal size distribution on process performance (Sunovion). These projects are organized through the Center for Process Design and Control and the Process Systems Engineering Consortium.
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 approximately 20,0000 neurons that differ with respect 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 that generate oscillatory signals 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 rhythms in individual cells. The role of the ubiquitous neurotransmitter γ-aminobutyric acid (GABA) in the SCN network is less clear, with early studies arguing that GABA enhances synchronization while more recent studies suggest that GABA actually opposes synchronization to enhance the ability of the SCN to entrain to external light-dark cycles. Using data generated by our experimental collaborator Erik Herzog(Washington University), we are attempting to rationalize these findings by developing multicellular models based on multiscale descriptions of individual neurons to better understand VIP and GABA mediated intracellular communication within the SCN. This project is supported by the National Institutes of Health.