Durgesh Prasad Kavishvar
Doctor of Philosophy
Department of Chemical Engineering University of Toronto
Abstract
Yield stress is a characteristic stress depicting the flow behavior of many complex materials. When the applied shear stress is lower than yield stress, materials exhibit solid-like behavior, transitioning to liquid-like behavior for shear stress>yield stress. Conventional rheometers often struggle with sensitivity in measuring low yield stress, lack real-time measurement capabilities, and are prohibitively expensive. These limitations are particularly pronounced in biological materials such as blood and mucus, where variations in yield stress can signify underlying health conditions. For instance, yield stress of blood from patients with cerebrovascular and cardiovascular diseases, hypertension, sickle cell disease, among others, exceeds that of healthy blood. Similarly, yield stress of mucus from individuals battling conditions such as cystic fibrosis or asthma can be several orders of magnitude higher than that of healthy lung mucus. Also, yield stress measurements prove valuable for quality assessment in various industries such as oil & gas as well as food industry.
In this work, we investigate, through experiments, scaling analysis, and simulation, the yielding behavior of various complex materials in a Hele-Shaw microfluidic extensional flow device (MEFD). We propose the MEFD as a new microfluidic rheometer capable of measuring a low yield stress ranging from 5 mPa−5 Pa. The design of the MEFD is such that it enables a gradient in shear stress, shear stress, such that shear stress is lower near the center or stagnation point, and higher away from the stagnation point. For a yield stress fluid, we observe that, below a certain flow rate, shear stress exceeds yield stress only in the outer region, leading to stagnation or unyielding of the fluid in the inner region. Our simulation study also corroborates the experimental findings, demonstrating the existence of an unyielded region near the stagnation point of the extensional flow. We apply scaling analysis to deduce yield stress by measuring this size of the unyielded region at center. We validate the scaling relationship using Carbopol solutions of various concentrations (0.015 to 0.3%), measuring yield stress as low as ~10 mPa to ~1 Pa, and comparing these measurements with a standard rheometer.
Furthermore, we showcase the applicability of our rheometer by measuring yield stress of human blood samples ranging between 30−80 mPa for a range of hematocrits as well as yield stress of porcine gastric mucins (20%) of 0.7 Pa. We also demonstrate measurements of yield stress of clay suspensions (2 to 6%), useful in oil & gas applications. We also show a proof of concept for food industry by measuring yield stress of a lactic drink of roughly 7 mPa. Our microfluidic rheometer offers several other advantages, including real-time measurement capability (with measurement time as short as 4 s), low volume requirement (<1 ml), ease of cleaning and reuse, and cost-effectiveness. Therefore, it attracts diverse applications in clinical research, particularly in disease detection, as well as in industries such as food and oil & gas for quality assessment.
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A U of T Engineering startup co-founded by Adnan Sharif (ChemE MEng student) has its roots in an experience that is all too common for many of us — he kept forgetting to water his plants.
“I was working in a plant immunity biology lab, so if I didn’t water them, I’d have no plants to do experiments with,” says Sharif.
At the time, Sharif was a U of T undergraduate student working with Professor Keiko Yoshioka in the Department of Cell & Systems Biology. He has since graduated and is now pursuing an MEng in the Department of Chemical Engineering & Applied Chemistry.
“My dad is a mechanical engineering professor at a university in Japan, and he knows a lot about manufacturing materials with porous, three-dimensional structures. So that’s how I got the idea to make my own 3D printed soil construct, which could retain water for a week or more. That way, I wouldn’t have to go into the lab and water the plants so often.”
Today that product is called SmartSoil, and it’s one of the key innovations at the heart of Lyrata, a startup that is producing edible crops for caterers and high-end restaurants across the Greater Toronto Area.
Support from the U of T Engineering community has been key to Lyrata’s success. For example, it was a U of T Engineering alumni connection that recently led to Lyrata launching an installation at Casa Loma, a historic museum and landmark in midtown Toronto.
Abstract
Algae have long been promoted as alternative hosts for sustainable biotechnology concepts owing to their capacity for light-driven circular reuse of waste streams as inputs and the production of biomass rich in valuable natural products. The emerging capacity to tailor algal cell metabolism through genetic engineering for the sustainable production of desired biochemicals holds the promise of co-product generation from algal bioprocesses to multi-valorize waste inputs. Microalgal metabolic engineering has emerged in recent years due to the intersection of reliable DNA synthesis and improved understanding of transgene expression limitations, especially in the model green microalga Chlamydomonas reinhardtii. This alga has been a powerful workhorse for demonstrating the possibilities of eukaryotic algal metabolic engineering, especially for isoprenoid targets. Other eukaryotic microalgae are also coming to light as potential hosts for synthetic biology mediated genetic engineering concepts. The model red microalga Cyanidioschyzon merolae 10D is a polyextremophilic member of the Cyanidiophyceae that grows at pH 0.5-2 and 42-50 ˚C, lacks a cell wall, and can be cultured with low risk of contamination. C. merolae exhibits favorable genetic features such as targeted transgene integration by homologous recombination into its small nuclear genome (16 Mb) and few introns. We have recently developed a new, completely synthetic, molecular toolkit for transformation of the nuclear genome of this alga. In this presentation I will highlight advances in its metabolic engineering for heterologous generation of several products in addition to its cultivation outdoors on the mid Red Sea coast in 1000 L tubular photobioreactors. I will also describe our engineering strategies to expand the capacity of C. reinhardtii and C. merolae as green cell factories, highlight new developments in bio-process designs, the value of metabolic engineering for fundamental understanding of algal metabolism, and discuss the value of regional considerations for algal biotechnology in the Middle East.
Speaker Bio
Dr. Kyle J. Lauersen is an Assistant Professor at King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia. His group is named Sustainable & Synthetic Biotechnology with their main research focussed on engineering algae to be green cell factories. Kyle did his Doctorate of Natural Sciences at Bielefeld University in Germany, and his master’s as well as undergrad at Queen’s University in Kingston, Ontario, Canada.
Abstract
System Mapping is a set of structured visualization techniques that help groups and individuals to look at the relationships and underlying assumptions of complex systems. Systems Mapping can be useful for researchers as they seek to understand the social, environmental and economic context in which their research sits – critical information when trying to bring new ideas to market or to assess the sustainability of a new technology. This interactive seminar will introduce systems mapping, share some real world examples where mapping has been used, and invite participants to generate and share simple maps related to their own research.
Speaker Bio
Professor Emily Moore is the Director of the Troost Institute for Leadership Education in Engineering (ILead) at the University of Toronto where she researches how engineers lead as they deliver new technologies to market. Emily holds a bachelor’s in engineering chemistry (Queen’s) and a doctorate in physical chemistry (Oxford) and is a licensed professional engineer. Emily launched her career at the Xerox Research Center of Canada (XRCC), then joined engineering consulting firm Hatch where she led the water business and technology development portfolio. Emily holds 21 patents and is a Fellow of the Canadian Academy of Engineering. Emily’s leadership in industry was recognized with the 2016 Kalev Pugi Award (SCI Canada) and she was named one of 100 Global Inspirational Women in Mining by Women in Mining UK. Emily serves as a board member of Chemtrade Logistics, International Petroleum Corporation, and the Canadian Mining Innovation Council.
Abstract
Fischer-Tropsch (FT) synthesis is one of the largest-scale catalytic processes, where long-chain hydrocarbons are formed from syngas (CO and H2) by a combination of C-O activation and C-C coupling steps. Interest in sustainable aviation fuels is driving a renaissance of this century-old process. Typically, supported cobalt catalyst are preferred due to their high activity, selectivity towards long-chain hydrocarbons, and low CO2 selectivity. The nature of the active sites and the reaction network, consisting of C-O bond scission, C-C bond formation and hydrogenation steps, remain intensely debated, hampering the development of selective catalysts.
To investigate possible reaction mechanisms, a dual-site microkinetic model, agnostic to a preferred reaction mechanism, was constructed using reaction free energies and activation energies computed with VdW-DF density functional theory. To accurately capture the reaction environment, the effect of the CO saturation coverage was included in all calculations and in the microkinetic model construction. This approach proved to be critical to provide an accurate description of the kinetics under reaction conditions. Our first principles microkinetic model accurately captures the activity, selectivity and chain growth of the FT reaction.
Speaker Bio
Mark Saeys obtained his PhD from Ghent University in 2002. From 2003 to June 2014 he was a professor of chemical engineering at the National University of Singapore. Since July 2014, he is a full professor at the Laboratory for Chemical Technology at Ghent University, Belgium. During his PhD, he was a visiting scientist with Matt Neurock at the University of Virginia and with Bill Green at the Massachusetts Institute of Technology. For his work on gas phase radical chemistry, he received the ExxonMobil Chemical Benelux Award in 2002 and the Richard A. Glenn Award in 2003. In Singapore, he was the Associate Director for academics in the Singapore-MIT Alliance-Chemical and Pharmaceutical Engineering program and a visiting professor of chemical engineering at the MIT. In 2013, he received the prestigious Odysseus Award from the Research Foundation-Flanders to establish a research program on modelling-guided catalyst design at Ghent University. While in Singapore, he was one of the authors of the Carbon Capture and Storage/Utilization Roadmap for Singapore. In Belgium, he was a co-author of “The Chemical Route to a CO2-neutral World”, a Viewpoint published by the Royal Flemish Academy of Belgium. His research combines modelling-guided catalyst design with experimental kinetic validation and state-of-the-art characterization to unravel and optimize catalytic processes.
Abstract
Microfluidics exploits fluids and their physical and chemical properties at the microscale, enabling miniaturized platforms that offer lower cost, faster pace, higher performance, and increased portability than their macroscale counterparts. This talk will briefly discuss three research themes including droplet microfluidics, microwave sensing and soft robotic wearable systems.
- Two-phase droplet microfluidics employs monodispersed water-oil emulsions as mobilized test tubes to perform high throughput analysis (HTA). Despite numerous novel technologies reported, the adoption of droplet microfluidics as an HTA tool by non-microfluidics experts has not been seen. Modular-based droplet microfluidics, enabling easy assembly of application-specific systems, presents tremendous potential to break this barrier. This talk will introduce our work towards this goal including, a suite of physical models that can serve as design tools for passive-based droplet modules such as droplet generators, mergers, sorters and heaters, and a unique active droplet microfluidics method that relies on visual feedback of droplet position to actuate a pressure source to actively control individual droplets realizing functional modules.
- Simultaneous sensing and heating of individual droplets are critical but very challenging. Microwave resonators present tremendous potential to meet this need which will be the second part of this talk. Microwave sensing finds various applications beyond droplet microfluidics. Its applications for the detection of virus such as SARS-CoV-2 and E. coli as well as metal ions will be discussed.
- Soft robotic wearable systems offer hope to improve the quality of life for those in need because of their compliance nature. Most existing systems are expensive, power intensive and tethered to external power sources, limiting user mobility. Microfluidics enables miniaturization of the system including its front end (e.g. wearable sleeves) and back end (control unit), translating to low cost, tetherless and energy-efficient operation. This talk will present wearable sleeves for treating lymphedema, arthritis, and pressure ulcers due to the ill fit of prosthetic sockets.
Speaker Bio
Dr. Ren received her PhD in Mechanical Engineering from the University of Toronto and her master’s and bachelor’s degrees in Mechanical Engineering from Harbin Institute of Technology. She is currently a Professor of Mechanical and Mechatronics Engineering at the University of Waterloo (UW) and holds a Tier I Canada Research Chair (CRC) in Microfluidic Technologies. She is directing Waterloo Microfluidics Laboratory focusing on advancing fundamental knowledge of microfluidics and developing technologies that are impactful on a wide range of applications such as life science research, protein fractionation towards drug screening, water quality sensing and assistive technology for well-being. Besides the CRC, Dr. Ren has also received several awards from the engineering and research community, including: election as a Member of Canadian Institute of Engineering in 2024, election as a Member of Canadian Academy of Engineering in 2023, recognition as one of Canada’s 100 Most Powerful Women in 2021, election as a Member of the College of New Scholars, Scientists and Artists of Royal Society of Canada in 2018, being recognized as one of 20 leading female innovators in Women of Innovation (Dr. Ren is a co-founder of four start-up companies) in 2017.
Abstract
Biomanufacturing is a diverse industry, encompassing several well known processes such as antibiotics and fine chemicals. Canada has a long history of biomanufacturing which started in the 1920’s with the discovery of insulin for treatment of diabetes, launching what was the Connaught Lab which then went on to become part of Sanofi. Connaught Lab was also the first to develop combo vaccine making DPT in the 1940s and then playing a role in Polio vaccine development.
The talk will provide a flavor on the important groups of biologicals manufactured using animal/mammalian cells. Aspects of vaccine and antibody manufacturing as well as the advances in Cell and Gene therapy will be discussed.
Speaker Bio
Cynthia Elias is presently the Vice President, Operations at CCRM, Toronto. She has several years of experience in the field of animal/mammalian cell culture processes, including more than a decade of GMP commercial biological manufacturing at Sanofi. Prior to joining CCRM she held the position of Director, Manufacturing at the Government of Canada’s (NRC) Biological Manufacturing Center in Montreal, QC. Cynthia started in the Process development group at Sanofi working on new vaccines and clinical manufacturing and then moved on to commercial manufacturing. Cynthia was responsible for different departments within the bulk manufacturing of Inactivated Polio Vaccine (IPV). Before joining Sanofi, Cynthia worked at the National Research Council (NRC) in Montreal, in different positions of increasing responsibilities, from NSERC visiting scientist, Research Officer and Project Leader, leading a team working in the area of recombinant protein and viral vector production. Cynthia has experience in Biologics manufacturing from 5L to 1000L scale processes, including viral process for baculovirus, therapeutic cancer vaccines, AAV. Cynthia also has Regulatory and auditing experience with Health Canada, US FDA, and other regulatory agencies in Europe and other markets. Cynthia Elias holds a double Master’s and Ph.D. degree in Biotechnology from the University of Pune, India and, completed post-doctoral research at the Chemical Engineering Department, University of Colorado, at Boulder, USA. She has published several scientific articles in peer reviewed journals including book chapters and reviews. Actively involved in Biotechnology education programs in collaboration with the University of Toronto, York University (Markham Campus) and the University of Western Ontario (Adjunct Professor).
Final Oral Exam Seminar: Exploring the Specificity and Diversity of Reductive Dehalogenase Enzymes for Improved Bioremediation (Katherine Picott)
When: October 18, 2024 @9:00 – 9:25 a.m.
Place: Wallberg #407
Teams:
Meeting ID: 224 024 752 344
Passcode: iUBk6Z
Abstract:
Industrialization has caused the rapid development and production of organohalide compounds, resulting in their mass contamination in the environment where they are recalcitrant to degradation and pose serious health risks. Bioremediation emerged as a solution to remove chlorinated solvents that contaminate groundwater. The process invokes the activity of the reductive dehalogenase (RDase) enzyme family, which removes halogens from their substrates to ultimately detoxify them. RDases are found in diverse environments, including many anthropogenic waste treatment facilities, but their characterization is dominated by representatives associated with chlorinated solvents, and even these have modest characterization. The primary bottleneck in studying RDases is their production as they have been uncooperative in heterologous expression. This limitation not only slows the study of RDases, but prevents studies that rely on gene manipulation like structure-function investigations and restricts characterization to RDases that express under lab settings.
This work aims to enhance the characterization of the RDase family, addressing both detailed specifics and broader perspectives. First, a system for RDase expression in E. coli is developed by addressing the need for RDases’ two cofactors: cobalamin and iron-sulfur clusters. In co-expressing the RDase with a cobalamin uptake pathway, the active expression of six Dehalobacter RDases was achieved. This system allowed for kinetic and mutagenic studies for highly similar chloroalkane RDases. These comparative studies highlight the nuanced way in which RDases interact with and select their substrates
and identify residues as hot spots for manipulation. Additionally, mining RDases from anthropogenic waste facilities emphasized that the current knowledge of the RDase family is only scratching the surface. The global presence and diversity of RDases reveal an untapped potential for discovering methods to remove the concerning, emerging organohalide contaminants.
Overall, this work provides a comprehensive framework for the characterization of the RDase family and will accelerate our understanding of these enzymes. The findings lay a strong foundation to enable the discovery and design of RDases and advance their application in the removal of persistent contaminants.
Abstract
The concept of oxy-fuel combustion involves using O2 separated from air to burn a fuel to generate a CO2 rich stream that can then be sequestered. However, if only O2 is fed into the boiler, the combustion temperature will be too high. In practice, flue gas would need to be cooled to condense out water and then a part of the CO2 rich flue gas is recycled and mixed with the O2 as the feed oxidant to the combustion system. The remaining CO2 rich gas (>90% CO2) can be compressed and sequestered or further purified and used as new uses for CO2 are developed.
There are three different combustion systems found in pulp mills:
- Kraft recovery boiler for burning black liquor
- Lime kiln for driving CO2 from CaCO3 to generate CaO
- Biomass boiler where bark and reject wood from pulping are burned
In this presentation I will talk about the early research in oxyfuel combustion in kraft recovery boilers and lime kilns and some of the process and process chemistry implications of transitioning from traditional combustion with air to oxyfuel combustion.
Speaker Bio
Nikolai De Martini is an Associate Professor of Chemical Engineering and Director of the Pulp and Paper Centre at the University of Toronto. He joined the faculty in 2017. Prof. De Martini earned a PhD in Chemical Engineering for work on nitrogen and sulfur chemistry in kraft recovery boilers at Åbo Akademi University in Turku, Finland. He currently leads the industrial consortium Effective Energy and Chemical Recovery in Pulp and Paper Mills which is supported by pulp and paper companies in Canada, the United States, Brazil, Chile, Finland and Sweden.
Abstract
Viruses are the most abundant microbial entity on the planet, impacting microbial community structure and ecosystem services. Viruses infecting bacteria and archaea have been specifically understudied in engineered environments. Using metagenomic and computational biology methods, we examined the diversity, host-interactions, and genetic systems of viruses across three North American landfills. From giant viral genomes to streamlined CRISPR-Cas systems, municipal landfills housed unique, and surprising viral ecology. Landfills, as heterogeneous contaminated sites with unique selective pressures, are key locations for diverse viruses and atypical virus-host dynamics.
Speaker Bio
Dr. Laura Hug: Associate Professor and Canada Research Chair in Environmental Microbiology. Department of Biology at the University of Waterloo.
Dr. Hug’s research examines the diversity and function of microbial communities in contaminated sites using a combination of ‘omics approaches and enrichment culturing. Current research in her group is characterizing the microbial communities colonizing municipal landfills, with foci on methane cycling, bioplastics degradation, and community interactions. Dr. Hug’s work has been featured in major news outlets including the New York Times, the Atlantic, Discover Magazine, and on Public Radio International’s “The World”. She was a featured scientist on a TFO children’s show and the BBC Radio 4 program, “Bacteria, the tiny giants” in 2023.