Randy Lewis

Randy Lewis
Brigham Young University - Provo Main Campus | BYU · Department of Chemical Engineering

About

86
Publications
21,860
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2,359
Citations
Citations since 2017
9 Research Items
819 Citations
2017201820192020202120222023020406080100120140
2017201820192020202120222023020406080100120140
2017201820192020202120222023020406080100120140
2017201820192020202120222023020406080100120140

Publications

Publications (86)
Article
Full-text available
Hazards associated with air pollution motivate the search for technologies capable of monitoring individual exposure to gaseous pollutants and particle matter (PM). A Low-cost Optical Particle Counter (OPC), costing less than 50 USD, is an example of such technologies. Currently, OPCs are widely used to measure the concentration of PM in ambient ai...
Article
The MoFe protein component of the nitrogenase enzyme complex is the substrate reducing site and contains two sets of symmetrically arrayed metallo centers called the P (Fe8S7) and the FeMoco (MoFe7S9-C-homocitrate) centers. The ATP-binding Fe protein is the specific reductant for the MoFe protein. Both symmetrical halves of the MoFe protein are tho...
Article
Biomass cookstoves have been studied extensively for several decades. The Water Boiling Test (WBT) has been a widely adopted protocol for obtaining measurements needed to quantify biomass cookstove performance metrics. WBT metrics have been commonly used to evaluate cookstove effectiveness and serve as a basis for comparing biomass cookstoves. This...
Article
Syngas fermentation for producing biofuels and other products suffers from mass transfer limitations due to low CO and H2 solubility in liquid medium. Therefore, it is critical to characterize mass transfer rates of these gases to guide bioreactor design and optimization. This work presents a novel technique to measure the volumetric mass transfer...
Article
Full-text available
A trickle-bed reactor (TBR) when operated in a trickle flow regime reduces liquid resistance to mass transfer because a very thin liquid film is in contact with the gas phase and results in improved gas–liquid mass transfer compared to continuous stirred tank reactors (CSTRs). In the present study, continuous syngas fermentation was performed in a...
Article
Many individuals in developing areas use biomass cookstoves for cooking although there are many inherent health hazards. Judging which improved cookstove to use and distinguishing the best one for a given cooking style to mitigate these hazards is challenging. Thermal efficiency (ηth) is one assessment parameter of cookstoves that is often used. To...
Conference Paper
Full-text available
International educational opportunities for engineering students include, but are not limited to, internships, study abroad programs, and humanitarian programs such as Engineers Without Borders. Since 2007, a two-semester Global Engineering Outreach course at Brigham University has enabled engineering and technology students from multiple disciplin...
Conference Paper
The Water Boiling Test (WBT) is one of the most common methods used for analyzing biomass cookstoves. For example, thermal efficiency, time to boil, and emissions metrics are assessed. These metrics are used as part of cookstove development including informing decisions about the suitability of cookstoves for dissemination. As these metrics have be...
Article
Biomass cookstoves are used by many people throughout the developing world for daily cooking, which unfortunately brings inherent risks to individuals and the environment. During the past several decades, extensive efforts have been made to mitigate the harm by developing clean burning, high efficiency biomass cookstoves. However, comparison and se...
Article
Full-text available
An efficient syngas fermentation bioreactor provides a mass transfer capability that matches the intrinsic kinetics of the microorganism to obtain high gas conversion efficiency and productivity. In this study, mass transfer and gas utilization efficiencies of a trickle bed reactor during syngas fermentation by Clostridium ragsdalei were evaluated...
Article
A two-semester multi-disciplinary Global Engineering Outreach (GEO) course was initiated in 2007 to provide an opportunity for junior and senior-level engineering and technology students to design and implement humanitarian-based engineering projects in developing communities. Recently, the course was integrated with a sociology course to enhance t...
Article
Biomass cookstoves are used extensively throughout the developing world. Many improved cookstoves are being developed to minimize health hazards, maximize efficiency, and reduce fuel consumption. Commonly, cookstoves have been assessed using the Water Boiling Test (WBT), the Controlled Cooking Test (CCT), the Kitchen Performance Test (KTP), and com...
Article
This paper presents the results of an investigation of the impact of co-firing a traditional Peruvian biomass cookstove with biogas on emissions and on combustion efficiency. The impact of using a fan to increase the airflow into the combustion zone with was also assessed. The cookstove was tested (1) without co-firing and without the fan, (2) with...
Conference Paper
The hybrid gasification and syngas-fermentation technology can be used in sustainable production of fuels and chemicals from biomass and wastes via gaseous feedstocks. The low solubility of CO and H2 in the liquid medium makes mass transfer a major challenge for this technology. Gas fermentation reactors designed to provide mass transfer capacity t...
Article
Methyl viologen (MV) is an electron mediator that has been shown to be beneficial for enhancing product formation in biofuel processes. For example, increased yields have been observed for ethanol and butanol production. MV has also been used in bioremediation processes such as removal of pollutants from groundwater. However, MV has also been shown...
Conference Paper
Synthesis gas (syngas) fermentation involves the conversion of CO and H2 to alcohols, organic acids and other chemicals using acetogens. A major challenge for advancing syngas fermentation is the mass transfer limitation associated with low solubility of CO and H2 in the fermentation broth. An efficient syngas fermentation reactor should provide a...
Conference Paper
Biofuel production via fermentation is produced primarily by fermentation of simple sugars. Besides the sugar fermentation route, there exists a promising alternative process that uses syngas (CO, H2, CO2) produced from biomass as building blocks for biofuels. Although syngas fermentation has many benefits, there are several challenges that still n...
Article
Producing biofuels from gasified biomass (synthesis gas) via microbial fermentation is currently being pursued as one alternative in biofuels development. In synthesis gas fermentation, reducing equivalents from H2 oxidation via hydrogenase is important towards directing more carbon towards product formation. In this work, kinetic studies of H2 uti...
Article
Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H(2) to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. Th...
Article
Full-text available
Current design methods such as appropriate technology, human-centered design, and participatory design are intended to generate development projects that resonate with users in communities in developing countries. These approaches are extremely useful, but often lack adequate documentation about how to collect data on and incorporate users feedback...
Conference Paper
Ethanol can be produced from biomass feedstocks or municipal solid wastes (MSW) using a hybrid thermochemical-biochemical conversion process called gasification-fermentation. In the gasification-fermentation process, biomass is gasified and converted to synthesis gas (syngas; primarily CO, CO2 and H2). The advantage of gasification-fermentation ove...
Article
Hydrogenase activity plays an important role in the fermentation of biomass-generated syngas (containing CO, CO2, and H2) to obtain ethanol and other biofuels. One process efficiency issue for producing biofuels from syngas fermentation is the ability of key cellular enzymes to produce reducing equivalents from syngas. For microbes using the Wood–L...
Article
With the advancement of post-gasification processing, evaluating the effect of gas composition on ethanol production becomes important, as the composition could be shifted prior to fermentation to optimize ethanol yield. Increasing the overall efficiency of syngas conversion to bio-ethanol involves optimizing the use of the hydrogen (H2) component...
Conference Paper
Syngas fermentation involves complex biochemical reactions of gaseous substrates to produce liquid products such as ethanol, butanol and acetic acid using special group of acetogenic microorganisms. Ethanol productivity and syngas conversion efficiency are severely affected by the low solubility of CO and H2, the primary components of syngas, in th...
Conference Paper
Many fermentation processes have been used to convert biomass to various fuels. Syngas, which is a mixture of CO, CO2, and H2, is one process being studied for the production of ethanol. Per mole of ethanol produced, 12 electrons are consumed. H2 and CO are the electron sources in syngas fermentation. One issue involved in syngas fermentation is th...
Conference Paper
Ethanol has emerged as a promising alternative to fossil fuels. Ethanol is produced primarily through two different processes. The first process produces ethanol by fermentation of simple sugars. The second process uses syngas (H2, CO, and CO2) produced from gasification of biomass. Many different reactors can be used for syngas fermentation. These...
Conference Paper
Hydrogen and carbon monoxide, sparingly soluble gases are transferred to reactive sites inside cells during fermentation of synthesis gas to fuel and chemicals. The rate of conversion is set by either the transfer of gas into the cell or the kinetics of reaction inside the cell. Gas consumption, cell growth and production of ethanol and acetic acid...
Conference Paper
Gasification of cellulosic biomass followed by the fermentation of the resulting syngas for the production of ethanol and other alcohols is a novel technology. Critical bottlenecks, such as low cell density and gas-liquid mass transfer limitations, diminish alcohol productivity, lower syngas conversion efficiency, and inhibit the movement of this p...
Article
Many biological processes have utilized the addition of sulfide constituents, such as sodium sulfide or cysteine-sulfide, to affect the redox potential, remove residual oxygen, and/or provide a source of sulfur for metabolism. However, the effects of sulfide constituents and associated sulfide concentrations on growth and product formation of cellu...
Article
The fermentation of syngas (CO, CO2, and H2) produced from biomass gasification for the production of ethanol has received increased attention due to the low cost and abundance of cellulosic feedstocks. Since CO plays a critical role in the available reducing equivalents and carbon conversion, this work assessed the effects of constant CO partial p...
Conference Paper
Many fermentation processes have been used to convert biomass to various fuels. Currently, the fermentation of syngas, which is a mixture of CO, CO2, and H2, is being studied for the production of ethanol. In our studies, an anaerobic microbial catalyst Clostridium P11 was used. The mass transfer rate, which is a function of the gas partial pressur...
Conference Paper
Volatile oil prices, insufficient domestic resources, and global depletion of fossil fuels have led to a need for alternative energy sources. Ethanol is one of the alternatives, with many advantages. It is renewable and carbon neutral, it can be produced domestically, and it has great potential for low-cost production. Despite the skepticism of e...
Article
Polyethylene terephthalate (PET) was functionalized to introduce carboxyl groups onto its surface by a carboxylation technique. Surface and bulk properties, such as possible surface deterioration, surface roughness and the mechanical strength of the carboxylated polymers, were studied and compared with those of aminolyzed and hydrolyzed PET. Atomic...
Conference Paper
Rising fuel prices, concern about long term crude oil supply, and increasing anthropogenic carbon dioxide emissions have increased motivation to find alternatives to traditional oil-derived transportation fuels. Among the most promising alternative fuels is ethanol, which in the United States is produced almost entirely from corn. The simple-sugar...
Conference Paper
Student chapters of Engineers Without Borders (EWB) are becoming increasingly popular in Engineering Colleges across the nation. The purpose of EWB is to improve the quality of life of developing communities throughout the world through the implementation of sustainable engineering projects, while training internationally responsible engineering st...
Conference Paper
Many fermentation processes have been used to convert biomass to various fuels. Currently, the fermentation of syngas, which is a mixture of CO, H2 and N2, is being studied for the production of ethanol. In our studies, an anaerobic microbial catalyst Clostridium carboxidivorans was used and the key performance parameters, such as growth rate and e...
Article
Developing low-cost sustainable fuels, such as ethanol, is receiving much attention due to rising energy costs, national security, and environmental issues. Renewable biomass, such as switchgrass, can be utilized to produce fuel-grade ethanol via a gasification and fermentation process. During the gasification process, biomass is converted to synga...
Article
Experiments involving enzymatic degradation of cellulose and dialysis of creatinine were introduced at Oklahoma State university (OSU) in the unit Operations Laboratory (UOL) to enhance biomedical/biochemical engineering opportunities in chemical engineering. These type of projects enhances the instructions that the students receive in optional Int...
Article
Full-text available
S-nitrosothiols (RSNOs) have many biological functions including platelet deactivation, immunosupression, neurotransmission, and host defense. Most of the functions are attributed to nitric oxide (NO) release during S-nitrosothiol decomposition. As the simplest biologically occurring S-nitrosothiol, S-nitrosocysteine (CySNO) has been widely used as...
Article
The production of renewable fuels, such as ethanol, has been steadily increasing owing to the need for a reduced dependency on fossil fuels. It was demonstrated previously that biomass-generated synthesis gas (biomass-syngas) can be converted to ethanol and acetic acid using a microbial catalyst. The biomass-syngas (primarily CO, CO(2), H(2), and N...
Article
Full-text available
The effective utilization of engineering principle in a model to predict the distance traveled by a Chem-E-Car using the acetic acid/baking soda reaction, is discussed. The model is specific for one type of car-propulsion system and demonstrates how engineering analysis is applicable to the Chem-E-Car competition. One could extend the engineering a...
Article
In our previous work, we demonstrated that biomass-generated producer gas can be converted to ethanol and acetic acid using a microbial catalyst Clostridium carboxidivorans P7T. Results showed that the producer gas (1) induced cell dormancy, (2) inhibited H2 consumption, and (3) affected the acetic acid/ethanol product distribution. Results of this...
Article
Thiol groups were attached to polyethylene terephthalate (PET) to promote the transfer of a known platelet inhibitor, nitric oxide (NO), from nitrosated thiols naturally found in the body to PET, followed by the release of NO from PET to prevent platelet adhesion. In order to immobilize the most thiols on the modified polymer, the processing parame...
Article
Recently, we reported that L-cysteine attached to polymeric biomaterials, without prior nitrosation, enhances the hemocompatibility of biomaterials via exploiting endogenous nitric oxide (NO). As part of the polymer optimization process to further enhance platelet inhibition, a kinetic model is being developed to predict the release rate of NO. A k...
Article
The development of low-cost, sustainable, and renewable energy sources has been a major focus since the 1970s. Fuel-grade ethanol is one energy source that has great potential for being generated from biomass. The demonstration of the fermentation of biomass-generated producer gas to ethanol is the major focus of this article in addition to assessi...
Article
Various aspects related to the incorporation of computational fluid dynamics (CFD) in a junior level chemical reaction engineering course at Oklahama State University are discussed. The students are taught to use CFD for predicting the single-reaction conversion of a species in a nonideal reactor. The last few weeks of the course are dedicated to t...
Article
As a small biological molecule, nitric oxide (NO), plays a key role in diverse functions including smooth muscle cell regulation, neurotransmission, inhibition of platelet aggregation, and cytotoxic actions. The assessment of NO effects in biological systems has extensively been studied using NO donor compounds that often have differing NO release...
Article
Full-text available
A recently discovered clostridial bacteria converts components of synthesis gas (CO, CO2, H2) into liquid products such as ethanol, butanol and acetic acid. Isolated from an agricultural lagoon, the stability and productivity characteristics of the bacteria were studied in a continuous bubble column bioreactor at 37°C using artificial blends of CO,...
Article
The survival of encapsulated pancreatic cells or islets is often limited because of nutrient deficiency, fibrotic overgrowth, and immune attack. Activated immune cells, such as macrophages, release nitric oxide (NO) and superoxide O 2- These species or their reactive intermediates, such as peroxynitrite, can be cytotoxic, mutagenic, and/or carcinog...
Article
Nitric oxide can be introduced slowly and steadily into aqueous solutions, including cell culture media, over extended periods of time via semipermeable Silastic (a registered trademark of the Dow Corning Corp.) polymer membranes. The rates of introduction are predictable and reproducible and can approach rates of nitric oxide production by stimula...
Article
A novel method for improving the haemocompatibility of biomedical materials through endogenous nitric oxide (NO) is presented. L-cysteine was covalently immobilized onto two biomedical polymers: polyurethane (PU) and polyethylene terephthalate (PET). The L-cysteine content on the polymers was approximately 5-8 nmol/cm2 as quantified via a chemilumi...
Article
Vascular thrombosis is regulated via the release of several constituents from the vascular endothelium, including nucleoside triphosphate diphosphohydrolases (NTPDases or ectonucleotidases), nitric oxide (NO), and eicosanoids. Currently, it is unknown how these constituents interact in the inhibition of platelet aggregation and adhesion. To investi...
Article
Nitric oxide (NO) is a physiological species involved in inhibition of platelet adhesion and aggregation. A novel NO delivery device was utilized to quantitatively assess the effects of gaseous NO on platelet deposition to agonist-coated biomaterials in the presence of a platelet suspension. Platelet deposition was evaluated as a function of agonis...
Article
Full-text available
The onset of insulin-dependent diabetes mellitus (IDDM) is often associated with the infiltration of pancreatic cells by macrophages. Upon activation, macrophages release nitric oxide (NO) and superoxide (O2). These species or their reactive intermediates can be cytoxic, mutagenic, or carcinogenic. Previous studies have reported both positive and n...
Article
Platelet adhesion and aggregation restrict the clinical applicability of blood-contacting biomaterials. Nitric oxide (NO) is a simple biological molecule that may be incorporated into biomaterials to inhibit platelet deposition. The toxicity of NO at superphysiological levels necessitates the determination of aqueous NO concentrations and fluxes th...
Article
Nitric oxide (NO), a recently discovered biological molecule synthesized by many cells, has many physiological roles including blood pressure regulation, neurotransmission, and inhibition of platelet adhesion. However, NO and reactive species formed in the presence of oxygen and superoxide can also be cytotoxic, mutagenic, or carcinogenic. Two nove...
Article
Nitric oxide (NO) is a simple biological molecule which inhibits adhesion and aggregation of platelets. A novel NO delivery device has been developed to quantitatively study the effects of NO concentration and flux on the adhesion of platelets to a surface. The slit-flow device is lined with a protein-coated membrane through which NO gas permeates...
Article
An accurate model of the nitric oxide (NO)-release rate is essential for predicting the temporal NO-release rate and resulting NO concentrations for NO donors. Knowledge of the NO-release rate and/or the NO concentration is beneficial for assessing the physiological or pathological effects of NO on cell systems. This study describes a method to mea...
Article
We have described a novel apparatus for studying the rates of certain reactions of NO in aqueous solutions. A principal feature of this system is the ability to continuously measure NO concentrations, by employing a membrane inlet in conjunction with a chemiluminescence detector. The design variables that influence the performance of such systems h...
Article
Full-text available
To investigate the fate of nitric oxide (NO) synthesized by activated macrophages, the concentrations of NO and its principal reaction products, nitrite (NO2) and nitrate (NO3), were measured as a function of time in suspension cultures of RAW264.7 macrophages attached to microcarrier beads. Synthesis of NO became evident 2-5 h after stimulation of...
Article
The kinetics of N-nitrosation in oxygenated nitric oxide (NO) solutions at physiological pH are important because of the cytotoxic, mutagenic, and carcinogenic effects of NO and its derivatives. N-nitrosation of morpholine in the presence of NO and O2 at pH 7.4 was investigated using a novel reactor in which NO, nitrite (NO2-), and N-nitrosomorphol...
Article
Full-text available
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1995. Includes bibliographical references (leaves 180-187). by Randy Stewart Lewis. Ph.D.
Article
An understanding of the rate of reaction of nitric oxide (NO) with oxygen in aqueous solutions is needed in assessing the various actions of NO in the body. A novel approach was developed for studying the kinetics of this reaction, which permitted simultaneous and continuous measurements of the concentrations of NO and the principal product, nitrit...
Article
Nitric oxide (NO) is an important physiological and biochemical messenger that may be involved in endogenous carcinogenesis and cell toxicity via formation of N-nitroso compounds or direct DNA damage by nitrosating agents arising from the reaction of NO with O2. To study the reaction of NO with O2 in model systems and the formation and disappearanc...

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Project (1)
Archived project
The goal of this project was to understand and improve the conversion of syngas to biofuels using an anaerobic clostridium.