Publications & Patents

• M.-Y. Lin, K.A. Severson, P. Grandgeorge, E. Roumeli, "Closed-Loop Optimization Using Machine Learning for the Accelerated Design of Sustainable Cements Incorporating Algal Biomatter" Matter (2025) Accepted. https://www.sciencedirect.com/science/article/pii/S2590238525003108 

Here we develop a new type of low-carbon cement by mixing in whole seaweed biomass, creating a more sustainable building material. Using a machine learning–guided design approach, we rapidly discover the optimal mix that meets compressive strength requirements while significantly reducing environmental impact—all in a fraction of the time traditional methods would take. Unlike conventional approaches that rely on processed additives, our method maximizes environmental benefit by using minimally processed biomass and integrating life cycle assessment (LCA) directly into the optimization workflow. Due to the complex and nonlinear hydration behavior of seaweed-cement composites, traditional models fall short in predicting strength evolution. By employing an amortized Gaussian process model with early stopping, we reduced the optimization cycle from years to just 28 days, using only 24 training formulations. The resulting material meets structural strength requirements while reducing global warming potential by 21%. 

• Lou, B., Parker, M., & Roumeli, E. "Effects of Pyrolysis Temperature of Macroalgal Biomass on the Structure and Mechanical Properties of Produced Biochar." BioResources (2025). DOI: 10.15376/biores.20.2.4152-4173

We explore the effect of pyrolysis temperature and oxidative pretreatment on resulting structure and properties of biochar derived from two types of macroalgae. Our publication demonstrates that thermal treatment can tailor carbon content, surface chemistry, and mechanical properties of algal biochars. Ulva and Sargassum are viable biochar feedstocks, with carbon retention and mechanical behavior strongly influenced by feedstock type, pretreatment temperature, and pyrolysis conditions; these biochars can be explored further for applications in soil amendments, filtration media, energy storage, and general environmental remediation technologies.

• G. Balistreri, I.R. Campbell, X. Li, J. Amorim, S. Zhang, E. Nance, and E. Roumeli. “Bacterial cellulose nanoparticles as a sustainable drug delivery platform for protein-based therapeutics.” RSC Applied Polymers (2024). DOI: 10.1039/D3LP00184A

Bacterial cellulose nanoparticles (BCNPs) can serve as an eco-friendly nanomedicine platform, offering a sustainable solution for drug delivery. We developed BCNPs from kombucha-cultured bacterial cellulose fibers, and examined their predominantly amorphous structure and efficient drug loading capabilities, demonstrated with bovine serum albumin as a model drug. BCNPs can potentially combine scalability and reduced waste in nanotherapeutic manufacturing.

• H. Iyer, A. Mandal, M. Holden, E. Roumeli "Modifying Bacterial Cellulose Dispersions with Deep Eutectic Solvent and Pectin to Tune the Properties of Open-Celled Foams"
  RSC Applied Polymers  (2024). DOI: 10.1039/D4LP00348A

Understanding the interactions between bacterial cellulose and pectin gels enables the tuning of the properties of cellulose/pectin foams, highlighting the potential for sustainable, biodegradable materials to compete with petroleum-based materials.

• I. Campbell, Z. Dong, P. Grandgeorge, A. M. Jimenez, E. Rhodes, E. Lee, S. Edmundson, C. Subban, K. Sprenger, E. Roumeli "The role of biomolecular building blocks on the cohesion of biomatter plastics"
  Matter  (2024). DOI: 10.1016/j.matt.2024.101941

In this study we investigate the molecular mechanisms responsible for cohesion in bioplastics made from algal biomatter. Because traditional chemical analyses are confounded by the molecular complexity of algae, we develop analogs for biomatter plastics by combining pure representatives of different classes of macromolecules (carbohydrates, lipids, and proteins). Analog composites are prepared using the same technique as algal bioplastics and their morphology, mechanical performance, and chemical bonding are evaluated. By varying the concentration of different macromolecules, the roles or effects of different molecules in/on the cohesion and mechanical performance were determined. In this work we were fortunate enough to collaborate with Dr. K. Sprenger and her group at the CU Boulder. They developed molecular dynamics models of biomatter analogues to complement experimental models and evaluate changing hydrogen bonding and protein secondary structures. Together, the computational and physical models suggest that inter/intra-molecular hydrogen bonding and protein aggregation facilitate cohesion in algal bioplastics.

• J. Amorim, K. Liao, A. Mandal, A. F. S. Costa, E. Roumeli, L. A. Sarubbo "Impact of Carbon Source on Bacterial Cellulose Network Architecture and Prolonged Lidocaine Release"
  Polymers (2024). DOI: 10.3390/polym16213021

In this study, we explore the influence of five carbon sources: raffinose, sucrose, glucose, arabinose, and glycerol, on bacterial cellulose (BC) production by Komagataeibacter hansenii. The selection of carbon source significantly affected BC yield, fiber morphology, and network properties, as evaluated through optical density and pH monitoring, SEM imaging, and WAXS analysis. BC pellicles were further processed into freeze-dried foams to preserve their natural porous structure, facilitating drug delivery applications. The foams were loaded with 5% lidocaine hydrochloride and demonstrated a sustained release profile over 14 days in simulated body fluid, with glycerol-grown BC exhibiting the highest cumulative release. Our findings provide insights into the role of carbon source selection in tailoring BC’s structural and functional properties for biomedical applications. This study also highlights BC’s versatility and sustainability as a platform for advanced wound care and drug delivery, offering new possibilities for the development of bioengineered therapeutic materials.

• A. Mandal, K. Liao, H. Iyer, J. Lin, X. Li, S. Zhang, E. Roumeli "Insights into controlling bacterial cellulose nanofiber film properties through balancing thermodynamic interactions and colloidal dynamics" Molecular Systems Design & Engineering  (2024). DOI: 10.1557/10.1039/D4ME00058G

This study investigates the dispersion of cellulose nanofibers (CNFs) produced by a bacterial–yeast co-culture, highlighting the pivotal role of thermodynamic interactions in influencing their colloidal behavior. By adjusting Hansen solubility parameters, we tuned the relationship between CNFs and solvents across various concentrations. Rheological measurements, small-angle X-ray scattering, and zeta potential analyses revealed that enhancing CNF–solvent interactions increases excluded volume in the dilute regime. This emphasizes the critical balance between fiber–fiber and fiber–solvent interactions. Additionally, we explored the transition from colloidal to solid state by creating films from dispersions with varying interaction parameters in semi-dilute regimes, showing that higher electrokinetic stabilization leads to stronger and tougher films. Our work offers an understanding of the thermodynamic and electrokinetic interplay that governs bacterial CNF dispersion, paving the way for future applications and a deeper understanding of nanocellulose's structure-property relationships.

• P. Grandgeorge, I. Campbell, H. Nguyen, R. Brain, M. Parker, S. Edmundson, D. Rose, K. Homolke, C. Subban, E. Roumeli "Adhesion in Thermo-Mechanically Processed Seaweed-Lignocellulosic Composite Materials" MRS Bulletin  (2024). DOI: 10.1557/s43577-024-00734-5

This work introduces Ulva seaweed as a sustainable adhesive alternative for wood-based composites. Current wood panels, such as medium density fiberboards (MDF), use formaldehyde-based resins to bond wood fibers and to provide strength and moisture protection. However, these resins are being critically examined due to detrimental environmental factors such as toxicity at high temperatures and petrochemical origins. Presently, upon hot-pressing, powdered Ulva flows in between wood particles, generating a matrix which provides strong binding. We show that the flexural strength of Ulva-bonded wood biocomposites increases with increasing Ulva concentrations. We perform infrared and x-ray photoelectron spectroscopy and identify indications of fatty acid mobility during hot-pressing. And lastly, we discuss additional biocomposite considerations such as water resistance, flame retardancy, and environmental impact.

• H. Iyer, P. Grandgeorge, A. M. Jimenez, I. Campbell, M. Parker, M. Holden, M. Venkatesh, M. Nelsen, B. Nguyen, E. Roumeli "Fabricating Strong and Stiff Bioplastics from Whole Spirulina Cells"
  Advanced Functional Materials  (2023) 2302067. DOI: 10.1002/adfm.202302067

In this paper, we introduce the concept of fabricating thermoformable bioplastics directly from unprocessed biological matter (biomatter). Specifically we show that spirulina, an abundant and photosynthetic cyanobacterium (also referred to as microalgae due to its photosynthetic activity) can be processed with conventional plastics manufacturing methods like extrusion and hot-pressing. The formed plastics have mechanical properties similar to other bioplastics like PLA, but also conventional petroleum-derived plastics like polystyrene. The generated bioplastics are reprocessable which opens up pathways for their mechanical recycling, and as they are composed of only biological matter, they are degradable in soil without requiring special incubation conditions. 

• M.-Y. Lin, P. Grandgeorge, A. M. Jimenez, B. H. Nguyen, E. Roumeli, "Long-Term Hindrance Effects of Algal Biomatter on the Hydration Reactions of Ordinary Portland Cement"
  ACS Sustainable Chemistry & Engineering, 2023, 11, 22, 8242–8254. DOI: 10.1021/acssuschemeng.2c07539

In this paper, we evaluate the effects of chlorella and spirulina, two abundant and photosynthetic microorganisms as fillers in cement, aiming to use them as means to reduce the carbon footprint of cement. Our results show that both types of biological matter interfere with the hyration reactions of cement, even at concentrations as low as 5 wt% which lead to a strength reduction of more than 80% after 91 days of curing. Both biomatters hinder the hydration reactions of calcium silicates, preventing the formation of calcium hydroxide and calcium silicate hydrate, while the secondary reactions of tricalcium aluminate that form ettringite are not affected. Our results provide fundamental insights into the mechanisms that govern the introduction of two carbon-negative species as fillers in cement, which are crucial for enabling strategies to overcome the detrimental effects that those fillers have on the mechanical properties of cement.

• I. Campbell, M. Lin, H. Iyer, M. Parker, J. L. Fredricks, K. Liao, A. M. Jimenez, P. Grandgeorge, E. Roumeli "Progress in sustainable polymers from biological matter"
  Annual reviews, (2023)  Vol 53:81-104. DOI: 10.1146/annurev-matsci-080921-083655

In this review, we cover recent advances in developing sustainable polymers from biological matter (biomatter), including progress in the extraction and utilization of bio-derived monomers and polymers, as well as the emergence of polymers produced directly from unprocessed biomatter (entire cells or tissues). We also discuss applications of sustainable polymers in bioplastics, biocomposites, and cementitious biomaterials, with emphasis on relating their performance to underlying fundamental mechanisms. Finally, we provide a future outlook for sustainable material development, highlighting the need for more accurate and accessible tools for assessing the life-cycle impacts and socioeconomic challenges as this field advances.

• J. L. Fredricks, A. M. Jimenez, P. Grandgeorge, R. Meidl, E. Law, J. Fan, E. Roumeli, "Hierarchical biopolymer-based materials and composites"
  Journal of Polymer Science, in press (2023).

In this review, we analyze the structural and mechanical properties of three of the most studied biopolymer classes: cellulose, chitin, and protein beta-sheet structures. We first discuss the hierarchical structure of the biopolymers and how their rich interaction networks induce appealing mechanical properties. Then, we review different fabrication and processing methods to translate these attractive properties into macroscopic materials and composites. Finally, we discuss a nascent approach which leverages the direct use of microorganisms, in the form of intact cells, tissues or dissociated biological matter (biomatter), as meso-scale material building blocks. These non- or little pre-processed biomatter building blocks are composed of the biopolymer structural elements (molecular-nano scale), but also inherit the higher-scale hierarchical characteristics. Processing-structure-property relationships for biomatter-based materials are discussed, emphasizing on the role of hierarchical arrangement, processing-induced transformations, and intermolecular bonding, on the macroscopic mechanical properties. Finally, we present a perspective on the role of biopolymers in a circular economy.

• K. Liao, P. Grandgeorge, A. M. Jimenez, B. H. Nguyen, E. Roumeli, "Effects of mechanical cell disruption on the morphology and properties of spirulina-PLA biocomposites"
  Sustainable Materials and Technologies (2023) https://doi.org/10.1016/j.susmat.2023.e00591

In this paper, we introduce a novel set of biocomposite materials obtained by compounding polylactic acid (PLA), one of the most consumed industrially degradable plastics, with spirulina, an abundant and fast-growing microalgal species serving as a filler. Specifically, we study the effect of using spirulina in a raw or physically dissociated form after Sonication. We find that independently of the filler pretreatment, the Young's modulus remains as high as neat PLA, while the elongation to break, strength, and toughness progressively decrease with increasing spirulina content. We show that the use of dissociated spirulina enhances the tensile strength by up to 25% compared to biocomposites made with unprocessed spirulina, as a result of the improved filler dispersion and reduced particle size. Our findings also reveal drastically enhanced moisture-induced plasticization in the biocomposites with dissociated spirulina. We report a remarkable 90% toughness increase with mechanically pretreated spirulina at a concentration of 9.1 wt% when compared to the non-water plasticized biocomposite at the same filler concentration, even rivaling the toughness of neat PLA. Finally, we provide estimates for the reduced global warming potential of the produced biocomposites, as compared to neat PLA. Our study presents a holistic view of the performance of PLA-spirulina biocomposites and demonstrates the effectiveness of physical filler dissociation as a means to improve the strength and toughness of the biocomposites. 

• J. Fredricks, M. Parker, P. Grandgeorge, A. M. Jimenez, E. Law, M. Nelsen, E. Roumeli, "The effects of temperature, pressure, and time on lignin incorporation"
  MRS Communications (2022) https://doi.org/10.1557/s43579-022-00191-8

Due to the increasing detrimental impacts of mass non-renewable plastics over the last decades, cellulose-based materials have been extensively studied as a promising sustainable alternative. Here, we prepare lignocellulosic papers (LBC) from bacterial cellulose (BC) impregnated with lignin, and analyze their mechanical properties, microstructure, and wetting kinetics. We follow a design of experiment analysis to obtain the optimal pressing conditions of the BC and LBC papers, targeted at maximizing the specific ultimate tensile strength and toughness. At optimal conditions, lignin impregnation enhances the absolute modulus, strength, and toughness of BC by 108%, 142%, and 63%, respectively.

• E. Roumeli, R. Hendrickx, L. Bonanomi, A. Vashisth, K. Rinaldi, C. Daraio "Biological matrix composites from cultured plant cells"
  PNAS 119 (15) e2119523119 (2022). DOI: https://doi.org/10.1073/pnas.2119523119 

In this paper, we introduce the idea of using entire cultured plant cells as a polymer composite building block to fabricate self-bonded bulk materials with properties similar to commodity plastics. The matrix formed by compacted plant cells is held together through the native biopolymer chain interactions, thus eliminating the need for binders. Since we use the entire plant cell, the process creates no waste and does not require the use of arable land. In addition, we show that the produced materials can biodegrade fast when buried in soil without requiring extra heat, pressure, or added microorganisms to assist the process. Finally we demonstrate that the achieved properties can be enhanced by the introduction of filler particles, which would expand the possible applications of our biological matrix materials.

• L. Ginsberg, R. McDonald, Q. Lin, R. Hendrickx, G. Spigolon, G. Ravichandran, C. Daraio, E. Roumeli. "Cell wall and cytoskeletal contributions in single cell biomechanics of Nicotiana tabacum" Quantitative Plant Biology 3 (2022). DOI: https://doi.org/10.1017/qpb.2021.15 

This paper studies the contributions of the CW, microtubules (MTs) and actin filaments (AFs), in the mechanical properties of Nicotiana tabacum cells. To compare measurements obtained by atomic force microscopy and micro-indentation tests, we develop two generative statistical models to describe the cell’s behaviour using one or both datasets. Our results illustrate that MTs and AFs contribute significantly to cell stiffness and dissipated energy, while confirming the dominant role of turgor pressure.

• J. L. Fredricks, H. Iyer, R. McDonald, J. Hsu, A. M. Jimenez, E. Roumeli, "Spirulina-based composites for 3D-printing", Journal of Polymer Science, (2021). https://doi.org/10.1002/pol.20210683

In this paper we develop and characterize materials for cold extrusion-based 3D-printing comprised of unprocessed spirulina and varying amounts of cellulose fibers (CFs). Tuning the micro-morphology, density, and mechanical properties of multilayered structures is achieved by modulating the CF amount or drying method. 

• E. Roumeli, L. Ginsberg, R. McDonald, G. Spigolon, R. Hendrickx, M. Ohtani, T. Demura, G. Ravichandran, C. Daraio, "Structure and Biomechanics during Xylem Vessel Transdifferentiation in Arabidopsis thaliana", Plants 9 (2020), 1715. doi:10.3390/plants9121715. 

In this paper, we study the structure and biomechanics of cultured plant cells during the cellular developmental stages associated with SCW formation. We use a model culture system that induces transdifferentiation of Arabidopsis thaliana cells to xylem vessel elements, upon treatment with dexamethasone (DEX). We group the transdifferentiation process into three distinct stages, based on morphological observations of the cell walls. The first stage includes cells with only a primary cell wall (PCW), the second covers cells that have formed a SCW, and the third stage includes cells with a ruptured tonoplast and partially or fully degraded PCW. We adopt a multi-scale approach to study the mechanical properties of cells in these three stages. We perform large-scale indentations with a micro-compression system in three different osmotic conditions. Atomic force microscopy (AFM) nanoscale indentations in water allow us to isolate the cell wall response. We propose a spring-based model to deconvolve the competing stiffness contributions from turgor pressure, PCW, SCW and cytoplasm in the stiffness of differentiating cells. Prior to triggering differentiation, cells in hypotonic pressure conditions are significantly stiffer than cells in isotonic or hypertonic conditions, highlighting the dominant role of turgor pressure. Plasmolyzed cells with a SCW reach similar levels of stiffness as cells with maximum turgor pressure. The stiffness of the PCW in all of these conditions is lower than the stiffness of the fully-formed SCW. Our results provide the first experimental characterization of the mechanics of SCW formation at single cell level.