Growth, Distribution, and Photosynthesis of Chlamydomonas Reinhardtii in 3D Hydrogels

Living Porous Ceramics for Bacteria-Regulated Gas Sensing and Carbon Capture

Microorganisms hosted in abiotic structures have led to engineered living materials that can grow, sense, and adapt in ways that mimic biological systems. Although porous structures should favor colonization by microorganisms, they have not yet been exploited as abiotic scaffolds for the development of living materials. Here, porous ceramics are reported that are colonized by bacteria to form an engineered living material with self-regulated and genetically programmable carbon capture and gas-sensing functionalities. The carbon capture capability is achieved using wild-type photosynthetic cyanobacteria, whereas the gas-sensing function is generated utilizing genetically engineered E. coli. Hierarchical porous clay is used as a ceramic scaffold and evaluated in terms of bacterial growth, water uptake, and mechanical properties. Using state-of-the-art chemical analysis techniques, the ability of the living porous ceramics are demonstrated to capture CO2 directly from the air and to metabolically turn minute amounts of toxic gas into a benign scent detectable by humans.

Advanced bacteria-based biomaterials for environmental applications

A large amount of anthropogenic CO2 emissions are derived from Portland cement production, contributing to global warming, which threatens human health and exposes flora and fauna to ecological imbalance. With concerns about the high maintenance and repair costs of concrete, the development of microbially induced calcium carbonate precipitation (MICP)-based self-healing concrete has been extensively examined. Bacterial carriers for microcrack healing could enhance the concrete's self-healing capacity by maintaining bacterial activity and viability. To reduce cement consumption, the development of sustainable engineered living materials (ELMs) based on MICP has become a promising new research topic that combines synthetic biology and material science, and they can potentially serve as alternatives to traditional construction materials. This review aims to describe bacterial carriers and the ongoing development of advanced ELMs based on MICP. We also highlight the emerging issues linked to applying MICP technology at the commercial scale, including economic challenges and environmental concerns.

Multifunctional Biocomposite Materials from Chlorella vulgaris Microalgae

Extrusion 3D-printing of biopolymers and natural fiber-based biocomposites enables the fabrication of complex structures, ranging from implants' scaffolds to eco-friendly structural materials. However, conventional polymer extrusion requires high energy consumption to reduce viscosity, and natural fiber reinforcement often requires harsh chemical treatments to improve adhesion. We address these challenges by introducing a sustainable framework to fabricate natural biocomposites using Chlorella vulgaris microalgae as the matrix. Through bioink optimization and process refinement, we produced lightweight, multifunctional materials with hierarchical architectures. Infrared spectroscopy analysis reveals that hydrogen bonding plays a critical role in the binding and reinforcement of Chlorella cells by hydroxyethyl cellulose (HEC). As water content decreases, the hydrogen bonding network evolves from water-mediated interactions to direct hydrogen bonds between HEC and Chlorella, enhancing the mechanical properties. A controlled dehydration process maintains continuous microalgae morphology, preventing cracking. The resulting biocomposites exhibit a bending stiffness of 1.6 GPa and isotropic heat transfer and thermal conductivity of 0.10 W/mK at room temperature, demonstrating effective thermal insulation. These characteristics make Chlorella biocomposites promising candidates for applications requiring both structural performance and thermal insulation, offering a sustainable alternative to conventional materials in response to growing environmental demands.

Mechanically Tunable, Compostable, Healable and Scalable Engineered Living Materials

Advanced design strategies are essential to realize the full potential of engineered living materials, including their biodegradability, manufacturability, sustainability, and ability to tailor functional properties. Toward these goals, we present mechanically engineered living material with compostability, healability, and scalability - a material that integrates these features in the form of a stretchable plastic that is simultaneously flushable, compostable, and exhibits the characteristics of paper. This plastic/paper-like material is produced in scalable quantities (0.5-1 g L-1), directly from cultured bacterial biomass (40%) containing engineered curli protein nanofibers. The elongation at break (1-160%) and Young's modulus (6-450 MPa) is tuned to more than two orders of magnitude. By genetically encoded covalent crosslinking of curli nanofibers, we increase the Young's modulus by two times. The designed engineered living materials biodegrade completely in 15-75 days, while its mechanical properties are comparable to petrochemical plastics and thus may find use as compostable materials for primary packaging.

Controlled release of microorganisms from engineered living materials

Probiotics offer therapeutic benefits by modulating the local microbiome, the host immune response, and the proliferation of pathogens. Probiotics have the potential to treat complex diseases, but their persistence or colonization is required at the target site for effective treatment. Although probiotic persistence can be achieved by repeated delivery, no biomaterial that releases clinically relevant doses of metabolically active probiotics in a sustained manner has been previously described. Here, we encapsulate stiff probiotic microorganisms within relatively less stiff hydrogels and show a generic mechanism where these microorganisms proliferate and induce hydrogel fracture, resulting in microbial release. Importantly, this fracture-based mechanism leads to microorganism release with zero-order release kinetics. Using this mechanism, small (∼1 μL) engineered living materials (ELMs) release >10 8 colony-forming-units (CFUs) of E. coli in 2 h. This release is sustained for at least 10 days. Cell release can be varied by more than three orders of magnitude by varying initial cell loading and modulating the mechanical properties of encapsulating matrix. As the governing mechanism of microbial release is entirely mechanical, we demonstrate controlled release of model Gram-negative, Gram-positive, and fungal probiotics from multiple hydrogel matrices.

SIGNIFICANCE

Probiotics offer therapeutic benefits and have the potential to treat complex diseases, but their persistence at the target site is often required for effective treatment. Although probiotic persistence can be achieved by repeated delivery, no biomaterial that releases metabolically active probiotics in a sustained manner has been developed yet. This work demonstrates a generic mechanism where stiff probiotics encapsulated within relatively less stiff hydrogels proliferate and induce hydrogel fracture. This allows a zero-order release of probiotics which can be easily controlled by adjusting the properties of the encapsulating matrices. This generic mechanism is applicable for a wide range of probiotics with different synthetic matrices and has the potential to be used in the treatment of a broad range of diseases.

Printing Green: Microalgae-Based Materials for 3D Printing with Light

Microalgae have emerged as sustainable feedstocks due to their ability to fix CO2 during cultivation, rapid growth rates, and capability to produce a wide variety of metabolites. Several microalgae accumulate lipids in high concentrations, especially triglycerides, along with lipid-soluble, photoactive pigments such as chlorophylls and derivatives. Microalgae-derived triglycerides contain longer fatty acid chains with more double bonds on average than vegetable oils, allowing a higher degree of post-functionalization. Consequently, they are especially suitable as precursors for materials that can be used in 3D printing with light. This work presents the use of microalgae as "biofactories" to generate materials that can be further 3D printed in high resolution. Two taxonomically different strains -Odontella aurita (O. aurita, BEA0921B) and Tetraselmis striata (T. striata, BEA1102B)- are identified as suitable microalgae for this purpose. The extracts obtained from the microalgae (mainly triglycerides with chlorophyll derivatives) are functionalized with photopolymerizable groups and used directly as printable materials (inks) without the need for additional photoinitiators. The fabrication of complex 3D microstructures with sub-micron resolution is demonstrated. Notably, the 3D printed materials show biocompatibility. These findings open new possibilities for the next generation of sustainable, biobased, and biocompatible materials with great potential in life science applications.

Space-Efficient 3D Microalgae Farming with Optimized Resource Utilization for Regenerative Food

Photosynthetic microalgae produce valuable metabolites and are a source of sustainable food that supports life without compromising arable land. However, the light self-shading, excessive water supply, and insufficient space utilization in microalgae farming have limited its potential in the inland areas most in need of regenerative food solutions. Herein, this work develops a 3D polysaccharide-based hydrogel scaffold for vertically farming microalgae without needing liquid media. This liquid-free strategy is compatible with diverse microalgal species and enables the design of living microalgal frameworks with customizable architectures that enhance light and water utilization. This approach significantly increases microalgae yield per unit water consumption, with an 8.8-fold increase compared to traditional methods. Furthermore, the dehydrated hydrogels demonstrate a reduced size and weight (≈70% reduction), but readily recover their vitality upon rehydration. Importantly, valuable natural products can be produced in this system including proteins, carbohydrates, lipids, and carotenoids. This study streamlines microalgae regenerative farming for low-carbon biomanufacturing by minimizing light self-shading, relieving water supply, and reducing physical footprints, and democratizing access to efficient aquatic food production.

Dual carbon sequestration with photosynthetic living materials

Natural ecosystems offer efficient pathways for carbon sequestration, serving as a resilient approach to remove CO2 from the atmosphere with minimal environmental impact. However, the control of living systems outside of their native environments is often challenging. Here, we engineered a photosynthetic living material for dual CO2 sequestration by immobilizing photosynthetic microorganisms within a printable polymeric network. The carbon concentrating mechanism of the cyanobacteria enabled accumulation of CO2 within the cell, resulting in biomass production. Additionally, the metabolic production of OH- ions in the surrounding medium created an environment for the formation of insoluble carbonates via microbially-induced calcium carbonate precipitation (MICP). Digital design and fabrication of the living material ensured sufficient access to light and nutrient transport of the encapsulated cyanobacteria, which were essential for long-term viability (more than one year) as well as efficient photosynthesis and carbon sequestration. The photosynthetic living materials sequestered approximately 2.5 mg of CO2 per gram of hydrogel material over 30 days via dual carbon sequestration, with 2.2 ± 0.9 mg stored as insoluble carbonates. Over an extended incubation period of 400 days, the living materials sequestered 26 ± 7 mg of CO2 per gram of hydrogel material in the form of stable minerals. These findings highlight the potential of photosynthetic living materials for scalable carbon sequestration, carbon-neutral infrastructure, and green building materials. The simplicity of maintenance, coupled with its scalability nature, suggests broad applications of photosynthetic living materials as a complementary strategy to mitigate CO2 emissions.