Solving Challenges in Microalgae-Based Living Materials

Abstract

Engineered living materials (ELMs) integrate aspects of material science and biology into a unique platform, leading to materials and devices with features of life. Among those, ELMs containing microalgae have received increased attention due to the many benefits photosynthetic organisms provide. Due to their relatively recent occurrence, photosynthetic ELMs still face many challenges related to reliability, lifetime, scalability, and more, often based on the complicated crosstalk of cellular, material-based, and environmental variables in time. This Viewpoint aims to summarize potential avenues for improving ELMs, beginning with an emphasis on understanding the cell's perspective and the potential stresses imposed on them due to recurring flaws in many current ELMs. Potential solutions and their ease of implementation will be discussed, ranging from choice of organism, adjustments to the ELM design, to various genetic modification tools, so as to achieve ELMs with longer lifetime and improved functionality.

Keywords: Microalgae; engineered living materials; genetic modification; living hydrogel; photosynthesis; stress responses.

Figure 1

Representative functions of photosynthetic ELMs. When designing photosynthetic ELMs, the ability to fix CO₂ often represents the primary motivation. This can also be combined with other functions such as electricity generation, growth platforms, biosensing, or the creation of novel regenerative materials.

Figure 2

Challenges of ELMs: a complex communication of variables. Within an ELM, the phenotype of a cell (top left; lipid content, growth rate, etc.) is dependent on the environment into which an ELM is placed (top right; temperature, light, humidity, etc.). The perception and impact of environmental variables is moderated by design choices of the material (top middle; surface to volume ratio, water retention, etc.). The longer the duration, the more feedback occurs between cells, environment, and material (dashed arrows), potentially leading to new phenotypes. The genotype of the employed species with its inherent capacities and tolerance levels defines the type, onset, and scope of a phenotype (bottom left; lipid content, salinity tolerance, bioluminescence, etc.). The genotypes may also be expanded through genetic modification tools (bottom right; mutagenesis, genetic engineering, etc.). All these variables will influence the efficiency, reliability, lifetime, and thus the functionality of an ELM.