3D printed live yeast cells enable more efficient ethanol production

Scientists at the Lawrence Livermore National Laboratory (LLNL) have demonstrated the ability to 3D print live yeast cells that convert glucose to ethanol and carbon dioxide gas (CO2), resulting in a substance similar to beer. The recent breakthrough showcases the potential to use bioprinting for applications that require biocatalytic processes.

Though many of the bioprinting research efforts that we cover are centered on 3D printing living mammalian cells, scientists are also exploring the ability to bioprint functional microbes that act as biocatalysts, inducing chemical transformations in organic compounds. This branch of research could have applications in the food industry, biofuel production, waste treatment and bioremediation, where live microbes are used to convert carbon sources into valuable end-product chemicals.

The recent research conducted at LLNL—recently published in the journal Nano Letters—has shown that it is possible to bioprint live whole-cells to assist in understanding microbial behaviours, communication and interactions with the microenvironment and to develop new bioreactors with high volumetric productivity.

In their demonstration, the researchers 3D printed freeze-fried live biocatalytic yeast cells (Saccharomyces cerevisiae) into a porous scaffold structure. The geometry of the structure enabled the yeast cells to efficiently convert glucose to ethanol and CO2—not unlike how beer is made.

Notably, the researchers used a new bioink substance which results in self-supporting structures that are high resolution and have tunable cell densities, large-scale, high-catalytic activity and long-term viability.

“Compared to bulk film counterparts, printed lattices with thin filament and macro-pores allowed us to achieve rapid mass-transfer leading to several-fold increase in ethanol production,” explained Fang Qian, a materials scientist at LLNL and the lead and corresponding author on the paper. “Our ink system can be applied to a variety of other catalytic microbes to address broad application needs. The bioprinted 3D geometries developed in this work could serve as a versatile platform for process intensification of an array of bioconversion processes using diverse microbial biocatalysts for production of high-value products or bioremediation applications.”

The LLNL bioprinting project can be seen as an early step in the use of bioprinting for genetically modified yeast cells which have applications in producing high-valuable pharmaceuticals, chemicals, food and biofuels.

“There are several benefits to immobilizing biocatalysts, including allowing continuous conversion processes and simplifying product purification,” added chemist Sarah  Baker, the other corresponding author on the paper. “This technology gives control over cell density, placement and structure in a living material. The ability to tune these properties can be used to improve production rates and yields. Furthermore, materials containing such high cell densities may take on new, unexplored beneficial properties because the cells comprise a large fraction of the materials.”

“This is the first demonstration for 3D printing immobilized live cells to create chemical reactors,” concluded engineer Eric Duoss, a co-author on the paper. “This approach promises to make ethanol production faster, cheaper, cleaner and more efficient. Now we are extending the concept by exploring other reactions, including combining printed microbes with more traditional chemical reactors to create ‘hybrid’ or ‘tandem’ systems that unlock new possibilities.”