Biological systems assemble tissues and structures with advanced properties in ways that cannot be achieved by man-made materials. Living materials self-assemble under mild conditions, are autonomously patterned, can self-repair and sense and respond to their environment. Inspired by this, the field of engineered living materials (ELMs) aims to use genetically-engineered organisms to generate novel materials. Bacterial cellulose (BC) is a biological material with impressive physical properties and low cost of production that is an attractive substrate for ELMs. Inspired by how plants build materials from tissues with specialist cells we here developed a system for making novel BCbased ELMs by addition of engineered yeast programmed to add functional traits to a cellulose matrix. This is achieved via a synthetic 'symbiotic culture of bacteria and yeast' (Syn-SCOBY) approach that uses a stable co-culture of Saccharomyces cerevisiae with BC-producing Komagataeibacter rhaeticus bacetria. Our Syn-SCOBY approach allows inoculation of engineered cells into simple growth media, and under mild conditions materials self-assemble with genetically-programmable functional properties in days. We show that co-cultured yeast can be engineered to secrete enzymes into BC, generating autonomously grown catalytic materials and enabling DNA-encoded modification of BC bulk material properties. We further developed a method for incorporating S. cerevisiae within the growing cellulose matrix, creating living materials that can sense chemical and optical inputs. This enabled growth of living sensor materials that can detect and respond to environmental pollutants, as well as living films that grow images based on projected patterns. This novel and robust Syn-SCOBY system empowers the sustainable production of BC-based ELMs..
Our demand for electronic goods and fossil fuels have challenged our ecosystem with contaminating amounts of heavy metals causing numerous water sources to become polluted. To counter heavy metal waste industry has relied on a family of physicochemical processes with chemical precipitation being one of the most commonly used. However, the disadvantages of chemical precipitation are vast, some of which are the generation of secondary waste, technical handling of chemicals, and need for complex infrastructures. To circumvent these limitations, biological processes have been sought after to naturally manage waste. Here, we show that yeast can act as a biological alternative to traditional chemical precipitation by controlling naturally occurring production of hydrogen sulfide (H2S). Sulfide production was harnessed by controlling the sulfate assimilation pathway, where strategic knockouts and culture conditions generated H2S from 0 to over 1000 ppm (~30 mM). These sulfide-producing yeasts were able to remove mercury, lead, and copper from real-world samples taken from the Athabasca Oil Sands. More
Biological systems assemble tissues and structures with advanced properties in ways that cannot be achieved by man-made materials. Living materials self-assemble under mild conditions, are autonomously patterned, can self-repair and sense and respond to their environment. Inspired by this, the field of engineered living materials (ELMs) aims to use genetically-engineered organisms to generate novel materials. Bacterial cellulose (BC) is a biological material with impressive physical properties and low cost of production that is an attractive substrate for ELMs. Inspired by how plants build materials from tissues with specialist cells we here developed a system for making novel BCbased ELMs by addition of engineered yeast programmed to add functional traits to a cellulose matrix. This is achieved via a synthetic 'symbiotic culture of bacteria and yeast' (Syn-SCOBY) approach that uses a stable co-culture of Saccharomyces cerevisiae with BC-producing Komagataeibacter rhaeticus bacetria. Our Syn-SCOBY approach allows inoculation of engineered cells into simple growth media, and under mild conditions materials self-assemble with genetically-programmable functional properties in days. We show that co-cultured yeast can be engineered to secrete enzymes into BC, generating autonomously grown catalytic materials and enabling DNA-encoded modification of BC bulk material properties. We further developed a method for incorporating S. cerevisiae within the growing cellulose matrix, creating living materials that can sense chemical and optical inputs. This enabled growth of living sensor materials that can detect and respond to environmental pollutants, as well as living films that grow images based on projected patterns. This novel and robust Syn-SCOBY system empowers the sustainable production of BC-based ELMs.
Hyperaccumulators typically refer to plants that absorb and tolerate elevated amounts of heavy metals. Due to their unique metal trafficking abilities, hyperaccumulators are promising candidates for bioremediation applications. However, compared to bacteria-based bioremediation systems, plant life cycle is long and growing conditions are difficult to maintain hindering their adoption. Herein, we combine the robust growth and engineerability of bacteria with the unique waste management mechanisms of plants by using a more tractable platform-the common baker’s yeast-to create plant-like hyperaccumulators. Through overexpression of metal transporters and engineering metal trafficking pathways, engineered yeast strains are able to sequester metals at concentrations 10–100 times more than established hyperaccumulator thresholds for chromium, arsenic, and cadmium. Strains are further engineered to be selective for either cadmium or strontium removal, specifically for radioactive Sr90. Overall, this work presents a systematic approach for transforming yeast into metal hyperaccumulators that are as effective as their plant counterparts.
BackgroundIn the therapeutic antibody development process, the yeast display technology which expresses a large library of antibodies is very useful for increasing the affinity of a lead antibody. Ideally, a yeast library should exceed the size of 10E10 to 10E11 to get close to the real affinity maturation process. However, due to low transformation efficiency with yeast, it requires trememdous scaling-up efforts to simply reach the 10E9 library size.MethodsTo address the transformation problem, we developed a new electroporation device that applies a high voltage on a sealed electroporation tube containing the yeast and plasmids in a low conductance buffer.ResultsThe new device is arcing free due to the sealed design and each single reaction could generate 10E8 library size, far exceeding the 10E6 size that was previously reported in a single reaction.ConclusionsWith the improved transformation efficiency, it becomes very straightforward to reach the currently difficult size of 10E9. Further more, it is possible to reach the 10E10 to 10E11 library size with reaction scaling-up. Our new method could be very useful for the field of antibody development.
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