Genetic Modification to Optimize the Adhesive Properties of Phototrophic Microbes for Environmental Biotechnology Applications


Cyanobacteria are photosynthetic microbes capable of converting solar energy into liquid biofuel like alkanes and ethanol and biofuel precursors like free fatty acids. They can be thought of as individual machines efficiently transforming sunlight and CO2 into fuel and like machines they can be engineered with new capabilities. Because they are bacteria they are relatively easy to genetically modify compared to plants and even other photosynthetic microbes like algae. Researchers at the Biodesign Institute of Arizona State University have made several innovations increasing both the quantity and quality of biofuel and biofuel precursors as well as engineering several features into the organism to help reduce the cost of product recovery. One of these features involves engineering cyanobacteria to autoagglutinate (clump) as a way to reduce the costs associated with dewatering typically an energy-intensive step in algae biofuel production. When the culture is ready to harvest CO2 aeration is discontinued which induces the expression of a gene that changes the cyanobacterial cell surface in such a way that cells stick to each other and precipitate out of solution. The concentrated biomass can then be collected and the biofuel extracted using additional engineered features such as Green Recovery or Thermorecovery systems that lyse the cell upon cessation of CO2 aeration. By engineering the cyanobacteria to \"process themselves\"" we reduce costs associated with energy intensive steps like centrifugation filtration or flocculation. Moreover the need for toxic or costly inducers/flocculating agents is minimized. Potential Applications: 1) Algaculture - increased output of useful products: Fatty acids biofuels fine chemicals bioplastics isprene D-lactate hydrogen etc. 2) Bioremediation - sediment and pollutants can be trapped and precipitated with the agglutinated biomass 3) Agricultural feed/fertilizers - made fromt he discarded biomass 4) Applicable to the Green Recovery (AzTE Cases M11-015 & M12-068) technology by concentrating biomass and increasing the local concentration of lipolytic enzymes to enhance yields of recovered free fatty acids"


1) Autoagglutination reduces reliance on centrifugation filtration and flocculation 2) No need for toxic/costly additives 3) Applicable to a wide array of phototrophs 4) Promoters are stimulated by low cost/free stimuli such as: inorganic carbon limitation high or low light intensity growth phase cell density temperature etc. 5) Compact production - currrent technologies require vast quantities of farmland to produce feedstocks; cyanobacterial aquaculture has low space and energy requirements and does not compete with food production

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