This STTR Phase I project proposes to develop and establish a novel clumping (flocculation) strain of algal using an engineered extracellar protein that can be induced. The overarching goal is to provide the industry with a novel, energy efficient, and cost effective tool to dewater microalgae.
What are the broader/commercial impacts of the proposed project? The broader/commercial impact of the proposed project will be an algal strain that, under controlled conditions, will self associate and eliminate the need for costly harvesting technologies. In addition, the results of this project will contribute to genetic engineering technology application to algal biomass, reduce costs of algae harvesting, and provide the society with a cost-effective green energy source.
The primary objective of this proposal was to enhance the process by which microalgae are harvested in order to lower the overall cost of producing biofuels from algae. The prohibitively high cost of producing renewable biofuels from algal lipids is due, at least in part, to the high cost of removing the biomass from the water column (harvesting and dewatering). Existing technologies proposed for harvesting algae on a commercial-scale are exceedingly expensive and this grant specifically sought to alleviate that fact. The investigators attempted to use the tools of molecular biology to produce two different algal strains that each display a different, but complementary, affinity protein on their cell surface which would promote the clumping, then settling of algae. In the natural lifecycle of C. reinhardtii two different affinity proteins, termed agglutinins, are expressed on different mating types. The associated agglutinins bind tightly to each other and ultimately enable algal cells to fuse together during reproduction. The technical goal of the research was to engineer two separate algal strains that always display one of the agglutinins on its cell surface. This would allow the altered strains to be cultured separately in different grow-out facilities. After maximum growth is achieved the two strains would be mixed together, resulting in binding between cells through the associations of the agglutinins and thus flocculate (clump together) and precipitate out of solution. This process would eliminate the need for the relatively expensive harvesting methods currently employed on pilot-level scales (e.g., high-speed centrifugation, chemical flocculating agents, diffused air floatation, etc.). Ultimately we validated our hypothesis using cross-linking antibodies against the mating proteins as an alternate approach. Using these surrogate antibodies we were able to demonstrate that engineered strains of microalgae producing complementary affinity proteins have the potential to cause clumping and reduce the cost of harvesting aquatic biomass as predicted. However, with insufficient time to resolve some technical challenges, an engineered strain of microalgae was not generated. As a positive fringe benefit, during the course of the grant, the Investigators also identified candidate genes in C. reinhardtii and gained considerable insight concerning their manipulation via molecular techniques. Although not part of the original grant, during the course of conducting this research several novel observations were made. Although preliminary the investigators believe they are significant and plan to pursue their elucidation in the future.
