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The D-Factory project leaves behind a powerful legacy as to what constitutes a sustainable CO2 microalgal biorefinery

The €10million D-Factory Microalgal Biorefinery project supported by the E.C has now concluded, after 4 years of intensive collaboration between 14 partners from 9 different countries led by the University of Greenwich. Together the partner teams have sought to understand the requirements for establishing a sustainable microalgal value chain in its entirety, from algae cultivation to products and then to deliver it.

Throughout this ambitious project, great emphasis has been placed on developing sustainable technologies that could optimise production of halotolerant microalgae, by cultivating them using waste CO2 to reduce carbon emissions in all-year-round large-scale production systems, and on understanding how to tailor the quality of the algal biomass for lowest-cost product development. Then, in order to process the material for possible products, the team needed to specifically develop new technologies but without the full market understanding of what products would be sought by customers or the level of consumption. The alga Dunaliella salina was chosen because it grows well in highly saline non-potable water across the globe. Using well-established open pond raceway cultivation systems, the team was able to develop techniques to double the productivity of the alga using newly designed raceways constructed at the NBT production site in Eilat, then transfer the knowhow to cultivate natural strains of halophytic Dunaliella in open pond raceways at the demonstration site in Monzón, Spain. An Integrated Assessment of Sustainability of a CO2 Microalgal Biorefinery conducted by specialists in the team found that the practice of integrating algal cultivation with salt activities; using flue gas and waste heat from a power plant; avoiding using arable land and guaranteeing sufficient availability of freshwater would improve sustainability and this know-how is now demonstrated to a very high standard by the team based at Monzón. Here, the algal strains are cultivated in brine, which is sourced from shallow underground salt deposits infused with freshwater. The raceways are lined and fitted with paddlewheels, and also have a heating system for temperature control in winter. To increase the density of algae used to inoculate the ponds, closed photobioreactor systems were developed by the team, and to reduce costs in cultivation and effluent management a new harvesting system to harvest the algae intact instead of broken was developed. At this point the team needed to focus on developing products with high added-value. Dunaliella salina is the richest source of natural orange, yellow or red pigmented carotenoids known and consequently represented an ideal starting point for producing extracts of natural colorants as well as a range of natural carotenoid isomers for treating atherosclerosis, diabetes, psoriasis and ophthalmologic diseases. New processes based on supercritical CO2 extraction of the biomass were developed, and these now provide extracts rich in natural carotenes along with a defatted powder. The extract is being tested to lay the foundations for future clinical trials to show the value of one of the more unusual carotenes, 9-cis β-carotene. It has also been formulated for use in different beverage-type applications. The defatted powder on the other hand shows great promise in tests as a feed additive and also as a protein-rich bulking agent in fish sausages, and the individual starch, polar lipids and protein fractions have been processed as food additives, emulsifiers, and in gluten-free protein-enriched bread. However, there are still many challenges ahead, especially in separating pure carotenoid isomers in scale-up to produce sufficient stable sample preparations. To help overcome this problem members of the team have developed a novel, unique method to cultivate Dunaliella with a very high concentration of carotenes especially 9-cis -carotene. This technique offers specific benefits for low-cost, facile extraction of a valued carotene blend that will be more readily incorporated into foods as a natural colorant, than any other natural carotene preparation currently available on the market and, at the same time, impart health benefits that are superior to any other known carotene-based colorant.

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