Dial a wavelength for exploiting the algal cell factory

Microalgae can be exploited in a wide array of applications which include pharmaceuticals, nutraceuticals, food supplements, bioremediation and aquaculture. Most algae are photo-autotrophs, using light energy, CO2 and minimal nutrients, providing valuable by-products whilst sequestering waste CO2. They are of increasing interest as components of the Circular Economy as sustainable solutions for food, energy and water security using by-products from other industrial processes for nutrients. Scotland's renewable energy sector has potential to grow microalgae economically at scale for food and pharma feedstocks with lighting powered by surplus renewable electricity.
In response to these challenges, Xanthella Ltd. has developed a novel range of photo-bioreactors (PBRs) and controllers which enable density-mediated adjustment of light intensity for high productivity of microalgae. Enhancement of growth and high-value pigment composition is supported by data from a recently completed IBioIC studentship at RGU, and other studies, where dry biomass of microalgae exceeded 2g/L after 10 d. These PBRs are smart, scalable (1 L, 100 L, 1000 L) modular systems where the 1000 L units can be integrated at local/community level, to exploit surplus renewable energy and local nutrient streams (brewing, distillery, dairy, anaerobic digestion). This is of particular significance in rural locations in Scotland which are effectively generating renewable energy but contribution to the national grid is constrained resulting in surplus energy, e.g. in Orkney in 2017 curtailment cost the local community ~£1.2M in lost income. A system that could act as a buffer for excess energy and generate income would be a valuable solution.
The Pandora PBRTM (1000 L) has been developed within the ground-breaking projects ASLEE and ENBIO, supported by Scottish Government's Local Energy Challenge and Zero Waste Scotland and is the only system that allows both the growth of high value biomass (microalgae) and the balancing of the grid. The installation of 16 PBRs in Ardnamuchan, creating one of the largest PBR systems in the UK, will generate data to evaluate and validate the potential of this technology. However, CAPEX and OPEX are still relatively high for the Pandora units since they utilize bespoke, submersible lights. These light systems currently represent around 2/3 of the total PBR cost, while the power consumption for a 1 m3 PBR is 4.8 kWh (representing 75% of the OPEX), limited by current lighting efficiency. To enable better exploitation in algal biotechnology, advances in the lighting system are needed for more cost-effective growth and to target production of specific bioactive compounds for high-value biomass.