Optimising light wavelengths in algal bioreactors

With funding from IBioIC, researchers from St Andrews and Xanthella Ltd have undertaken a feasibility project to improve the production of industrial feedstocks by microalgae under solar illumination. The team developed an approach to modify the spectrum of sunlight in bioreactors used to grow algae, for recycling unused wavelengths and to inhibit the growth of bacteria.

Challenge

Bioreactors are the most efficient way to grow algae at industrial scale. They can optimise the nutrients and temperature to benefit specific microalgal strains. Solar-illuminated bioreactors however have some limitations: microalgae only use 50% of the visible light spectrum, while surplus infrared and UV light can cause unwanted heating of the bioreactors and damage to the algae. Photobioreactor developers Xanthella wanted to see if the light could be tailored to suit the microalgae better. They teamed up with Graham Turnbull’s group in the Centre for Biophotonics at the University of St Andrews to explore the potential to convert UV light to longer wavelengths more suited to the microalgae.

Solution

Solar light conversion

Prof. Turnbull’s team developed a novel material that could optimise the light transmission into Xanthella’s reactors. A thin fluorescent film efficiently converts damaging UV light- or unused visible wavelengths- into useful photosynthetically active radiation, The team also developed a tailored method to deposit this material so that production of the film could be scaled up. Devices generating blue light successfully inhibited bacterial growth when used with UV lights, but also inhibited algal growth. The team therefore turned to testing the films with LED lights, which produced promising results.

Outcome

Future algal bioreactor lighting

The feasibility study identified new target wavelengths for photodynamic control in bioreactors, and future development routes for spectral control in solar- and LED-lit bioreactors.  The project partners have also developed a good working relationship, and a collaboration of Xanthella, St Andrews and Robert Gordon Universities is continuing to develop smart lighting technologies for bioreactors through an IBioIC-funded Collaborative Training Partnership project.

“This IBioIC project has enabled us both to identify new opportunities for our lighting technologies in the biotech sector, and to develop an enduring collaboration with Xanthella”