Use of wavelength-selective optical light filters for enhanced microalgal growth in different algal cultivation systems

• Nano-material light filters were used to filter certain spectrum of wavelengths.
• The light filters improved algal yield for 13–34% in flat panel photobioreactors.
• The light filters improved algal productivity for 70–100% in attached growth system.
• The light filters show a great potential to be used in large-scale algal production.

This work is to use thin film nano-materials as light filters to selectively transmit certain wavelengths from natural sunlight to algal culture. A red light filter (620–710 nm) and blue filter (450–495 nm) were evaluated. Algae were grown in flasks, flat panel reactors, and rotating algal biofilm (RAB) system. It was found that the light filters did not improve algal growth in flask cultures, probably due to the additional reflection of light by the glass wall of the flasks. However, the light filters significantly (P < 0.05) improved biomass yield (13–34%) in flat panel reactors and biomass productivity (70–100%) in RAB system, depending on the growth mode and lighter filters. Such improvements may be due to the eliminating the ultra-violet (UV) damaging the cellular structure. The biomass compositions did not change significantly among different light-filter cultures (P > 0.05). The research shows a great potential of using light filters to improve microalgal growth.