An integrated wavelength-shifting strategy for enhancement of microalgal growth rate in PMMA- and polycarbonate-based photobioreactors

Abstract

This study investigates the spectral shifting of UV-A radiation, using fluorescent material, as a tool for enhancing Chlorella sp. growth rate in simulated photobioreactors made of UV-stabilized polycarbonate (PC) and poly (methyl methacrylate) (PMMA). The feasibility of using a fluorescent coating as a wavelength shifter layer, to shift UV-A radiation to the PAR range, was explored. For this purpose, a variety of concentrations of fluorescent dye dissolved in thermoplastic acrylic resin were prepared and used to coat PMMA and PC sheets which then were placed between the radiation source and the culture flask. Compared with the uncoated sheets, the panels coated with the wavelength shifter layer exhibited 74% and 45% (for PC and PMMA substrates, respectively) increase in biomass productivity during the same culture period. It was also found that the elimination of UV-A radiation increased chlorophyll a content of the cells.

Key words:

• biomass productivity
• fluorescent dye
• microalgae
• photosynthetically active radiation
• UV-A

Acknowledgements

We would like to thank Dr Madanipour and Mr Hosseini from the Optical Measurement Central Laboratory of the Optics, Laser & Photonics Institute of Amirkabir University of Technology for assisting us with light-measuring devices and methods. Also, the effort of Ms Nejadebrahim in making the wavelength-shifter sheets is gratefully acknowledged.