Study of light requirements of a Photobioreactor

Abstract

Photobioreactors are used to grow photosynthetic cell cultures. Many factors influence the growth of cell cultures such as light, carbon dioxide, and nutrients. To design a photobioreactor (PBR) an understanding of the light requirements for microalgae is necessary. It is known that photosynthetic microalgae need light, but the intensity and length of exposure for optimal biomass production is not known. Efficient PBR design requires that light be provided at the required intensities, duration and wavelength based on pigments present in the microalgae. An excessive intensity may lead to photoinhibition and photooxidation while low intensities may not promote algal growth. Long exposure to light may lead to minor damage of algal collection antenna that can be quickly repaired by the cell if placed in the dark. Photosynthesis is a process that takes time and once the process is initiated, additional photon energy collected will be lost as thermal energy. Photons that are collected, but not at the appropriate energy (wavelength) will be inefficient for photosynthesis. If the photon has too little energy, it will be likely lost as thermal energy. Temperature of medium is also influences the light intensity requirements for optimal growth. Factors effecting selection and design of light source are discussed as well as the interaction of the factors.