A rapid assessment of the radiative properties from a suspension of Chromochloris zofingiensis

Abstract

Regardless if a kinetic expression of a light-dependent bioprocess is being sought, the parameters of that kinetic function are being adjusted, or a scaling-up process is being carried out to predict the productivity of a reactor, it is necessary to know the light availability in the culture volume. The emission characteristics of the radiation source, the geometry of the reactor as well as the optical properties of the suspension that resides within it must be known to achieve the latter. Here, we present an approach to quantify the optical properties of microalgae suspensions. A simple methodology, consisting in illuminating a suspension of microalgae with a characterised polychromatic radiation source and assessing how the directions are modified, and the amount of energy carried by the light beams after crossing the suspension, was successfully employed. Subsequently, through an optimisation program, the experimental culture data has been used to determine the spectral absorption and scattering coefficients of photons, and the suspension's scattering phase function. For a given microalgal culture, eight samples corresponding to a cultivation time of one week were analysed, utilising an energy balance, independently of the biomass or pigment concentration. Altogether the results presented here suggest that this methodology could be adapted to other suspensions, allowing accessible ways to evaluate the radiative characteristics of phototrophic microorganisms in the complex context of the evolution through time of the radiant energy field inside a photobioreactor.