A fully predictive model for one‐dimensional light attenuation by Chlamydomonas reinhardtii in a torus photobioreactor

Abstract

The light attenuation in a photobioreactor is determined using a fully predictive model. The optical properties were first calculated, using a data bank of the literature, from only the knowledge of pigments content, shape, and size distributions of cultivated cells which are a function of the physiology of the current species. The radiative properties of the biological turbid medium were then deduced using the exact Lorenz-Mie theory. This method is experimentally validated using a large-size integrating sphere photometer. The radiative properties are then used in a rectangular, one-dimensional two-flux model to predict radiant light attenuation in a photobioreactor, considering a quasi-collimated field of irradiance. Combination of this radiative model with the predictive determination of optical properties is finally validated by in situ measurement of attenuation profiles in a torus photobioreactor cultivating the microalgae Chlamydomonas reinhardtii, after a complete and proper characterization of the incident light flux provided by the experimental set-up.

Quantifying bioalbedo: a new physically based model and discussion of empirical methods for characterising biological influence on ice and snow albedo

“…First, the complex refractive index of the cells must be known. The real part of the refractive index (representing refraction) is assumed to be constant for all cells at a value of 1.5 (Pottier et al, 2005), whereas the imaginary part of the refractive index (k λ , representing absorption) varies according to the pigmentation of the cells. This is modelled using a bio-optical scheme developed using Pottier et al's (2005) study of algal cells in bioreactors (also used by Cook et al, 2017) from user-defined values of pigment abundance (as % total cellular dry mass) according to…”

“…The water fraction (x w ) and density of cellular dry mass (ρ dm ) are assumed constant throughout the simulations presented in this paper (ρ dm = 1400 kg m −3 , x w = 0.8: Dauchet et al, 2015); however, we provide Eq. (2) to enable derivation of x w from empirical data (see Pottier et al, 2005;Kandilian et al, 2016). It should be noted that there are limits of applicability for Eq.…”

“…Other groups have examined snow algae from a biological perspective. Remias et al (2005Remias et al ( , 2010 showed that snow algae produce pigments in response to environmental stresses that changes their colour and thereby influence snow albedo. Hodson et al (2017) also documented how both surface and subsurface algal populations influenced the optical properties of maritime Antarctic snow.…”

“…This was discussed by Yallop et al (2012) who linked algal pigmentation to ice albedo in south-western Greenland but did not explicitly identify the pigments responsible. Ice algae produce a range of pigments to facilitate both light harvesting across the visible spectrum and energy dissipation under conditions of excessive irradiance (Remias et al, 2009) via, for example, the interconversion of xanthophyll pigments to quench excess excitation energy as heat (Niyogi et al, 1997;Goss and Jakob, 2010). In addition, ice algae inhabiting surface habitats produce specialist UV-absorbing pigments (purpurogallins) that are distinct from the typical UV-absorbing pigments (mycosporine-like amino acids) identified in other algal lineages (Remias et al, 2012).…”

Technical insight on the requirements for CO2-saturated growth of microalgae in photobioreactors

“…Light, which drives the photochemical reactions to produce usable energy for carbon fixation in algal photosynthesis, has been researched utmost to maximize the rate of photosynthesis in photobioreactors, where the cells are often light-limited due to self shading (Olivieri et al 2014). Mathematical models of photosynthesis-light relationship, description of light regime (periodic variations in light intensity experienced by individual cells as they traverse through light gradient inside culture), and prediction of photosynthetic response to light regime are the cornerstones of photobioreactor engineering (Brindley et al 2011;Fernández et al 1997;Molina-Grima et al 1999;Merchuk et al 2007;Pottier et al 2005;Pruvost et al 2008;Yun and Park 2003). Carbon dioxide-the carbon source-is another crucial factor affecting photoautotrophic growth.…”