Light Regime Characterization in an Airlift Photobioreactor for Production of Microalgae with High Starch Content

Abstract

The slow development of microalgal biotechnology is due to the failure in the design of large-scale photobioreactors (PBRs) where light energy is efficiently utilized. In this work, both the quality and the amount of light reaching a given point of the PBR were determined and correlated with cell density, light path length, and PBR geometry. This was made for two different geometries of the downcomer of an airlift PBR using optical fiber technology that allows to obtain information about quantitative and qualitative aspects of light patterns. This is important since the ability of microalgae to use the energy of photons is different, depending on the wavelength of the radiation. The results show that the circular geometry allows a more efficient light penetration, especially in the locations with a higher radial coordinate (r) when compared to the plane geometry; these observations were confirmed by the occurrence of a higher fraction of illuminated volume of the PBR for this geometry. An equation is proposed to correlate the relative light intensity with the penetration distance for both geometries and different microalgae cell concentrations. It was shown that the attenuation of light intensity is dependent on its wavelength, cell concentration, geometry of PBR, and the penetration distance of light.

Calculation of the radiative properties of photosynthetic microorganisms

“…In the light of this gap, numerous research groups have no alternatives but to make use of the empirical tools developed by the community over the past 20 years [20][21][22][23][24][25]10]. These tools are based on radically different modelling approaches from the one that we develop hereafter.…”

Metabolic network reconstruction of Chlamydomonas offers insight into light‐driven algal metabolism

“…Commercial use and basic scientific research of photosynthetic organisms could benefit from better understanding of how light is absorbed and affects cellular systems. The quality of light sources implemented in photobioreactors largely determines the efficiency of energy usage in industrial algal farming (Fernandes et al , 2010). Light spectral quality also affects how photon absorption induces various metabolic processes: photosynthesis, pigment and vitamin synthesis, and the retinol pathway required for phototaxis.…”

Nutrient limitation as a strategy for increasing starch accumulation in microalgae

“…Nowadays, microalgae are considered as one of the most promissory renewable feedstock for biofuels production because of several advantages, such as: faster growth, higher photosynthetic efficiency and biomass production compared to other energy crops [5][6][7][8]. The microalga Chlorella vulgaris, in particular, has been recognized as a potential feedstock for bioethanol production due to its capacity to accumulate high levels starch (up to 37% dry weight) [9].…”