Microalgal kinetics — a guideline for photobioreactor design and process development

Abstract

Kinetics generally describes bio‐(chemical) reaction rates in dependence on substrate concentrations. Kinetics for microalgae is often adapted from heterotrophs and lacks mechanistic foundation, e.g. for light harvesting. Using and understanding kinetic equations as the representation of intracellular mechanisms is essential for reasonable comparisons and simulations of growth behavior. Summarizing growth kinetics in one equation does not yield reliable models. Piecewise linear or rational functions may mimic photosynthesis irradiance response curves, but fail to represent the mechanisms. Our modeling approach for photoautotrophic growth comprises physical and kinetic modules with mechanistic foundation extracted from the literature. Splitting the light submodel into the modules for light distribution, light absorption, and photosynthetic sugar production with independent parameters allows the transfer of kinetics between different reactor designs. The consecutive anabolism depends among others on nutrient concentrations. The nutrient uptake kinetics largely impacts carbon partitioning in the reviewed stoichiometry range of cellular constituents. Consecutive metabolic steps mask each other and demand a maximum value understandable as the minimum principle of growth. These fundamental modules need to be clearly distinguished, but may be modified or extended based on process conditions and progress in research. First, discussion of kinetics helps to understand the physiological situation, for which ranges of parameter values are given. Second, kinetics should be used for photobioreactor design, but also for gassing and nutrient optimization. Numerous examples are given for both aspects. Finally, measuring kinetics more comprehensively and precisely will help in improved process development.

Experimental and Model-Based Analysis to Optimize Microalgal Biomass Productivity in a Pilot-Scale Tubular Photobioreactor

“…. , 2.1 g X mol ph −1 reported in the literature (Zijffers et al, 2010;Dillschneider et al, 2013;Schediwy et al, 2019). The estimated parameter µ max = 1.56 d −1 is comparable also to µ max ranges between 0.86, .…”

“…; in particular effects on growth and biochemical composition have been reported (Pal et al, 2011;Wagenen et al, 2012;Wahidin et al, 2013). Here, the applied photobioreactor system sets specific conditions for the culture, e.g., with respect to photon availability (Schediwy et al, 2019).…”

“…The underlying relationships have been successfully applied and demonstrated in several publications (Bernard, 2011;Kliphuis et al, 2011;Blanken et al, 2016). Equation (4) applies only to light-limited growth conditions and was originally developed considering flat-panel photobioreactors (Schediwy et al, 2019). Therefore, the tubular reactor compartment is considered to be a flat-panel equivalent with an average light path length l ∅ (Equation 3).…”

Fast‐growing phototrophic microorganisms and the productivity of phototrophic cultures

“…To assess the productivity of a phototrophic culture, we follow established models of light-limited growth (Clark et al, 2018;Huisman et al, 2002;Martínez et al, 2018;Schediwy et al, 2019).…”

Process Engineering of Biopharmaceutical Production in Moss Bioreactors via Model-Based Description and Evaluation of Phytohormone Impact

“…Monod-like equations have been used to model growth kinetics in autotrophic processes, where light, the energy source, is considered a substrate ( Béchet et al, 2013 ). The growth kinetics of Physcomitrella under different light intensities suggested Han Model behavior ( Cerff and Posten, 2012b ; Schediwy et al, 2019 ); therefore, we incorporated Monod’s equation in the threshold model to explain the substrate consumption and specific growth rate ( Eq. (3) ).…”