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KMID : 1094720210260030483
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Biotechnology and Bioprocess Engineering
2021 Volume.26 No. 3 p.483 ~ p.500
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Improvements in Conventional Modeling Practices for Effective Simulation and Understanding of Microalgal Growth in Photobioreactors: an Experimental Study
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Yuvraj
Padmanabhan Padmini
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Abstract
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This work identifies shortcomings of conventional practices in unstructured modeling of microalgal growth, thereby exploring the possibility of improving simulation of algal cultures. Light- and nitrogen-limited growth of Chlorella vulgaris under CO2-replete conditions was modeled and simulated for a series of operating conditions in stirred-tank photobioreactors of bench scale. Based on the response of alga over a wide range of incident fluxes (50?400 μmol/(m2·s)) and nitrate levels (23?720 mg/L) in bubbled culture tubes, sixteen two-factor multiplicative models were developed by coupling suitable single-factor kinetic models for light and nitrate limited growth. Results suggest that the traditional use of Monod and Andrews kinetics in multi-factor modeling may not always be optimum as growth of the microalga was best described by other common models with a R2 of 0.93. Contrary to common belief, the study has demonstrated that biomass yield on nitrogen is a variable quantity and its reciprocal can be precisely modeled by Logistic/Gompertz function of nitrogen concentration. Common schemes to determine growth rate in attenuated light were also assessed. Local growth rates were found more appropriate than average intensity for estimation of net growth rate in steep light gradients. Simulations have also revealed that dissolved oxygen tension as high as 400% does not possess any threat to microalgal cultures as generally assumed. Model’s predictability for scaled culture in geometrically similar photobioreactor was also examined.
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KEYWORD
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microalgae, growth modeling, dynamic simulation, Chlorella vulgaris, photobioreactor
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