Photonic-chemostat engineering for efficient continuous cultivation of cyanobacteria
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Published version
Author(s)
Rahman, Mohammad Redwanur
Noori, Md Tabish
Hellgardt, Klaus
Noori, Md Tabish
Type
Journal Article
Abstract
Optimising continuous phototrophic cultivation remains a major challenge for scalable, energy-efficient cyanobacterial bioprocesses. Here, we combine controlled photophysiology, long-term continuous experimentation, multi-parameter analysis, and batch-derived Monod kinetic modelling to define a precise operational window for Synechocystis sp. PCC
6803 under flat-plate photobioreactor (FP-PBR) illumination. Using a fully calibrated FP-PBR platform, we first quantified intrinsic growth limits (µmax
= 0.081–0.118 day−1) across low, moderate, and high irradiance regimes, establishing the illumination-driven growth ceilings that constrain downstream continuous operation. Guided by these kinetic boundaries, continuous cultivation demonstrated that productive steady-state growth emerges only within a narrow regime governed by light intensity (500–700 µmol photons m−2 s−1 ), temperature (32–34 °C), and dilution rate (0.12–0.14 day−1). Single-parameter and 3D interaction analyses revealed strong coupling between photonic supply, thermal sensitivity, and hydraulic residence time, while multi-factor modelling captured these nonlinear constraints and accurately predicted washout boundaries. Translating these insights into sustainability metrics, the optimised regime supports 0.07–0.125 g L−1 day−1 of biomass productivity, equivalent to 8.4–15.0 g biomass day−1 and 176–315 kJ
day−1 of chemical energy in a 120 L mini-pilot system. Stoichiometric analysis indicates this corresponds to 15.6–27.6 g CO2 day−1 sequestered, demonstrating measurable environmental benefit even at a small scale. Together, these results provide a mechanistically grounded, kinetically constrained framework for designing inherently efficient, low waste, and model-predictive cyanobacterial photobioprocesses aligned with green chemistry and future carbon-neutral
manufacturing.
6803 under flat-plate photobioreactor (FP-PBR) illumination. Using a fully calibrated FP-PBR platform, we first quantified intrinsic growth limits (µmax
= 0.081–0.118 day−1) across low, moderate, and high irradiance regimes, establishing the illumination-driven growth ceilings that constrain downstream continuous operation. Guided by these kinetic boundaries, continuous cultivation demonstrated that productive steady-state growth emerges only within a narrow regime governed by light intensity (500–700 µmol photons m−2 s−1 ), temperature (32–34 °C), and dilution rate (0.12–0.14 day−1). Single-parameter and 3D interaction analyses revealed strong coupling between photonic supply, thermal sensitivity, and hydraulic residence time, while multi-factor modelling captured these nonlinear constraints and accurately predicted washout boundaries. Translating these insights into sustainability metrics, the optimised regime supports 0.07–0.125 g L−1 day−1 of biomass productivity, equivalent to 8.4–15.0 g biomass day−1 and 176–315 kJ
day−1 of chemical energy in a 120 L mini-pilot system. Stoichiometric analysis indicates this corresponds to 15.6–27.6 g CO2 day−1 sequestered, demonstrating measurable environmental benefit even at a small scale. Together, these results provide a mechanistically grounded, kinetically constrained framework for designing inherently efficient, low waste, and model-predictive cyanobacterial photobioprocesses aligned with green chemistry and future carbon-neutral
manufacturing.
Date Issued
2026-02-25
Date Acceptance
2026-02-18
Citation
RSC Advances, 2026, 16, pp.11036-11048
ISSN
2046-2069
Publisher
The Royal Society of Chemistry
Start Page
11036
End Page
11048
Journal / Book Title
RSC Advances
Volume
16
Copyright Statement
© 2026 The Author(s). Published by the Royal Society of Chemistry. Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
License URL
Publication Status
Published
Date Publish Online
2026-02-26