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Light-field-characterization in a continuous hydrogen-producing photobioreactor by optical simulation and
Felix Krujatz1, Rico Illing2, Tobias Krautwer3
1Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany. Felix.Krujatz@tu-dresden.de.
Biotechnology and Bioengineering
|June 4, 2015
Summary
Optimizing photobioreactor conditions for hydrogen production by Rhodobacter sphaeroides DSM 158 is key for bioenergy. Moderate turbulence and fluctuating light in continuous culture maximize photofermentative hydrogen production (rH2).
Area of Science:
- Photobiotechnology
- Bioenergy research
- Microbial hydrogen production
Background:
- Externally illuminated photobioreactors (PBRs) are crucial for phototrophic microorganisms in bioenergy and photobiotechnology.
- Understanding fluid flow effects on light distribution is vital for optimizing PBR performance.
Purpose of the Study:
- To simulate and describe how fluid flow conditions in a continuous hydrogen-producing PBR affect the rate of photofermentative hydrogen production (rH2).
- To identify optimal conditions for maximizing rH2 by Rhodobacter sphaeroides DSM 158.
Main Methods:
- Optical ray tracing (ZEMAX) to quantify light intensity within the PBR.
- Empirical three-parametric model for light attenuation in dense cultures.
- Computational Fluid Dynamics (CFD) and Particle Tracing (COMSOL Multiphysics) to visualize fluid flow and cellular trajectories.
Main Results:
- 24.2% of emitted light energy was lost due to optical effects or did not reach the PBR surface.
- Light intensity was fully attenuated within 1 cm of the PBR radius in dense cultures.
- Moderate turbulence (Reynolds number = 12,600) and 1.5 Hz fluctuating illumination yielded the highest rH2 (170.5 mL L⁻¹ h⁻¹).
Conclusions:
- Bacterial movement and light exposure significantly impact hydrogen production rates.
- Optimized fluid dynamics and light fluctuation are critical for enhancing photofermentative hydrogen production in PBRs.
