title: Light-field-characterization in a continuous hydrogen-producing photobioreactor by optical simulation and computational fluid dynamics.
abstract: Externally illuminated photobioreactors (PBRs) are widely used in studies on the use of phototrophic microorganisms as sources of bioenergy and other photobiotechnology research. In this work, straightforward simulation techniques were used to describe effects of varying fluid flow conditions in a continuous hydrogen-producing PBR on the rate of photofermentative hydrogen production (rH2 ) by Rhodobacter sphaeroides DSM 158. A ZEMAX optical ray tracing simulation was performed to quantify the illumination intensity reaching the interior of the cylindrical PBR vessel. 24.2% of the emitted energy was lost through optical effects, or did not reach the PBR surface. In a dense culture of continuously producing bacteria during chemostatic cultivation, the illumination intensity became completely attenuated within the first centimeter of the PBR radius as described by an empirical three-parametric model implemented in Mathcad. The bacterial movement in chemostatic steady-state conditions was influenced by varying the fluid Reynolds number. The "Computational Fluid Dynamics" and "Particle Tracing" tools of COMSOL Multiphysics were used to visualize the fluid flow pattern and cellular trajectories through well-illuminated zones near the PBR periphery and dark zones in the center of the PBR. A moderate turbulence (Reynolds number = 12,600) and fluctuating illumination of 1.5 Hz were found to yield the highest continuous rH2 by R. sphaeroides DSM 158 (170.5 mL L(-1) h(-1) ) in this study.
authors.affiliation: Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany. Felix.Krujatz@tu-dresden.de.
authors.forename: Felix
authors.initials: F
authors.lastname: Krujatz
authors.affiliation: Institute for Materials Science and Max Bergmann Center of Biomaterials and Center for Advancing Electronics Dresden, TU Dresden, Dresden, Germany.
authors.forename: Rico
authors.initials: R
authors.lastname: Illing
authors.affiliation: Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Krautwer
authors.affiliation: Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany.
authors.forename: Jing
authors.initials: J
authors.lastname: Liao
authors.affiliation: Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Helbig
authors.affiliation: Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Goy
authors.affiliation: Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Opitz
authors.affiliation: Institute for Materials Science and Max Bergmann Center of Biomaterials and Center for Advancing Electronics Dresden, TU Dresden, Dresden, Germany.
authors.forename: Gianaurelio
authors.initials: G
authors.lastname: Cuniberti
authors.affiliation: Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bley
authors.affiliation: Instituteof Food Technology and Bioprocess Engineering, TU Dresden, 01062 Dresden, Germany.
authors.forename: Jost
authors.initials: J
authors.lastname: Weber
mesh_terms: D055598:Chemical Phenomena; D057446:Hydrodynamics; D006859:Hydrogen / Q000378:metabolism*; D008027:Light; D058433:Photobioreactors / Q000382:microbiology*; D012242:Rhodobacter sphaeroides / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D006859:Hydrogen
keywords: computational fluid dynamics; hydrogen; optical ray tracing; particle tracing; photobioreactor