Algae Biomass Summit
September 29 - October 2, 2015
Marriott Washington Wardman Park

Abstract of our presentation:
From optical properties of algae to novel photobioreactors
Michael Sandmann1,2, Marvin Münzberg1, Lena Bressel1, Roland Hass1, Julia Mießner1, Oliver Reich1

1University of Potsdam, Institute of Chemistry, Physical Chemistry – innoFSPEC, Am Mühlenberg 3, 14476 Potsdam, Germany
2Institute for Food and Environmental Research e.V., Arthur-Scheunert-Allee 40/41, 14558 Nuthetal, Germany

Algae are very promising candidates for renewable resources due to their superior photoautotrophic growth rates. Hence, optimization of the conditions for algal growth is the main interest of today’s research on photobioreactors (PBR). One of the most important parameters for photoautotrophic algal growth is the light distribution inside the PBR. Due to a concerted interplay between light consumption, scattering or production by the algal cells and the PBR itself, the light distribution changes dynamically. Knowledge of these highly complex phenomena will hopefully lead to a fundamentally improved design of PBRs and process management.

In this work two different in-line fiber-optical technologies are presented, which have been established for biotechnological applications and are well suited for studying the light distribution and algal biomass growth in a PBR:
(1) A light sensing approach was established to monitor the light distribution inside the PBR during algal cultivation. In this setup 144 optical fibers were used as point-like passive sensors guiding light from various positions in the PBR to a spectrometer and thus providing access to the temporally, spatially and spectrally resolved light distribution in the PBR.
(2) Photon Density Wave (PDW) spectroscopy, a technique based on multiple light scattering, that enables the independent and absolute determination of physical key parameters (absorption and reduced scattering coefficient) of concentrated algal suspensions. It therefore allows for monitoring of biomass content changes inside the PBR. Measurements were carried out continuously over a time period of several weeks with sub minute time resolution. The technique was applied directly in the highly concentrated algal suspension in the reactor without any need of sampling or sample preparation.

Both techniques were applied on a novel ultra-thin layer PBR, which allows peak biomass concentrations of more than 35 g dry matter / L and biomass productivities of 3-5 g dry matter / (L*day) during outdoor production. The new reactor in combination with the fiber-optical approaches will lead to an increased process intensification and a better process management.