Scenedesmus obtusiusculus Harvesting by Flocculation

Felix Bracharz1, Frank Bohnen2, Farah Qoura1 and Thomas Brück1

1TUM · Industrial Biocatalysis ·www.ibc.ch.tum.de 2BBSI UG (haftungsbeschränkt) · www.bb-si.de

Advanced Biomass Value

BBSI UG (haftungs-beschränkt)Kattowitzer Straße 34 51065 Köln www.bb-si.de

Sustainable Innovations BBSI invents and licenses innovative tech-nologies to reduce green-house gas emissi-ons. BBSI is an expert company in the areas of renewable technologies for energetic and material use of biomass.

BBSI’s consulting business involves techno-logy optimization for biotechnological and chemical processes.

More than 65% of all publications on Design- of-Experiments based biotechnological process engineering and optimization contain major issues and errors regarding modelling and interpretation*.

It can be more complex than you thought. Together we find the right answer for you!

*Based on 50 + recalculations by BBSI of peer-reviewed journal articles.

BǀBǀSI Sustainable Innovations

IBK: Expert for Industrial BiocatalysisThe research group “Industrial Biocatalysis” is focused on fundamental aspects of biocata-lysis and genetic engineering to understand and predict the basic molecular and structu-ral features that provide or impose industrial process fitness on biocatalytic systems.

Research involves novel biotechnological processes that utilize agricultural (i.e. Straw), forestry (i.e. wood residue) and food (i.e. crab shells) waste biomass as feedstocks for focu-sed biotransformations that yield industrially relevant chemical building blocks and rene- wable fuels. Waste Biomass streams do not compete with food production, are not asso- ciated with land use change or increased water utilization.

Harvesting and Dewatering steps can account for 20-30% of total micoalgal biomass cost. Small cell size, high colloidal stability and low biomass concentrations pose major challenges for these process steps. Flocculation – sedimentation is regarded as very efficient, however the process conditions depend on the selected microalgae strain, the specific flocculant, media composition, culti- vation time and cell density. Due to the large number of possible flocculation agents and numerous factors affec-ting this process step, the application of the Design-of- Experiments (DoE) methodology is a suitable tool to obtain an accurate description of optimal harvesting conditions.

Values for independent variables are determined by the design, consisting of the box- and star point as well as a multiple measurement of the center point.

Scenedesmus obtusiusculus Flocculation

Flocculation Optimization – With Design of Experiments

Microalgae suspensions are stabilized by a negative surface charge. To induce flocculation, this charge has to be overcome by neutralization, bridging, electrostatic patching or sweeping mechanism during the flocculation process.

An ANOVA is used to exclude insignificant effects and separate effects of the different dependent variables on the flocculation efficiency.

The generated model has predictive strength for floccu-lation efficiencies within the boundaries of the design.

The shown surfaces describe the Flocculation efficiency FE in dependence of the Bentonite, Chitosan and Base concentration.

Flocculation is evaluated by using a jar test. Flocculant is added to the sample, which is subsequently agitated and left for sedimentation. Quantification and sedimentation kinetics are evaluated photometrically while packing density is estimated optically.

SedimentationFlocculationScenedesmus obtusiusculus Cultivation

TUMIndustrial Biocatalysis

Lichtenbergstraße 4 85748 Garching

www.ibc.ch.tum.de