title: Inhibition of alkaline flocculation by algal organic matter for Chlorella vulgaris.
abstract: Alkaline flocculation is a promising strategy for the concentration of microalgae for bulk biomass production. However, previous studies have shown that biological changes during the cultivation negatively affect flocculation efficiency. The influence of changes in cell properties and in the quality and composition of algal organic matter (AOM) were studied using Chlorella vulgaris as a model species. In batch cultivation, flocculation was increasingly inhibited over time and mainly influenced by changes in medium composition, rather than biological changes at the cell surface. Total carbohydrate content of the organic matter fraction sized bigger than 3 kDa increased over time and this fraction was shown to be mainly responsible for the inhibition of alkaline flocculation. The monosaccharide identification of this fraction mainly showed the presence of neutral and anionic monosaccharides. The addition of 30-50 mg L(-1) alginic acid, as a model for anionic carbohydrate polymers containing uronic acids, resulted in a complete inhibition of flocculation. These results suggest that inhibition of alkaline flocculation was caused by interaction of anionic polysaccharides leading to an increased flocculant demand over time.
authors.affiliation: KU Leuven Kulak, Laboratory of Aquatic Biology, E. Sabbelaan 53, B-8500 Kortrijk, Belgium. Electronic address: dries.vandamme@kuleuven-kulak.be.
authors.forename: Dries
authors.initials: D
authors.lastname: Vandamme
authors.affiliation: KU Leuven Kulak, Laboratory of Aquatic Biology, E. Sabbelaan 53, B-8500 Kortrijk, Belgium.
authors.forename: Annelies
authors.initials: A
authors.lastname: Beuckels
authors.affiliation: National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Vadelius
authors.affiliation: KU Leuven Kulak, Laboratory of Aquatic Biology, E. Sabbelaan 53, B-8500 Kortrijk, Belgium.
authors.forename: Orily
authors.initials: O
authors.lastname: Depraetere
authors.affiliation: IRF Life Siences, KU Leuven Kulak, E. Sabbelaan 53, B-8500 Kortrijk, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Noppe
authors.affiliation: KU Leuven, Campus Groep T Leuven, Faculteit Industriële Ingenieurswetenschappen, Andreas Vesaliusstraat 13, B-3000 Leuven, Belgium.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Dutta
authors.affiliation: KU Leuven Kulak, Research Unit Food & Lipids, Department of Molecular and Microbial Systems Kulak, Etienne Sabbelaan 53, B-8500 Kortrijk, Belgium; Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium.
authors.forename: Imogen
authors.initials: I
authors.lastname: Foubert
authors.affiliation: National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA.
authors.forename: Lieve
authors.initials: L
authors.lastname: Laurens
authors.affiliation: KU Leuven Kulak, Laboratory of Aquatic Biology, E. Sabbelaan 53, B-8500 Kortrijk, Belgium.
authors.forename: Koenraad
authors.initials: K
authors.lastname: Muylaert
mesh_terms: D000464:Alginates / Q000494:pharmacology; D018533:Biomass; D048408:Chlorella vulgaris / Q000737:chemistry* / Q000187:drug effects / Q000502:physiology*; D003470:Culture Media / Q000737:chemistry; D005427:Flocculation; D020723:Glucuronic Acid / Q000494:pharmacology; D006603:Hexuronic Acids / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D058086:Microalgae; D011134:Polysaccharides / Q000378:metabolism; D012972:Sodium Hydroxide / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000464:Alginates; D003470:Culture Media; D006603:Hexuronic Acids; D011134:Polysaccharides; D012972:Sodium Hydroxide; D020723:Glucuronic Acid
keywords: Biofuels; Coagulation; Dissolved organic matter; Extracellular polymeric substances; Harvesting; Microalgae