title: Molasses as fermentation substrate for levan production by Halomonas sp.
abstract: Levan is a homopolymer of fructose with many outstanding properties like high solubility in oil and water, strong adhesiveness, good biocompatibility, and film-forming ability. However, its industrial use has long been hampered by costly production processes which rely on mesophilic bacteria and plants. Recently, Halomonas sp. AAD6 halophilic bacteria were found to be the only extremophilic species producing levan at high titers in semi-chemical medium containing sucrose, and in this study, pretreated sugar beet molasses and starch molasses were both found to be feasible substitutes for sucrose. Five different pretreatment methods and their combinations were applied to both molasses types. Biomass and levan concentrations reached by the Halomonas sp. AAD6 cells cultivated on 30 g/L of pretreated beet molasses were 6.09 g dry cells/L and 12.4 g/L, respectively. When compared with literature, Halomonas sp. was found to stand out with its exceptionally high levan production yields on available fructose. Molecular characterization and monosaccharide composition studies confirmed levan-type fructan structure of the biopolymers. Rheological properties under different conditions pointed to the typical characteristics of low viscosity and pseudoplastic behaviors of the levan polymers. Moreover, levan polymer produced from molasses showed high biocompatibility and affinity with both cancerous and non-cancerous cell lines.
authors.affiliation: Institute of Environmental Sciences, Boğaziçi University, Istanbul, Turkey.
authors.forename: Faruk
authors.initials: F
authors.lastname: Küçükaşik
authors.forename: Hande
authors.initials: H
authors.lastname: Kazak
authors.forename: Dilvin
authors.initials: D
authors.lastname: Güney
authors.forename: Ilaria
authors.initials: I
authors.lastname: Finore
authors.forename: Annarita
authors.initials: A
authors.lastname: Poli
authors.forename: Orhan
authors.initials: O
authors.lastname: Yenigün
authors.forename: Barbara
authors.initials: B
authors.lastname: Nicolaus
authors.forename: Ebru Toksoy
authors.initials: ET
authors.lastname: Oner
mesh_terms: D027461:Beta vulgaris / Q000737:chemistry* / Q000378:metabolism*; D018533:Biomass; D005285:Fermentation; D005630:Fructans / Q000378:metabolism*; D020632:Halomonas / Q000254:growth & development / Q000378:metabolism*; D008965:Molasses
chemical_list: D005630:Fructans; C072599:levan