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.

Levan-Producing Leuconostoc citreum Strain BD1707 and Its Growth in Tomato Juice Supplemented with Sucrose

“…The FTIR spectrum of BD1707 fructan well matched the characteristic peaks in the spectra of levan derived from Halomonas sp. strain AAD6 (28), indicating that the two polysaccharides shared similar structures. The ␤-(2¡6) linkages in BD1707 fructan were further confirmed by 1 H and 13 C NMR analysis.…”

Enhanced l-lysine production from pretreated beet molasses by engineered Escherichia coli in fed-batch fermentation

“…For example, Roukas [13] found that tricalcium phosphate treatment could effectively reduce the concentration of heavy metals in beet molasses, resulting in maximum biomass production and better results with respect to polysaccharide concentration, polysaccharide yield, and sugar utilization. Furthermore, Küçükaşik et al [8] compared the effects of eight different molasses pretreatment methods on the cell growth of Halomonas sp. AAD6 and levan production and found that approximately 90 % of the pigment substances and excess metal ions (nickel, zinc) in beet molasses were removed by combined pretreatment with tricalcium phosphate, sulfuric acid, and activated carbon, which resulted in highest biomass and levan concentrations.…”

“…Previous studies have shown that some chemical substances, such as pigment substances, suspended colloids, excessive metallic ions, and ash, are inevitably generated during molasses refining processes, which could inhibit the growth of microorganisms, influence the pH of the substrate, and inactivate the enzymes associated with the biosynthesis of the product [8,12,13], decreasing the levels of biomass and biochemicals produced. Hence, various pretreatment methods that could selectively remove these hazardous components and fermentation conditions have been examined to optimize microbial growth and biochemical production.…”

“…To date, molasses has been used to effectively produce L-lactic acid [5], ethanol [6], succinic acid [7], levan [8], benzaldehyde lyase [9]. Despite recent advances, several issues remain which limit molasses fermentation processes.…”

Proteaz ve Biyopestisit Üretimlerinin Eşzamanlı Optimizasyonu: Endüstriyel Bakış Açısında Bir Durum Çalışması

“…The diluted molasses was centrifuged at 8.000 rpm for 20 min. The supernatant was separated from the undesirable remains [25]. CSL was prepared at 2% (w/v), and the pH of the solution was adjusted to 7.0 using 1 M KOH.…”