The stimulatory effect of mannitol on levan biosynthesis: Lessons from metabolic systems analysis of Halomonas smyrnensis AAD6^T

Abstract

Halomonas smyrnensis AAD(T) is a halophilic, gram-negative bacterium that can efficiently produce levan from sucrose as carbon source via levansucrase activity. However, systems-based approaches are required to further enhance its metabolic performance for industrial application. As an important step toward this goal, the genome-scale metabolic network of Chromohalobacter salexigens DSM3043, which is considered a model organism for halophilic bacteria, has been reconstructed based on its genome annotation, physiological information, and biochemical information. In the present work, the genome-scale metabolic network of C. salexigens was recruited, and refined via integration of the available biochemical, physiological, and phenotypic features of H. smyrnensis AAD6(T) . The generic metabolic model, which comprises 1,393 metabolites and 1,108 reactions, was then systematically analyzed in silico using constraints-based simulations. To elucidate the relationship between levan biosynthesis and other metabolic processes, an enzyme-graph representation of the metabolic network and a graph decomposition technique were employed. Using the concept of control effective fluxes, significant links between several metabolic processes and levan biosynthesis were estimated. The major finding was the elucidation of the stimulatory effect of mannitol on levan biosynthesis, which was further verified experimentally via supplementation of mannitol to the fermentation medium. The optimal concentration of 30 g/L mannitol supplemented to the 50 g/L sucrose-based medium resulted in a twofold increase in levan production in parallel with increased sucrose hydrolysis rate, accumulated extracellular glucose, and decreased fructose uptake rate.

Implications for public health demands alternatives to inorganic and synthetic flocculants: bioflocculants as important candidates

“…As bioflocculant production is associated with a precise gene cluster, the information of the genome sequence of bioflocculant microbes is certainly the essential point for the optimization of their biosynthesis through the molecular biology approach (Ates et al. , ). The production of bioflocculants is a genetically determined process and metabolic engineering is a powerful tool to improve metabolite productivity (Delbarre‐Ladrat et al.…”

Effective stimulating factors for microbial levan production by Halomonas smyrnensis AAD6T

“…Ternary blend films of chitosan, PEO and levan were also prepared to evaluate their morphological, thermo-mechanical, surface and biological properties (15). Moreover, the generic metabolic model of Halomonas smyrnensis AAD6 T was reconstructed to elucidate the relationship between levan biosynthesis and other metabolic processes (16). Recently, the producer strain has been identified as a novel species of the genus Halomonas and named as H. smyrnensis AAD6 T (17) and its whole genome sequence has been announced (18).…”

Exopolysaccharides from Prokaryotic Microorganisms—Promising Sources for White Biotechnology Processes

“…With metabolic system analysis of this generic metabolic model, significant improvement in levan yields was obtained. 80 …”