Improved levan production by novel Calidifontibacillus erzurumensis LEV207 using one variable at a time approach

Abstract Levan, an exopolysaccharide, has applications in the medical and food sectors. Under natural conditions, levan is produced at a low concentration by microorganisms. This current study focuses on optimizing levan production by a one-variable-at-a-time approach from a novel marine bacterium, Calidifontibacillus erzurumensis LEV207. The growth and levansucrase production by C. erzurumensis LEV207 were studied to optimize the media components and conditions. Sucrose and yeast extract proved to be a good levansucrase inducer. The pH of 6.0 and temperature of 30°C, along with MgSO4 as salt, increased the enzyme activity. Sucrose and yeast extract at the concentration of 50% and 1%, respectively, produced the maximum enzyme activity of 427.4 µmol/mL/min after 48 hrs of incubation. The optimization process increased the levan (EPSLEV207) production 7-fold with a final yield of 65.58 g/L. To confirm the structure and nature of EPSLEV207, NMR and XRD were performed, and the functional groups present in EPSLEV207 were determined using FTIR. Chemical hydrolysis of levan confirmed fructose as the monomer, making EPSLEV207 a homopolysaccharide. EPSLEV207 exhibited 49% and 22% radical scavenging activity against DPPH and ABTS radicals, respectively, and promoted the growth of probiotic strain. EPSLEV207 showed an 88% water solubility index and 78% water retention capacity. The optimization process has increased the yield of levan up to 7-fold, highlighting the potential of C. erzurumensis LEV207 to be a viable option for industrial applications.